Abstract
Mortality data of Taiwan for 1981 through 1986 were analyzed using three difierent statistics in order to assess the role of environmental and tifestyle factors in causing mortality variations. Infant mortality rates from different geographic regions generally correlated well with overall mortality from all ages, suggesting that there are many common risk factors affecting the entire age range of the population. The mortality rates of tobacco- and alcohol-related causes of death and cancers were much higher in males than females. A numberofcancer sites, including the lung, the Liver, the stomach, and the oasopharynx, showed more than twofold excesses in males. In contrast, females had a tenfold excessof genital cancer and a 33%higher rate of diabetes. With rapid industrialization, occupational hazards played an increasing role in the development of cancer and other causes of death. During the study period, fishermen showed increased risk for cancers of the stomach, the esophagus, and the liver, while construction workers had an increased risk for cancer of the esophagus. Peasants and soldiers bad an elevated suicide mortality. Among apprentices, fatal injuries were high. Findings h m this study are useful in setting priorities for health and safety programs and directing efforts such as health education programs and other preventive strategies against disease. Asia Pac J Public Health 1992A993;6(4):217-25.
Keywords: Cancer, gender gap, infant mortality, occupational hazards.
Address for Reprints: Dr chi-Pang Wen Institute of Biomcdid Scicnms,Academia
Sinica, Taipei,Taiwan,ROC.
Mortality Experience in a Rapidly Developing Economy in Taiwan: Infant Mortality, Gender Gap, and Occupational Risks Chi-Pang Wen, MD, P h D Shu-Fang Tsai, M P H Shan-Pou Tsai, PhD Institute of Biomedical Sciences Academia Sinica Taipei, Taiwan ROC Introduction Oneofthe most important featuresof epidemiological research is to study variations in disease distribution. We can unmask the causative factors and explore preventive measures by identifying environmental characteristics shared by not only those with high frequency of disease but also those with low prevalence of disease. In reviewing the mortality data of Taiwan, there are three areas of mortalityvariation that havenot been addressed in previous papers'-3 but are believed to contribute significantlyto the understanding ofthe environmental factors on mortality in Taiwan. They are Variations in infant mortality, differences in the male/female gender gap, and risks from OCCUpational hazards. a Infant has great deal Of attention because it Can be used as an index of health care quality- It is a good indicator of the socioeconomic development ofa geographicarea' aswellasa Yardstick for evaluating the degree of Success in Several areas such as prenatal Care, quality of child health services, and nutritional adequacy of the newborn. Mortality rates for males are quite different from those for females. The gender gap or sex differentials in mortality have long been recognized
in epidemiological literatures*6.Since malesand femalesare biologicallydistinct entities and mortality rates between these populations are widely varied, data are usually Presented SeParatelY. BY examining the mortality differentials between sexes, we hope some of the environmental risks can be identified and separated from the genetics of biological causes. Occupational hazards have received little attention in Taiwan and yet, increasing technological adv a n c e ~have often been accompanied llazardous work environby a ment. Estimates are not available on the extent of occupationally related \veil, the spemortality in Taiwan. cific hazards unique to each occupation remain to be studied. In this paper, we compared infant mortality rates by geographic regions in Taiwan and quantified the gender gap in martality. In addition, mortality experience for selected occupational groups will be examined and compared to that of the general population based on the information available through death certificates.
R?Iaterialsand Methods Computerized mortality tapes containing basic demographic data, causes of death, and occupational
217
information for 1981-1986 were acquired from the Department of Health ofTaiwan, Republic ofChina. Population data for the same period were based on the oficial publication of health statistics for Taiwan7. The infant mortality rate was defined as thedeath rate inchildrenless than one year of age. This statistic is often quoted as a useful indicator of the level of health in a community. The infant mortality ratios (IMR) for different geographic areas were calculated by taking the ratios of areaspecific infant mortality ratesand that of the total Taiwan infant mortality rate. If the IMR is greater than 1.OO, the infant mortality from that area is higher than Taiwan by that percentage of the IMR exceeding one. Conversely, an IMK lower than 1.00 indicates infant mortality lower than the average for Taiwan. In this paper the gender gap in mortality was expressed by the ageadjusted mortality ratio for males using the female standard, i.e. male/female standardized mortality ratio (SMR). The SMR was computed as the ratio of the number of observed deaths in males divided by the number of deaths which would have been expected based on the age-specific mortality rates for females*. The expected number of deaths is derived from summing the products of the female mortality rates for each fiveyear age group and the corresponding male population. Significant tests for these SMRs were based on the assumption that the observed number of d e a t h s follows a Poisson distribution'. A two-sided test of significance was used. The causes of death were selected and grouped based on the Ninth Kevision of the International Classification of Diseases. Analysis of occupational risks was based on an evaluation of the proportionate mortality ratio (PMR) of each selected occupation. The PMR is the ratio of the number of observed deaths from a particular cause in a particular occupational group to the expected number derived from age-specific proportions of dcath attributable to that cause for total Taiwan". Statistical 218
significance of a PMK was determined by a summary chi-square test with one degree of freedom". The PMR was chosen instead of SMR because denominators, i.e. population of each occupational category, were not available. Monson's programt2 was modified and age-sex-causespecific mortality proportions for the USA were replaced with those for Taiwan, 1981-1986, to calculate the PMRs. Occupationswithasignificant number of deaths in males were selected for presentation. In interpreting the PMK results, we assumed that theoverall mortality rate for that particular occupation was similar to t h e total Taiwanese mortality ratel3*I4.
Results Infant Mortality Infant mortality for Taiwanasawhole for the years 1981-1986 is shown in Table 1. The average annual infant mortality was 7.42 per 1,000. During the six-year period, a 29% improvement was noted; a rate much faster than the improvement for general mortality7. The ranking of IMR among different cities and counties for 1986 in Taiwan is depicted in Table 2. The highest infant mortality was found among aborigines (IMR = 2.13, which was three times higher than the lowest, Taipei City (IMR = 0.65). The aborigines' IMR was followed by those for Penghu (IMR = 1.61), Taitung (IMR = 1.41), C h i y i ( I M R = 1.37), a n d I l a n (IMR = 1.36). The lower IMRs were Tablc 1. Infant mortality rate* (IhlH) for total Taiwan, 1981-1986
Year
IMK
1981 1982 1983 1984 1985 1986
8.86 8.08 7.64 6.86 6.78 6.29
*Per 1000live births
Source: Department of IIealth, Health Statistics: 2, 1981-1986, Kepublic of China.
noted forTaipeicounty(1MR = 0.78), Taichung City (IMK = 0.82), and Keelung(1MR = 0.92).
Gender Gap in Mortality Females had favorablelife expectancy throughout their lifetimeas compared to males. An advantage of nearly five years was noted for females in 1983. This is reflected by the 5 1% increase of male mortality when compared to females(Tab1e 3). The largest increase was in the middle-age group (ages 15-64 years) where 81% excess of male mortality was seen. The excess ofoverall cancer mortality in males was quite evident with a 54% (SMR= 1.54) increase for all agegroups combined. Inaddition, the mortality ratio increaseswith increasingage, withSMRsof 1.33, 1.47, and 1.68 for the three age groups, respectively. The majority of SMRs for specific major cancer sites were in the ranges between 2 and 3, i.e. cancers for males in major organs were two to three times higher than in females. These included cancer of the nasopharynx (SMK = 2.47), stomach (SMR = 2.04), liver (SMK = 3.12), lung (SMR = 2.09), and Hodgkin's (SMR = 2.32). Two cancer sites, however, were far above the range; cancer of the esophagus (SMK = 5.26) and cancerofthelarynx(SMR = 5.54). Interestingly, these two cancers share common risk factors of alcohol consumption and cigarette smoking as the potential etiology. Cancer of the thyroid gland was the only one that m a l e s d i d not h a v e i n excess (SMR = 0.44). Cancers for which males showed mild elevation were c o l o n ( S M R = 1.06), r e c t u m (SMR = 1.27), brain (SMK = 1.33), leukemia (SMR = 1.60), pancreas (SMR = 1.65), kidney (SMR = 1.33), and bladder (SMR = 1.85). Because genital cancerscould not becompared directly and females had a much larger number of such cancers, the gender gap in mortality for total cancer, which included genital cancer, made the male/female differential less striking (SMR = 1.54). There were only 794 cases of male genital cancers (i.e. prostate, tcsticular, and penile) but 8,25 I cases of female genital cancers (i.e. cervical, ovarian, and breast)
Asia-Pacific Journal of Public Health 1992/1993 Vol. 6 No. 4 Table 2. Ranking order of Infant hlortality Ratio (IhIH) by geographic areas in Taiwan, 1981-1986 Kank
Geographic Areas
1.
Aborigines Penghu County Taitung County Chiayi County Ilan County Hsinchu County Hwalien County Hakka Miaoli County Black Foot Disease Area Taoyuan County Tainan County Kaohsiung County Taichung County Pingtung County Yunlin County Chiayi City Nantou County Changwa County Kaohsiung City Hsinchu City Tainan City Kcelung City Taichung City Taipei County Taipei City
2. 3. 4. 5.
6. 7. 8. 9. 10. 11.
12. 13. 14. 15.
16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.
Total with a crude female/male ratio of approximately tenfold. Males had a 25% higher mortality for diseases of the cardiovascular system. Such an excess was more
Observed Deaths 453 I29 855 732 550
489 375 902 676 140 1157 978 1028 1222 855 839 210
IMR 2.15
1.61 1.41
1.37 1.36 1.33 1.30 1.26 1.25 1.15
1.15 1.14 1.12
I207 978 234 488 25 1 435 1856 1140
1.12 1.10 1.09 1.05 1.02 0.98 0.94 0.94 0.94 0.92 0.82 0.78 0.65
16,656
1.oo
511
marked in ischemic heart disease (SMR = 1.58) than in cerebrovascular disease (SMR = 1.22), particularly in the middle-age group (SMR = 2.00). On the contrary, rheumatic heart
disease afflicted more men than women. Among males, there was a 24% deficit. Male excesses in the respiratory system diseases (SMR = 1.61) was most marked for pneumoconiosis (SMR = 5.41) and emphysema (SMR = 2.77). Pneumoconiosis among males in the 15-64 age group was as much as nine times higher than their female counterparts, a clear implication of occupational hazards. Among all the organ systems examined, the digestive system had the largest disparity of mortality rates between sexes, with that for males being three times higher. Approximately one-halfofthese digestive system diseases were from cirrhosis of the liver which showed a wide gender gap (SMK = 2.96). Peptic ulcers and gastrointestinal bleeding in men also had a twofold increased mortality (SMR = 2.16). Another major discrepancy in mortality between the sexes was for accidents (SMK = 2.88). The gap was widest in the 15-64 age group with an SMR of 3.62. The gap for suicide was relatively smaller (SMR = 1.41) in contrast to the “unintentional injuries” or all accidents (SMR = 2.88), being only one-half of the latter. Males also had a much higher mortality rate for infectious disease than females (SMR= 2.18), particularly for tuberculosis (SMR = 2.98). 0bviously;such a huge difference of nearly threefold between the sexes in infectious disease could not solely be explained on the basis of differences
Table 3. Scx differentials: male/femalc standardized mortality ratio (ShIR) Taiwan, 1981-1986 Age Group Causes ofDeath (ICD-9)
0-14
15-64
All Causes Infectious and Parasitic (001-1 39) Tuberculosis (010-01 8) All Cancer (140-208) Ca. Oral Cavity( 140-149) Ca. Nasopharynx (147) Ca. DigestiveOrgans(150-159) Ca. Esophagus (1 50) Ca. Stomach (1 5 1) Ca. Colon (1 53) Ca. Rectum ( 1 54)
1.29* 1.19* 1.40* 1.33* I .89
1.81* 2.26* 2.69* 1.47* 2.97* 2.48* 2.39* 6.67* 1.84* 1.02 1.15*
-
2.20*
-
0.94 1.70
2
65
Total
1.30*
1SI*
2.52* 3.29* 1.68* 2.64* 2.46* 2.01* 4.35* 2.26*
2.18* 2.98* 1.54* 2.87* 2.47* 2.22* 6.26* 2.04* 1.06* 1.27*
1.09*
1.43*
219
Tablc 3. (Conrinued)
Causes of Death (ICD-9)
0-14
15-64
165
Total
Ca. Liver and Bile duct (1 55-1 56) Ca. Pancreas (1 57) Ca. Respiratory System ( 1 60-1 65) Ca. Larynx(l61) Ca. Lung (1 62) Ca. Bone ( I 70) Ca. Skin(172-173) Ca. Bladder ( I 88) Ca. Kidney (1 89) Ca. Eye (1 90) Ca. Brain-Nervous System (1 9 1- 192) Ca. Thyroid (1 93) Ca. Ill-defined (195-199) Lymphosacoma & Reticulosarcoma (200) Hodgkins Disease (201) Leukemia (204-208) Myeloid Leukemia (205) Multiple Myeloma and Other (202,203) All Lymphatic Tissue (200-208) Benign, Uncertain Nature (210-239) Brain Tumor( 191-192,225) Ca. of Uncertain Behavior (235-239) Endocrine Diseases (240-279) Diabctes (250) Anemia (280-289) Mental Disorder (290-3 19) Nervous System Disease (320-389) Circulatory System Diseases (390-459) Chronic Rheumatic Heart (393-398) Hypertensive Disease (40 1-405) Ischemic Heart (410-414) Cerebrovascular diseasc (430-438) Respiratory Systtm Disease (460-5 19) Pneumonia (480-489) Emphysema (492) Asthma (493) Pneumoconiosis (500-508) Digestive System Disease (520-579) Peptic Ulcer (531-533) All Liver Disease ( 1 55,570-573) Cirrhosis ofLiver (571) PepticUlcer& GI Bleeding(531-533,578) Kidney Diseases (580-608) Chronic Glomerulonephritis (582) Skin Diseases (680-709) Musculo-skeletal Disorder (7 10-739) Congenital Anomalies (740-759) Congenital Heart Disease (745,746) Symptoms, Signs and Ill-defined Condition (780-799) All External Causes (800-999) All Accidents (800-949)
2.54* 0.3 1 1.06
3.65* 1.68* 1.99* 6.08* 1.90* 1.1 I* 1.74* 1.57* 1 ;28* I .oo 1.33* 0.46* 1.07 1.22* 2.09* 1.53*
2.3 1 * 1.61* 2.41* 5.16* 2.36* 1.20* 1.25* 2.07* 1.41* 1.17 I .29* 0.4 1* 1.41* 1.28 3.68*
3.12* 1.65* 2.16* 5.54* 2.09*
1.25*
1.52* 1.44* 1.65* 1.38* 1.25* 1.37* 0.66* 0.63* 0.98 I .74* I .29* 1.14* 0.8 1 * 1.1 I * 1.40* 1.1 I * 1.66* I .44* 2.76* 1.76* 4.76* 2.44* 1.94* 2.07* 1.87* I .90* I .24* 0.80 1.02 0.7 1* 0.42* 0.5 1 0.98 1.86* I .98*
220
-
0.66 I.42* 1.17 0.94 1.21 0.78 1.42*
-
0.84 1.30 2.22 1.55* 1.20 1.26* 1.26* 1.12 1.41* 1.12 0.79 1.50 1.33* 0.72 l.l8* 1.27* 0.69
-
0.95 1.41* 1.13* 1.10*
1.25 1.23 1.02 1.47* 0.95 1.78* 1.14 I .oo 1.13 0.95 0.35* 0.40* 1.09* 1.07* 1.18* I .60* 1.61*
1.29* 1.36* 1.53* 1.30* 1.54* 0.76* 0.73* 0.98 3.43* 1.44* 1.46* 0.71* I .42* 2.00* I .40* 1.79* I .69* 2.86* 1.62* 9.06* 3.68* 2.83* 3.80* 3.71* 2.93* 0.97 0.77* 0.50* 0.58*
1.03 0.95 1.94* 2.99* 3.62*
1.80*
1.15*
I .44* I .85* 1.33* 0.94 1.33* 0.44* 1.16* 1.24* 2.32* 1.60* 1.27* 1.30* 1.39* 1.45* 1.30* I .44* 0.70* 0.67* 1.03 2.49* 1.30* 1.25* 0.76* 1.19* 1.58* 1.22* 1.61* 1.39* 2.77* 1.71* 5.41* 3.04* 2.17* 3.04* 2.96* 2. I6* 1.10*
0.79* 0.7 1* 0.66* I .09* 1.06* 1.13* 2.55* 2.88*
Asia-Pacific Journal of Public Health 199211993 Vol. 6 No. 4
Table 3. (Continued)
Causes of Death (ICD-9)
0-14
15-64
2
65
Total
Motor Vehicle Accidents (8 10-829) Non-Motor Vehicle Accidents (850-929) Pesticide Poisoning (863) Fall (880-888) Drowning (9 10-9 15) Other Accidents (9 16-928) Suicide (950-959)
1.27* 1.79* I .22 1.67* 2.05* 1.36*
3.67* 3.56* 1.78* 3.41* 3.63* 5.67* I .40*
2.51* 1.63* 1.56* 1.29* 1.94* 1.86* I .48*
3.1 I* 2.65* 1.73* 2.37* 2.62* 3.85* 1.41*
1.10
*P c 0.05
in biological susceptibility. While most causesofdeath fornialesshowed an excess, a handful ofnon-cancerous conditions were in the opposite direction. The most notable ones were diabetes (SMK = 0.67), glomerulonephritis (SMR = 0.79), and musculoskeletal disorder (SMR = 0.66).
Occupational Risk Table 4 displays the PMR results for selected occupations using the total
for Taiwan as the comparison. Occupational groups included in the study are fishermen, peasants, soldiers, students, apprentices, and construction workers. Nine major causes of death were selected and, for each cause, two t i m e periods ( 1 9 8 1 - 1 9 8 3 a n d 1984-1986) were separately presented for comparison along with the combined time period (I98 1-1986). The selected occupations were those that had large numbers of
deaths. In addition, these were more traditional jobs that were not subclassified. Thenunibersofdeathsin many other industrial jobs, when subclassified, were too small to be meaningful. It should be recognized that these occupations were entered onto death certificates usually based on the last job before death. If job changes occurred frequently, the occupational analysis based on thedeath certificate was problematic. Another limitation
Table 4. Proportionatc mortality ratios (PAIR) for selectcd occupations Taiwan, 1981-1986
Cause of deaths (ICD-9) All Causes (001-998) All Cancer (140-208) Esophagus ( I 50)
Stomach (151) Liver (1 55) Lung ( I 62) Tuberculosis (010-018) Accidents (800-949) Motor Vehicle (8 10-929) Non-Motor Vehicle Suicide (950-959) All Causes (001-998) All Cancer ( 1 40-208) Esophagus ( 1 50) Stomach ( 1 5 1) Liver (1 55) Lung ( 1 62) Tuberculosis (010-018) Accidents (800-949) Motor Vehicle (810-929) Non-Motor Vehicle Suicide (950-959)
I98 1-1 983 Observed deaths PMR
Fishermen 2867 712 45 125 232 99 91 515
I68 347 55
Peasants 32300 6052 279 925 1712 948 1371 5294 3025 2269 1 I29
1984- I 986 Observed deaths PMR
I .oo 1.19* 1.64* 1.58* 1.35* 0.94 0.95 1.12* 0.68* 1.63* 0.66*
3100 78 1 45 99 243 138 64 531 I86 345 73
I .oo 0.93* 0.90 1.03 0.96 0.80* 1.25* 1.08* 1.14* I .01
35759 6822 306 1015 181 1 1232 I140 5501 3080 242 1
1.oo 0.98 0.89* 1.02 0.98 0.95 0.92* 1.18* I .23*
1.27*
1110
1.27*
1
.oo
1.24* 1.53* 1.17 1.35* 1.23* 0.62* 1.12* 0.73* 1.57* 0.84
1.12*
198 1-1986 Observed deaths 5976 1493 90 224 275 237
I’MR 1 .oo
1046 354 692 128
1.21* 1.58* 1.37* 1.35* 1.09 0.78* 1.12* 0.70* 1.60* 0.75*
68059 12874 585 1940 3533 2180 251 1 I0795 6105 4690 2230
0.96* 0.89* 1.02 0.97 0.88* 1.07* 1.13* 1.18* 1.06* I .27*
155
1
.oo
22 1
Table 4. (Conrinued) Cause of deaths
(ICD-9) All Causes (001-998) All Cancer (1 40-208) Esophagus ( I 50) Stomach(l51) Liver (1 55) Lung (1 62) Tubcrculosis (010-01 8) Accidents (800-949) Motor Vehicle (810-929) Non-Motor Vehicle Suicide (950-959) All Causcs (001-998) All Cancer (140-208) Esophagus (1 50) Stomach ( 1 5 I ) Liver ( 1 55) Lung (1 62) Tuberculosis (010-018) Accidents (800-949) MotorVehiclc(810-929) Non-Motor Vehicle Suicide (950-959) All Causcs (001-998) All Cancer (140-208) Esophagus (1 50) Stomach (1 5 I ) Liver ( 1 55) Lung ( 1 62) Tuberculosis(O10-018) Accidents (800-949) Motor Vehicle (810-929) Non-Motor Vehicle Suicide (950-959)
All Causcs (001-998) All Cancer (140-208) Esophagus ( 1 50) Stomach ( I 5 1) Liver (1 55) Lung (1 62) Tuberculosis (010-0 18) Accidcnts (800-949) Motor Vehicle (8 10-929) Non-Motor Vehicle Suicide (950-959)
*P < 0.05 222
1981-1 983 Obscrvcd deaths
1984-1986 PMR
Soldicrs 2450 1.oo 365 I .02 12 1.02 46 I .26 105 1.oo 58 1.21 17 0.40* I006 0.94 438 0.72* 568 I .23* 223 1.41* Students 4000 I .oo 418 1.08 0 0.00 7 1.99 81 1.18 3 0.7 1 12 0.71 249 1 I .04 975 0.94 1516 1.12* 94 0.72* Apprentices 4490 1.oo 501 0.64* 24 0.87 52 0.63* 161 0.65* 71 0.63* 72 0.70* 2127 1.48* 1293 1.60* 834 1.33* 275 1.27* Construction Workers 1560 1.oo 348 1.09 25 1.94* 40 I .07 111 1.12 53 1.04 43 0.95 375 1.07 209 1.09 166 1.05 42 0.71*
198 1-1986
Observed deaths
PMR
Observed deaths
PMR
2095 287 8 30 75 38
I .oo 1.13 1.01 1.18 1.10
4635 652 20 76 180 96 32 1949 83 1 1109 423
I .oo 1.06 1.02 1.23 1.04 1.18 0.44* 0.95 0.71* 1.27* 1.41*
7664 823 0 I1 152 6 24 4720 1877 2843 210
1.oo 1.1 1
0.83*
12520 1729 79 208 498 286 255 4827 2884 1943 626
0.75* 0.87 0.78* 0.71* 0.80* 0.77* 1.43* 1.54* 1.30* 1.19*
1.15
934 393 54 1 200
0.50* 0.96 0.70* 1.31* 1.40*
3664 405 0 4 71 3 12 2229 902 1327 116
1.14 0.00 I .20 1.13 0.77 0.78 1.02 0.95 1.09* 0.95
8030 1228 55 156 337 215 183 2700 1591 1109 35 1
0.81* 0.87 0.84* 0.75* 0.87* 0.8 I * I .40* I .49* 1.29* I.I4*
15
1560 342 14 39 117 59 44 362 207 155 59
1
.oo
1.oo
1
.oo
1.07 1.06 1.01 1.18 1.14 0.94 1.13* 1.19* 1.06 1.05
3120 690 39 79 228 112 87 737 416 32 1 101
0.00 1.61 1.16 0.74 0.74 1.03
0.94 1.12*
1 .oo
1
.oo
1.08 I .49* I .04 1.15
1.09 0.94 1.10* 1.14* 1.05 0.87
Asia-Pacific Journal of Public Health 1992/1993 Vol. 6 No. 4 that should be noted is that not all death certificates had occupational information. However, there was little reason todoubt the representativeness of these deaths within the occupational population from which they were drawn, given the large samples of selected occupations for this study. The occupational analysis was not conducted for females because the numbers in these occupations were not adequate to draw meaningful conclusions.
Fishermen (Total number of deaths = 5,967) Based on the PMR analysis, there was a statistically increased overall cancer mortality(PMR = 1.2 1)for fishermen in Taiwan, and the trend was increasing. Several majorcancer sites showed statistically increased PMRs, including stomach ( P M R = 1.37), esophagus (PMR = 1.58), and liver (PMR = 1.35). Accidental deaths were also increased (PMR = 1.12) due mainly to non-motor vehicle accidents such as drowning. Deaths from motor vehicle accidents (PMR = 0.70) were significantly below the national average. Peasants (Total number of deaths = 68,059) The peasants, the largest of the occupational groups analyzed, had significantly increased mortality for motor vehicle accidents (PMR = 1.18) and suicide (PMR = 1.27). The proportion of death from all accidents increased during the period. Tuberculosis had a slight increase (PMR = 1.07) compared with the total Taiwan population although it had been declining. Cancersofthelung(PMR = 0.88) and esophagus (PMK = 0.89) were statistically lower. Soldiers (Total number of deaths = 4,635) The slight elevation of overall cancer mortality (PMR = 1.06) among soldiers was primarily attributed to the increase in stomach (PMK = 1.23) and lung (PMR = 1.18) cancers. A significant increase was seen in suicide (PMR = 1.41) throughout the two time periods. Deaths from motor ve-
hicleaccidentswerein deficit but nonmotor vehicle accidental deaths (PMR = 1.32) were in excess. Tuberculosis among soldiers was significantly lower than the general population (PMR = 0.44), i.e. less than onehalfofthe expected.
Students (Total number of deaths = 7,664) Because oftheir young age, the majority of deaths were from accidents, which had aslightly increased mortality (PMR = 1.03). The PMR for nonmotor vehicle accidents increased 12% (PMR = 1.12). Suicide was in deficit (PMR = 0.83). The relative number of cancer deaths in students was small but had an 11% increased PMR. It is noteworthy that cancer of the stomach and liver increased as much as 61% and 16% respectively, although their numbers were small.
Apprentices (Total number of deaths = 12,520) Apprentices had significantly increased accidental deaths (PMR = 1.43) f o r both m o t o r vehicle (PMR = 1.54) and non-motor vehicle accidents (PMK = 1.30). Suicide (PMR = 1.19) was also significantly higher than for the general population. As for cancer, apprentices had approximately a 25% deficit across the board.
Construction Workers(Total number of deaths = 3,120) The total number of deaths among construction workers was the smallest among the selected occupational groups. Slightly elevated mortality rates were seen for all cancers (PMR = 1.08), liver cancer (PMR = 1 - 1 3 ,and lung cancer (PMK = 1.09). Cancer of the esophagus was statistically increased (PMR = 1.49) which was primarily due to the 1981-1983 time period. Accidental deathsamong construction workers were significantly higherthan forthegeneral population (PMR = 1.10). Suicide was lower (PMR = 0.87) for the total sixyear study time period, but the PMR increased substantially from 1981-1983 to 1984-1986.
Discussion Infant mortality represents the largest number of deaths in a single age group. This could serve as an index of quality and availability of medical care in the population. The high infant mortality rate on the east coast of Taiwan supported the impression about inadequate medical care among the residents of these areas. This is over and above the lifestyle factors that contributed to much of the increased mortality among adult residents in this region. In general, the infant mortality correlated well with overall mortality for different geographic areas3, suggesting that there are many common risk factors affecting all age groups in the same areas. In otherwords, higher infant mortality was accompanied by higher total mortality and a lower infant mortalitywithlowertotalmortality. However, several notable exceptions were seen. Penghu had a general mortality the same as the average Taiwan mortality, but had an infant mortality 61% higher. Similar patterns were found amongareas where Hakka were the majority of residents. These areas included Taoyuan, Hsinchu county, and Miaoli. The SMRs for total mortality were less than the Taiwan average, 0.93, 0.98, and 0.99, respectively. However, the corresponding IMRs were above the average, 1.15,1.33,and 1.25,respectively. Such a divergence might suggest an inadequacyof preventive and critical care for infants as compared to care for adults and the elderly. Special efforts to improve the prenatal and postnatal care in these geographic areas are needed. Under-reporting of infant mortality in Taiwan has been noted to be as high as 46-96%”. The true infant mortality in Taiwan was estimated to be 11-14 per 1,000‘6, such underreporting must have occurred across all cities and counties so that it should not substantially affect the ranking order presented. I t is likely, however, that the higher the infant mortality, the greater the under-reporting, particularly in the case of the aborigines and rural counties. Thus it cannot be overemphasized that, for improving infant mortality statistics, a two-
223
pronged approach is necessary, i.e. improve infant survival by providing betterhealth carewhileimprovingthe completeness of birth registration regardless ofthe vital status. The reason for the universally observed high male sex mortality ratio remains a mystery and presents a challenge. It is alarming to note that the largest male/female mortality differential in Taiwanwas in the middleage group (ages 15-64 years) with the SMR of 1.8 1 where for every five female deaths there were nine males deaths. This is most disturbing because this age group represents the most productive years in a person’s lifetime. Those years were disproportionately lost by males. Many of the gender gaps observed for different causes could be partially explained by lifestyle risk factors which were more prevalent among males. Similarly, occupational hazards were also more associated witha male-dominated work environment. For example, the twofold increase of lung cancer among males wasprobablyrelated to their 15 times greater cigarette smoking rateI7, and could also be related to their occupational exposures or a combination of b ~ t h ’ ~ .It’ ~can . be hypothesized that the larger the gender gap the greater the chance of an environmental etiology. In this regard, the size of the gendergap could be ranked as follows: cancer of the larynx (SMR = 5.54), pneumoconiosis (SMR = 5.41), cancer of the esophagus (SMR = 5.26), homicide (SMR = 3.62), motor vehicle accidents (SMR = 3. I l), all liver diseases (SMR = 3.04), tuberculosis (SMK = 2.98), cancer of the oral cavity (SMR = 2.97), and emphysema (SMR = 2.77). All of these have been shown to be associated with known environmental The presence ofthe largegender gap made the suspected environmental cause more plausible. Of all the cancers, the largest differentials in sex mortality ratio were cancers of the larynx and esophagus, both with more than fivefold increase in males. These two cancer site have been postulated as being associated with alcohol drinking in addition to cigarette smoking21*22.Men smoked
224
and drank more than women in terms of frequency, concentration of alcohol consumed, and v o l ~ m e ’ Judg~. ing from the size of the gender gap, these two cancers in men have reached an epidemic proportion in Taiwan. The etiological factors for these two cancers were not well studied inTaiwanand wereelusiveat best, other than the established association with cigarette smoking (two to six times higher risk for smokers than non-smokers). The alcohol exerted an independent risk in addition to a synergistic effect with smokingwhich has been reported22. The much-increased mortality ratio for these two cancers sitewhen compared with that for lung cancer which was primarily related to smokingattested to the suggested role of alcohol consumption in their etiology in men. The next two increased sex mortality ratios with largest male excesses were homicide(SMR = 3.62)and motor vehicle accidents (SMR = 3.1 l), both of which were related to increased lifestyle risks in men. Clearly, these two causes of death were exclusively environmental in etiology. Tuberculosis (SMR = 2.98) and emphysema (SMR = 1.7 1) were also increased in males, reinforcing the hazards of certain lifestyles and personal exposure in a crowded environment. Smoking and air pollution aggravated the disparity between the sexes while the role of biological differences was generally not yet recognized as important. Another large differential was seen in cancer of the oral cavity (SMR = 2.87), includingcancerofthe nasopharynx (SMR = 2.47). In view of the oral cavity’s anatomical proximity to the larynx and esophagus, smoking and alcohol could have played an important role in their etiology23.Apparently, such a hypothesis is provocative because these two factors alone are far from adequate in explaining the extraordinary rates of these cancers in the Chinese population. Other etiological agents such as diet may play a role. It has been widely recognized that, with rapid industrialization, occupational hazards would play an increasingrole in developingcancerand
otherconditions. A number ofstudies had reported adverse health effects based on proportionate mortality analyses suggesting possible occupational risks and exposure^^^-^^. Since these PMR analyses were for screening and were preliminary in nature, the findings should be viewed as hypothesis generating. The limitations of PMR statistics should be fully recognized when collection of death certificates is incomplete. When the underlyingoverall mortalityislowforan occupational group, the values of PMR could be Furthermore, the completeness and accuracy of the occupational entries on death certificates in Taiwan are far from desirable. The inherent weaknesses of a death certificate study need to be further evaluated by other niethodsof research. Of the occupations analyzed, the increased risk in overall cancer for fishermen, especially in the case of gastrointestinal cancer, was most noteworthy. Such findings among Chinese fishermen in Hong Kongand Singapore had been repeatedly r e p o r t ~ d ~ ’ Further * ~ ~ . studies regarding their diet, lifestyle, and other risk factors may be worthwhile. It is not surprising to note that death for fishermen from drowning was increased while death from motor vehicle accidents were decreased when compared to the general population. High motor vehicle accidents and suicide mortality amongpeasants implied that they were no longer immune to the side effectsofmechanization or work-related stress even in the rural areas of Taiwan. Relatively cleaner air might have contributed to their low lung cancer mortality. Smoking is highly prevalent among men in Taiwan, but more so among soldiers. There was a long-held tradition in the military services of supplying free cigarettes to soldiers as a fringe benefit. The effect ofthis practice has started to surface with the resulting increase in lung cancer mortality. Soldiers also had a high suicide rate, a not unexpected finding to account for their depressed feelings from limitedcareeropportunitiesand restricted individual freedom. However, the good discipline and the
Asia-Pacific Journal of Public Health 1992/1993 Vol. 6 No. 4 bet ter-t han-average preventive health services among soldiers h a d m a d e motor vehicle accidents a n d tuberculosis m u c h less likely. At present, it is unclear why stomach cancer was high among students. It is important to note that t h e suicide r a t e was not increased despite high pressure to advance to a higher level of education. T h a t apprentices h a d high m o t o r vehicle accidents was understandable since they were often requested t o go on t h e road for errands. T h r e c distinctly different types of statistics were used based on the existing mortality data to assess the role o f e n v i r o n m e n t a l factors in causing mortality variations in Taiwan. Each set of analysis yielded insightful results of unique epidemiological significance that h a d n o t previouslybeen reported. This paper illustrated the usefulness of systematic analyses of routinely collected data. F i n d i n g s from this s t u d y are useful in setting priorities for health a n d safety problems and directing efforts s u c h as health education programs a n d other disease prevention strategies.
References TsaiSP,WenCP. Mortalitytrendsin a rapidly developing economy in Taiwan. Part I: Comparison with the USA and Japan,’1976-1983. Asia Pac J Public Health 1989;3:41-50. Tsai SP, Wen CP, Tsai S E Mortality trends in a rapidly developing economy in Taiwan. Part 11: Life expectancy and premature mortality. Asia Pac J Public Health 1991;5:49-53. Wen CP, Tsai SF, Guo JP, Tsai SI’. Mortality analysis in Taiwan - Geographicdifference. In Wen CP, Chen CJ (Editors): I989 IBMS Year Book by Epidemiology and Public Health Group, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, Republic of China, pp. 53-100,1989.
4. Antonovsky A, Bernstein J. Social class and infant mortality. SOCSci Med 1977;11:453-470. 5. Madigan FC. Are sex mortality differentials biological caused? Milbank Mem Q 1957;35:202-33. 6. Calabress EG. Toxic Susceptibility: Malelfemale Differences. WileyIntersciences, 1986. 7. Department of Health, Executive Yuan. Health Statistics I. General Health Statistics. RepublieofChina, 1981,1986. 8. Tsai SP, Wen CP. Methodological issues of standardized mortality ratio (SMR) in occupational cohort studies. Int J Epidemiol 1986; 15:8-12.
9. Bailar J C 111, Ederer F. Significance factors fortheratioofa Poisson variable to its expectation. Biometrics 1964;20:639-43. 10. Kupper LL, hlcMichael AJ, Symons hlJ, ct al. On the utility of proportional mortality analysis. J Chron Dis 1978;31:15-22. 11. Mantel N, Haenszcl W. Statistical aspects of the analysis of data from retrospective studies of disease. J Natl Cancer Inst 1959;22:719-48. 12. Monson RR. Analysisofrelativesurviva1 and proportional mortality. Computers Biomed Res 1974; 1~325-32. 13. Decoufle P, Thomas TL, Pickle LW. Comparison of the proportionate mortality ratio and standardized mortality ratio risk measures. Am J Epidemiol 1980;l I1:263-9. 14. Wong 0, Decoufle P. Methodological issues involving thestandardized mortality ratio and proportionate mortality ratio in occupational studies. JOccup Med 1982;24:299301. 15. W u SC, Young CL. A study o n the birth registration system. J National Public Health Assoc (K.O.C.) 1986~6:15-27. T. 16. WuSC, Chang C, Hsieh SJ, Liou I Astudyon thepromotingofpopulation registration. Health Statistics, 11. Vital Statistics 1987. Republic of China: Department ofHealth, ExecutiveYuan,p. 521, 1988.
17. Taiwan Provincial Tobacco and Liquor Monopoly Bureau. Tobacco and Liquor Consumption Survey for Taiwan Area, 1986 (in Chinese). Taiwan, Republic of China: Taiwan Provincial Tobacco and Liquor Monopoly Bureau, 1987. 18. Fraumeni FJ, Blot W. Lung and pleura. In: Schottenfeld D, Fraumeni JF, editors, CancerEpidemiology and Prevention. Philadelphia, PA: WB S a u n d e r s C o m p a n y , 198256442. 19. Doll R, Peto R. The Causes of Cancer: Quantitative Estimates of Avoidable Risks of Cancer in the United States Today. NewYork: Oxford University Press, 1981. 20. The National Committee for Injury Prevention and Control. Injury Prevention: Meeting the Challenge. New York, Ny: Oxford University Press, 1989. 21. Wynder EL, Hoffmann D. Tobacco. In: Schottenfeld D, Fraumeni JF, editors, Cancer Epidemiology and Prevention. Philadelphia, PA: WB Saunders Company, 1982:277-92. 22. Tuyns AJ. Alcohol. In: Schottenfeld D, Fraumeni JF,editors,CancerEpidemiology and Prevention. Philadelphia, PA: WB Saunders Company, 1982:293-303. 23. Mahboubi E, Sayed GM. Oral cavity and pharynx. In: Schottenfeld D, Fraumeni JF, editors, Cancer Epidemiology and Prevention. Philadelphia, PA: WB Saunders Company, 1982~583-95. 24. Monson RR, Peter JM, Johnson MN. Proportional mortality among vinyl-chloride workers. Lancet 1974;2:297-398. 25. Milham S. Methods inoccupational mortality studies. J Occup Med 1975;17:581-5. 26. Thomas TL, Waxweiler RJ, MoureEraso R. Mortality patterns among workers in three Texasoil refineries. J Occup hled 1982;24: 135-4 1. 27. Ng TP. Occupational mortality in Hong Kong, 1979-1983. Int J Epidemiol 1988; 17: 105-10. 28. Jeyaratnam J, Lee J, Lce HP, et al. Stomach cancer incidence in a CDhort of fishermen in Singapore. Scand J Work Environ Health 1987;13:524-6.
225
Mortality data of Taiwan for 1981 through 1986 were analyzed using three difierent statistics in order to assess the role of environmental and tifestyle factors in causing mortality variations. Infant mortality rates from different geographic regions generally correlated well with overall mortality from all ages, suggesting that there are many common risk factors affecting the entire age range of the population. The mortality rates of tobacco- and alcohol-related causes of death and cancers were much higher in males than females. A numberofcancer sites, including the lung, the Liver, the stomach, and the oasopharynx, showed more than twofold excesses in males. In contrast, females had a tenfold excessof genital cancer and a 33%higher rate of diabetes. With rapid industrialization, occupational hazards played an increasing role in the development of cancer and other causes of death. During the study period, fishermen showed increased risk for cancers of the stomach, the esophagus, and the liver, while construction workers had an increased risk for cancer of the esophagus. Peasants and soldiers bad an elevated suicide mortality. Among apprentices, fatal injuries were high. Findings h m this study are useful in setting priorities for health and safety programs and directing efforts such as health education programs and other preventive strategies against disease. Asia Pac J Public Health 1992A993;6(4):217-25.
Keywords: Cancer, gender gap, infant mortality, occupational hazards.
Address for Reprints: Dr chi-Pang Wen Institute of Biomcdid Scicnms,Academia
Sinica, Taipei,Taiwan,ROC.
Mortality Experience in a Rapidly Developing Economy in Taiwan: Infant Mortality, Gender Gap, and Occupational Risks Chi-Pang Wen, MD, P h D Shu-Fang Tsai, M P H Shan-Pou Tsai, PhD Institute of Biomedical Sciences Academia Sinica Taipei, Taiwan ROC Introduction Oneofthe most important featuresof epidemiological research is to study variations in disease distribution. We can unmask the causative factors and explore preventive measures by identifying environmental characteristics shared by not only those with high frequency of disease but also those with low prevalence of disease. In reviewing the mortality data of Taiwan, there are three areas of mortalityvariation that havenot been addressed in previous papers'-3 but are believed to contribute significantlyto the understanding ofthe environmental factors on mortality in Taiwan. They are Variations in infant mortality, differences in the male/female gender gap, and risks from OCCUpational hazards. a Infant has great deal Of attention because it Can be used as an index of health care quality- It is a good indicator of the socioeconomic development ofa geographicarea' aswellasa Yardstick for evaluating the degree of Success in Several areas such as prenatal Care, quality of child health services, and nutritional adequacy of the newborn. Mortality rates for males are quite different from those for females. The gender gap or sex differentials in mortality have long been recognized
in epidemiological literatures*6.Since malesand femalesare biologicallydistinct entities and mortality rates between these populations are widely varied, data are usually Presented SeParatelY. BY examining the mortality differentials between sexes, we hope some of the environmental risks can be identified and separated from the genetics of biological causes. Occupational hazards have received little attention in Taiwan and yet, increasing technological adv a n c e ~have often been accompanied llazardous work environby a ment. Estimates are not available on the extent of occupationally related \veil, the spemortality in Taiwan. cific hazards unique to each occupation remain to be studied. In this paper, we compared infant mortality rates by geographic regions in Taiwan and quantified the gender gap in martality. In addition, mortality experience for selected occupational groups will be examined and compared to that of the general population based on the information available through death certificates.
R?Iaterialsand Methods Computerized mortality tapes containing basic demographic data, causes of death, and occupational
217
information for 1981-1986 were acquired from the Department of Health ofTaiwan, Republic ofChina. Population data for the same period were based on the oficial publication of health statistics for Taiwan7. The infant mortality rate was defined as thedeath rate inchildrenless than one year of age. This statistic is often quoted as a useful indicator of the level of health in a community. The infant mortality ratios (IMR) for different geographic areas were calculated by taking the ratios of areaspecific infant mortality ratesand that of the total Taiwan infant mortality rate. If the IMR is greater than 1.OO, the infant mortality from that area is higher than Taiwan by that percentage of the IMR exceeding one. Conversely, an IMK lower than 1.00 indicates infant mortality lower than the average for Taiwan. In this paper the gender gap in mortality was expressed by the ageadjusted mortality ratio for males using the female standard, i.e. male/female standardized mortality ratio (SMR). The SMR was computed as the ratio of the number of observed deaths in males divided by the number of deaths which would have been expected based on the age-specific mortality rates for females*. The expected number of deaths is derived from summing the products of the female mortality rates for each fiveyear age group and the corresponding male population. Significant tests for these SMRs were based on the assumption that the observed number of d e a t h s follows a Poisson distribution'. A two-sided test of significance was used. The causes of death were selected and grouped based on the Ninth Kevision of the International Classification of Diseases. Analysis of occupational risks was based on an evaluation of the proportionate mortality ratio (PMR) of each selected occupation. The PMR is the ratio of the number of observed deaths from a particular cause in a particular occupational group to the expected number derived from age-specific proportions of dcath attributable to that cause for total Taiwan". Statistical 218
significance of a PMK was determined by a summary chi-square test with one degree of freedom". The PMR was chosen instead of SMR because denominators, i.e. population of each occupational category, were not available. Monson's programt2 was modified and age-sex-causespecific mortality proportions for the USA were replaced with those for Taiwan, 1981-1986, to calculate the PMRs. Occupationswithasignificant number of deaths in males were selected for presentation. In interpreting the PMK results, we assumed that theoverall mortality rate for that particular occupation was similar to t h e total Taiwanese mortality ratel3*I4.
Results Infant Mortality Infant mortality for Taiwanasawhole for the years 1981-1986 is shown in Table 1. The average annual infant mortality was 7.42 per 1,000. During the six-year period, a 29% improvement was noted; a rate much faster than the improvement for general mortality7. The ranking of IMR among different cities and counties for 1986 in Taiwan is depicted in Table 2. The highest infant mortality was found among aborigines (IMR = 2.13, which was three times higher than the lowest, Taipei City (IMR = 0.65). The aborigines' IMR was followed by those for Penghu (IMR = 1.61), Taitung (IMR = 1.41), C h i y i ( I M R = 1.37), a n d I l a n (IMR = 1.36). The lower IMRs were Tablc 1. Infant mortality rate* (IhlH) for total Taiwan, 1981-1986
Year
IMK
1981 1982 1983 1984 1985 1986
8.86 8.08 7.64 6.86 6.78 6.29
*Per 1000live births
Source: Department of IIealth, Health Statistics: 2, 1981-1986, Kepublic of China.
noted forTaipeicounty(1MR = 0.78), Taichung City (IMK = 0.82), and Keelung(1MR = 0.92).
Gender Gap in Mortality Females had favorablelife expectancy throughout their lifetimeas compared to males. An advantage of nearly five years was noted for females in 1983. This is reflected by the 5 1% increase of male mortality when compared to females(Tab1e 3). The largest increase was in the middle-age group (ages 15-64 years) where 81% excess of male mortality was seen. The excess ofoverall cancer mortality in males was quite evident with a 54% (SMR= 1.54) increase for all agegroups combined. Inaddition, the mortality ratio increaseswith increasingage, withSMRsof 1.33, 1.47, and 1.68 for the three age groups, respectively. The majority of SMRs for specific major cancer sites were in the ranges between 2 and 3, i.e. cancers for males in major organs were two to three times higher than in females. These included cancer of the nasopharynx (SMK = 2.47), stomach (SMR = 2.04), liver (SMK = 3.12), lung (SMR = 2.09), and Hodgkin's (SMR = 2.32). Two cancer sites, however, were far above the range; cancer of the esophagus (SMK = 5.26) and cancerofthelarynx(SMR = 5.54). Interestingly, these two cancers share common risk factors of alcohol consumption and cigarette smoking as the potential etiology. Cancer of the thyroid gland was the only one that m a l e s d i d not h a v e i n excess (SMR = 0.44). Cancers for which males showed mild elevation were c o l o n ( S M R = 1.06), r e c t u m (SMR = 1.27), brain (SMK = 1.33), leukemia (SMR = 1.60), pancreas (SMR = 1.65), kidney (SMR = 1.33), and bladder (SMR = 1.85). Because genital cancerscould not becompared directly and females had a much larger number of such cancers, the gender gap in mortality for total cancer, which included genital cancer, made the male/female differential less striking (SMR = 1.54). There were only 794 cases of male genital cancers (i.e. prostate, tcsticular, and penile) but 8,25 I cases of female genital cancers (i.e. cervical, ovarian, and breast)
Asia-Pacific Journal of Public Health 1992/1993 Vol. 6 No. 4 Table 2. Ranking order of Infant hlortality Ratio (IhIH) by geographic areas in Taiwan, 1981-1986 Kank
Geographic Areas
1.
Aborigines Penghu County Taitung County Chiayi County Ilan County Hsinchu County Hwalien County Hakka Miaoli County Black Foot Disease Area Taoyuan County Tainan County Kaohsiung County Taichung County Pingtung County Yunlin County Chiayi City Nantou County Changwa County Kaohsiung City Hsinchu City Tainan City Kcelung City Taichung City Taipei County Taipei City
2. 3. 4. 5.
6. 7. 8. 9. 10. 11.
12. 13. 14. 15.
16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.
Total with a crude female/male ratio of approximately tenfold. Males had a 25% higher mortality for diseases of the cardiovascular system. Such an excess was more
Observed Deaths 453 I29 855 732 550
489 375 902 676 140 1157 978 1028 1222 855 839 210
IMR 2.15
1.61 1.41
1.37 1.36 1.33 1.30 1.26 1.25 1.15
1.15 1.14 1.12
I207 978 234 488 25 1 435 1856 1140
1.12 1.10 1.09 1.05 1.02 0.98 0.94 0.94 0.94 0.92 0.82 0.78 0.65
16,656
1.oo
511
marked in ischemic heart disease (SMR = 1.58) than in cerebrovascular disease (SMR = 1.22), particularly in the middle-age group (SMR = 2.00). On the contrary, rheumatic heart
disease afflicted more men than women. Among males, there was a 24% deficit. Male excesses in the respiratory system diseases (SMR = 1.61) was most marked for pneumoconiosis (SMR = 5.41) and emphysema (SMR = 2.77). Pneumoconiosis among males in the 15-64 age group was as much as nine times higher than their female counterparts, a clear implication of occupational hazards. Among all the organ systems examined, the digestive system had the largest disparity of mortality rates between sexes, with that for males being three times higher. Approximately one-halfofthese digestive system diseases were from cirrhosis of the liver which showed a wide gender gap (SMK = 2.96). Peptic ulcers and gastrointestinal bleeding in men also had a twofold increased mortality (SMR = 2.16). Another major discrepancy in mortality between the sexes was for accidents (SMK = 2.88). The gap was widest in the 15-64 age group with an SMR of 3.62. The gap for suicide was relatively smaller (SMR = 1.41) in contrast to the “unintentional injuries” or all accidents (SMR = 2.88), being only one-half of the latter. Males also had a much higher mortality rate for infectious disease than females (SMR= 2.18), particularly for tuberculosis (SMR = 2.98). 0bviously;such a huge difference of nearly threefold between the sexes in infectious disease could not solely be explained on the basis of differences
Table 3. Scx differentials: male/femalc standardized mortality ratio (ShIR) Taiwan, 1981-1986 Age Group Causes ofDeath (ICD-9)
0-14
15-64
All Causes Infectious and Parasitic (001-1 39) Tuberculosis (010-01 8) All Cancer (140-208) Ca. Oral Cavity( 140-149) Ca. Nasopharynx (147) Ca. DigestiveOrgans(150-159) Ca. Esophagus (1 50) Ca. Stomach (1 5 1) Ca. Colon (1 53) Ca. Rectum ( 1 54)
1.29* 1.19* 1.40* 1.33* I .89
1.81* 2.26* 2.69* 1.47* 2.97* 2.48* 2.39* 6.67* 1.84* 1.02 1.15*
-
2.20*
-
0.94 1.70
2
65
Total
1.30*
1SI*
2.52* 3.29* 1.68* 2.64* 2.46* 2.01* 4.35* 2.26*
2.18* 2.98* 1.54* 2.87* 2.47* 2.22* 6.26* 2.04* 1.06* 1.27*
1.09*
1.43*
219
Tablc 3. (Conrinued)
Causes of Death (ICD-9)
0-14
15-64
165
Total
Ca. Liver and Bile duct (1 55-1 56) Ca. Pancreas (1 57) Ca. Respiratory System ( 1 60-1 65) Ca. Larynx(l61) Ca. Lung (1 62) Ca. Bone ( I 70) Ca. Skin(172-173) Ca. Bladder ( I 88) Ca. Kidney (1 89) Ca. Eye (1 90) Ca. Brain-Nervous System (1 9 1- 192) Ca. Thyroid (1 93) Ca. Ill-defined (195-199) Lymphosacoma & Reticulosarcoma (200) Hodgkins Disease (201) Leukemia (204-208) Myeloid Leukemia (205) Multiple Myeloma and Other (202,203) All Lymphatic Tissue (200-208) Benign, Uncertain Nature (210-239) Brain Tumor( 191-192,225) Ca. of Uncertain Behavior (235-239) Endocrine Diseases (240-279) Diabctes (250) Anemia (280-289) Mental Disorder (290-3 19) Nervous System Disease (320-389) Circulatory System Diseases (390-459) Chronic Rheumatic Heart (393-398) Hypertensive Disease (40 1-405) Ischemic Heart (410-414) Cerebrovascular diseasc (430-438) Respiratory Systtm Disease (460-5 19) Pneumonia (480-489) Emphysema (492) Asthma (493) Pneumoconiosis (500-508) Digestive System Disease (520-579) Peptic Ulcer (531-533) All Liver Disease ( 1 55,570-573) Cirrhosis ofLiver (571) PepticUlcer& GI Bleeding(531-533,578) Kidney Diseases (580-608) Chronic Glomerulonephritis (582) Skin Diseases (680-709) Musculo-skeletal Disorder (7 10-739) Congenital Anomalies (740-759) Congenital Heart Disease (745,746) Symptoms, Signs and Ill-defined Condition (780-799) All External Causes (800-999) All Accidents (800-949)
2.54* 0.3 1 1.06
3.65* 1.68* 1.99* 6.08* 1.90* 1.1 I* 1.74* 1.57* 1 ;28* I .oo 1.33* 0.46* 1.07 1.22* 2.09* 1.53*
2.3 1 * 1.61* 2.41* 5.16* 2.36* 1.20* 1.25* 2.07* 1.41* 1.17 I .29* 0.4 1* 1.41* 1.28 3.68*
3.12* 1.65* 2.16* 5.54* 2.09*
1.25*
1.52* 1.44* 1.65* 1.38* 1.25* 1.37* 0.66* 0.63* 0.98 I .74* I .29* 1.14* 0.8 1 * 1.1 I * 1.40* 1.1 I * 1.66* I .44* 2.76* 1.76* 4.76* 2.44* 1.94* 2.07* 1.87* I .90* I .24* 0.80 1.02 0.7 1* 0.42* 0.5 1 0.98 1.86* I .98*
220
-
0.66 I.42* 1.17 0.94 1.21 0.78 1.42*
-
0.84 1.30 2.22 1.55* 1.20 1.26* 1.26* 1.12 1.41* 1.12 0.79 1.50 1.33* 0.72 l.l8* 1.27* 0.69
-
0.95 1.41* 1.13* 1.10*
1.25 1.23 1.02 1.47* 0.95 1.78* 1.14 I .oo 1.13 0.95 0.35* 0.40* 1.09* 1.07* 1.18* I .60* 1.61*
1.29* 1.36* 1.53* 1.30* 1.54* 0.76* 0.73* 0.98 3.43* 1.44* 1.46* 0.71* I .42* 2.00* I .40* 1.79* I .69* 2.86* 1.62* 9.06* 3.68* 2.83* 3.80* 3.71* 2.93* 0.97 0.77* 0.50* 0.58*
1.03 0.95 1.94* 2.99* 3.62*
1.80*
1.15*
I .44* I .85* 1.33* 0.94 1.33* 0.44* 1.16* 1.24* 2.32* 1.60* 1.27* 1.30* 1.39* 1.45* 1.30* I .44* 0.70* 0.67* 1.03 2.49* 1.30* 1.25* 0.76* 1.19* 1.58* 1.22* 1.61* 1.39* 2.77* 1.71* 5.41* 3.04* 2.17* 3.04* 2.96* 2. I6* 1.10*
0.79* 0.7 1* 0.66* I .09* 1.06* 1.13* 2.55* 2.88*
Asia-Pacific Journal of Public Health 199211993 Vol. 6 No. 4
Table 3. (Continued)
Causes of Death (ICD-9)
0-14
15-64
2
65
Total
Motor Vehicle Accidents (8 10-829) Non-Motor Vehicle Accidents (850-929) Pesticide Poisoning (863) Fall (880-888) Drowning (9 10-9 15) Other Accidents (9 16-928) Suicide (950-959)
1.27* 1.79* I .22 1.67* 2.05* 1.36*
3.67* 3.56* 1.78* 3.41* 3.63* 5.67* I .40*
2.51* 1.63* 1.56* 1.29* 1.94* 1.86* I .48*
3.1 I* 2.65* 1.73* 2.37* 2.62* 3.85* 1.41*
1.10
*P c 0.05
in biological susceptibility. While most causesofdeath fornialesshowed an excess, a handful ofnon-cancerous conditions were in the opposite direction. The most notable ones were diabetes (SMK = 0.67), glomerulonephritis (SMR = 0.79), and musculoskeletal disorder (SMR = 0.66).
Occupational Risk Table 4 displays the PMR results for selected occupations using the total
for Taiwan as the comparison. Occupational groups included in the study are fishermen, peasants, soldiers, students, apprentices, and construction workers. Nine major causes of death were selected and, for each cause, two t i m e periods ( 1 9 8 1 - 1 9 8 3 a n d 1984-1986) were separately presented for comparison along with the combined time period (I98 1-1986). The selected occupations were those that had large numbers of
deaths. In addition, these were more traditional jobs that were not subclassified. Thenunibersofdeathsin many other industrial jobs, when subclassified, were too small to be meaningful. It should be recognized that these occupations were entered onto death certificates usually based on the last job before death. If job changes occurred frequently, the occupational analysis based on thedeath certificate was problematic. Another limitation
Table 4. Proportionatc mortality ratios (PAIR) for selectcd occupations Taiwan, 1981-1986
Cause of deaths (ICD-9) All Causes (001-998) All Cancer (140-208) Esophagus ( I 50)
Stomach (151) Liver (1 55) Lung ( I 62) Tuberculosis (010-018) Accidents (800-949) Motor Vehicle (8 10-929) Non-Motor Vehicle Suicide (950-959) All Causes (001-998) All Cancer ( 1 40-208) Esophagus ( 1 50) Stomach ( 1 5 1) Liver (1 55) Lung ( 1 62) Tuberculosis (010-018) Accidents (800-949) Motor Vehicle (810-929) Non-Motor Vehicle Suicide (950-959)
I98 1-1 983 Observed deaths PMR
Fishermen 2867 712 45 125 232 99 91 515
I68 347 55
Peasants 32300 6052 279 925 1712 948 1371 5294 3025 2269 1 I29
1984- I 986 Observed deaths PMR
I .oo 1.19* 1.64* 1.58* 1.35* 0.94 0.95 1.12* 0.68* 1.63* 0.66*
3100 78 1 45 99 243 138 64 531 I86 345 73
I .oo 0.93* 0.90 1.03 0.96 0.80* 1.25* 1.08* 1.14* I .01
35759 6822 306 1015 181 1 1232 I140 5501 3080 242 1
1.oo 0.98 0.89* 1.02 0.98 0.95 0.92* 1.18* I .23*
1.27*
1110
1.27*
1
.oo
1.24* 1.53* 1.17 1.35* 1.23* 0.62* 1.12* 0.73* 1.57* 0.84
1.12*
198 1-1986 Observed deaths 5976 1493 90 224 275 237
I’MR 1 .oo
1046 354 692 128
1.21* 1.58* 1.37* 1.35* 1.09 0.78* 1.12* 0.70* 1.60* 0.75*
68059 12874 585 1940 3533 2180 251 1 I0795 6105 4690 2230
0.96* 0.89* 1.02 0.97 0.88* 1.07* 1.13* 1.18* 1.06* I .27*
155
1
.oo
22 1
Table 4. (Conrinued) Cause of deaths
(ICD-9) All Causes (001-998) All Cancer (1 40-208) Esophagus ( I 50) Stomach(l51) Liver (1 55) Lung (1 62) Tubcrculosis (010-01 8) Accidents (800-949) Motor Vehicle (810-929) Non-Motor Vehicle Suicide (950-959) All Causcs (001-998) All Cancer (140-208) Esophagus (1 50) Stomach ( 1 5 I ) Liver ( 1 55) Lung (1 62) Tuberculosis (010-018) Accidents (800-949) MotorVehiclc(810-929) Non-Motor Vehicle Suicide (950-959) All Causcs (001-998) All Cancer (140-208) Esophagus (1 50) Stomach (1 5 I ) Liver ( 1 55) Lung ( 1 62) Tuberculosis(O10-018) Accidents (800-949) Motor Vehicle (810-929) Non-Motor Vehicle Suicide (950-959)
All Causcs (001-998) All Cancer (140-208) Esophagus ( 1 50) Stomach ( I 5 1) Liver (1 55) Lung (1 62) Tuberculosis (010-0 18) Accidcnts (800-949) Motor Vehicle (8 10-929) Non-Motor Vehicle Suicide (950-959)
*P < 0.05 222
1981-1 983 Obscrvcd deaths
1984-1986 PMR
Soldicrs 2450 1.oo 365 I .02 12 1.02 46 I .26 105 1.oo 58 1.21 17 0.40* I006 0.94 438 0.72* 568 I .23* 223 1.41* Students 4000 I .oo 418 1.08 0 0.00 7 1.99 81 1.18 3 0.7 1 12 0.71 249 1 I .04 975 0.94 1516 1.12* 94 0.72* Apprentices 4490 1.oo 501 0.64* 24 0.87 52 0.63* 161 0.65* 71 0.63* 72 0.70* 2127 1.48* 1293 1.60* 834 1.33* 275 1.27* Construction Workers 1560 1.oo 348 1.09 25 1.94* 40 I .07 111 1.12 53 1.04 43 0.95 375 1.07 209 1.09 166 1.05 42 0.71*
198 1-1986
Observed deaths
PMR
Observed deaths
PMR
2095 287 8 30 75 38
I .oo 1.13 1.01 1.18 1.10
4635 652 20 76 180 96 32 1949 83 1 1109 423
I .oo 1.06 1.02 1.23 1.04 1.18 0.44* 0.95 0.71* 1.27* 1.41*
7664 823 0 I1 152 6 24 4720 1877 2843 210
1.oo 1.1 1
0.83*
12520 1729 79 208 498 286 255 4827 2884 1943 626
0.75* 0.87 0.78* 0.71* 0.80* 0.77* 1.43* 1.54* 1.30* 1.19*
1.15
934 393 54 1 200
0.50* 0.96 0.70* 1.31* 1.40*
3664 405 0 4 71 3 12 2229 902 1327 116
1.14 0.00 I .20 1.13 0.77 0.78 1.02 0.95 1.09* 0.95
8030 1228 55 156 337 215 183 2700 1591 1109 35 1
0.81* 0.87 0.84* 0.75* 0.87* 0.8 I * I .40* I .49* 1.29* I.I4*
15
1560 342 14 39 117 59 44 362 207 155 59
1
.oo
1.oo
1
.oo
1.07 1.06 1.01 1.18 1.14 0.94 1.13* 1.19* 1.06 1.05
3120 690 39 79 228 112 87 737 416 32 1 101
0.00 1.61 1.16 0.74 0.74 1.03
0.94 1.12*
1 .oo
1
.oo
1.08 I .49* I .04 1.15
1.09 0.94 1.10* 1.14* 1.05 0.87
Asia-Pacific Journal of Public Health 1992/1993 Vol. 6 No. 4 that should be noted is that not all death certificates had occupational information. However, there was little reason todoubt the representativeness of these deaths within the occupational population from which they were drawn, given the large samples of selected occupations for this study. The occupational analysis was not conducted for females because the numbers in these occupations were not adequate to draw meaningful conclusions.
Fishermen (Total number of deaths = 5,967) Based on the PMR analysis, there was a statistically increased overall cancer mortality(PMR = 1.2 1)for fishermen in Taiwan, and the trend was increasing. Several majorcancer sites showed statistically increased PMRs, including stomach ( P M R = 1.37), esophagus (PMR = 1.58), and liver (PMR = 1.35). Accidental deaths were also increased (PMR = 1.12) due mainly to non-motor vehicle accidents such as drowning. Deaths from motor vehicle accidents (PMR = 0.70) were significantly below the national average. Peasants (Total number of deaths = 68,059) The peasants, the largest of the occupational groups analyzed, had significantly increased mortality for motor vehicle accidents (PMR = 1.18) and suicide (PMR = 1.27). The proportion of death from all accidents increased during the period. Tuberculosis had a slight increase (PMR = 1.07) compared with the total Taiwan population although it had been declining. Cancersofthelung(PMR = 0.88) and esophagus (PMK = 0.89) were statistically lower. Soldiers (Total number of deaths = 4,635) The slight elevation of overall cancer mortality (PMR = 1.06) among soldiers was primarily attributed to the increase in stomach (PMK = 1.23) and lung (PMR = 1.18) cancers. A significant increase was seen in suicide (PMR = 1.41) throughout the two time periods. Deaths from motor ve-
hicleaccidentswerein deficit but nonmotor vehicle accidental deaths (PMR = 1.32) were in excess. Tuberculosis among soldiers was significantly lower than the general population (PMR = 0.44), i.e. less than onehalfofthe expected.
Students (Total number of deaths = 7,664) Because oftheir young age, the majority of deaths were from accidents, which had aslightly increased mortality (PMR = 1.03). The PMR for nonmotor vehicle accidents increased 12% (PMR = 1.12). Suicide was in deficit (PMR = 0.83). The relative number of cancer deaths in students was small but had an 11% increased PMR. It is noteworthy that cancer of the stomach and liver increased as much as 61% and 16% respectively, although their numbers were small.
Apprentices (Total number of deaths = 12,520) Apprentices had significantly increased accidental deaths (PMR = 1.43) f o r both m o t o r vehicle (PMR = 1.54) and non-motor vehicle accidents (PMK = 1.30). Suicide (PMR = 1.19) was also significantly higher than for the general population. As for cancer, apprentices had approximately a 25% deficit across the board.
Construction Workers(Total number of deaths = 3,120) The total number of deaths among construction workers was the smallest among the selected occupational groups. Slightly elevated mortality rates were seen for all cancers (PMR = 1.08), liver cancer (PMR = 1 - 1 3 ,and lung cancer (PMK = 1.09). Cancer of the esophagus was statistically increased (PMR = 1.49) which was primarily due to the 1981-1983 time period. Accidental deathsamong construction workers were significantly higherthan forthegeneral population (PMR = 1.10). Suicide was lower (PMR = 0.87) for the total sixyear study time period, but the PMR increased substantially from 1981-1983 to 1984-1986.
Discussion Infant mortality represents the largest number of deaths in a single age group. This could serve as an index of quality and availability of medical care in the population. The high infant mortality rate on the east coast of Taiwan supported the impression about inadequate medical care among the residents of these areas. This is over and above the lifestyle factors that contributed to much of the increased mortality among adult residents in this region. In general, the infant mortality correlated well with overall mortality for different geographic areas3, suggesting that there are many common risk factors affecting all age groups in the same areas. In otherwords, higher infant mortality was accompanied by higher total mortality and a lower infant mortalitywithlowertotalmortality. However, several notable exceptions were seen. Penghu had a general mortality the same as the average Taiwan mortality, but had an infant mortality 61% higher. Similar patterns were found amongareas where Hakka were the majority of residents. These areas included Taoyuan, Hsinchu county, and Miaoli. The SMRs for total mortality were less than the Taiwan average, 0.93, 0.98, and 0.99, respectively. However, the corresponding IMRs were above the average, 1.15,1.33,and 1.25,respectively. Such a divergence might suggest an inadequacyof preventive and critical care for infants as compared to care for adults and the elderly. Special efforts to improve the prenatal and postnatal care in these geographic areas are needed. Under-reporting of infant mortality in Taiwan has been noted to be as high as 46-96%”. The true infant mortality in Taiwan was estimated to be 11-14 per 1,000‘6, such underreporting must have occurred across all cities and counties so that it should not substantially affect the ranking order presented. I t is likely, however, that the higher the infant mortality, the greater the under-reporting, particularly in the case of the aborigines and rural counties. Thus it cannot be overemphasized that, for improving infant mortality statistics, a two-
223
pronged approach is necessary, i.e. improve infant survival by providing betterhealth carewhileimprovingthe completeness of birth registration regardless ofthe vital status. The reason for the universally observed high male sex mortality ratio remains a mystery and presents a challenge. It is alarming to note that the largest male/female mortality differential in Taiwanwas in the middleage group (ages 15-64 years) with the SMR of 1.8 1 where for every five female deaths there were nine males deaths. This is most disturbing because this age group represents the most productive years in a person’s lifetime. Those years were disproportionately lost by males. Many of the gender gaps observed for different causes could be partially explained by lifestyle risk factors which were more prevalent among males. Similarly, occupational hazards were also more associated witha male-dominated work environment. For example, the twofold increase of lung cancer among males wasprobablyrelated to their 15 times greater cigarette smoking rateI7, and could also be related to their occupational exposures or a combination of b ~ t h ’ ~ .It’ ~can . be hypothesized that the larger the gender gap the greater the chance of an environmental etiology. In this regard, the size of the gendergap could be ranked as follows: cancer of the larynx (SMR = 5.54), pneumoconiosis (SMR = 5.41), cancer of the esophagus (SMR = 5.26), homicide (SMR = 3.62), motor vehicle accidents (SMR = 3. I l), all liver diseases (SMR = 3.04), tuberculosis (SMK = 2.98), cancer of the oral cavity (SMR = 2.97), and emphysema (SMR = 2.77). All of these have been shown to be associated with known environmental The presence ofthe largegender gap made the suspected environmental cause more plausible. Of all the cancers, the largest differentials in sex mortality ratio were cancers of the larynx and esophagus, both with more than fivefold increase in males. These two cancer site have been postulated as being associated with alcohol drinking in addition to cigarette smoking21*22.Men smoked
224
and drank more than women in terms of frequency, concentration of alcohol consumed, and v o l ~ m e ’ Judg~. ing from the size of the gender gap, these two cancers in men have reached an epidemic proportion in Taiwan. The etiological factors for these two cancers were not well studied inTaiwanand wereelusiveat best, other than the established association with cigarette smoking (two to six times higher risk for smokers than non-smokers). The alcohol exerted an independent risk in addition to a synergistic effect with smokingwhich has been reported22. The much-increased mortality ratio for these two cancers sitewhen compared with that for lung cancer which was primarily related to smokingattested to the suggested role of alcohol consumption in their etiology in men. The next two increased sex mortality ratios with largest male excesses were homicide(SMR = 3.62)and motor vehicle accidents (SMR = 3.1 l), both of which were related to increased lifestyle risks in men. Clearly, these two causes of death were exclusively environmental in etiology. Tuberculosis (SMR = 2.98) and emphysema (SMR = 1.7 1) were also increased in males, reinforcing the hazards of certain lifestyles and personal exposure in a crowded environment. Smoking and air pollution aggravated the disparity between the sexes while the role of biological differences was generally not yet recognized as important. Another large differential was seen in cancer of the oral cavity (SMR = 2.87), includingcancerofthe nasopharynx (SMR = 2.47). In view of the oral cavity’s anatomical proximity to the larynx and esophagus, smoking and alcohol could have played an important role in their etiology23.Apparently, such a hypothesis is provocative because these two factors alone are far from adequate in explaining the extraordinary rates of these cancers in the Chinese population. Other etiological agents such as diet may play a role. It has been widely recognized that, with rapid industrialization, occupational hazards would play an increasingrole in developingcancerand
otherconditions. A number ofstudies had reported adverse health effects based on proportionate mortality analyses suggesting possible occupational risks and exposure^^^-^^. Since these PMR analyses were for screening and were preliminary in nature, the findings should be viewed as hypothesis generating. The limitations of PMR statistics should be fully recognized when collection of death certificates is incomplete. When the underlyingoverall mortalityislowforan occupational group, the values of PMR could be Furthermore, the completeness and accuracy of the occupational entries on death certificates in Taiwan are far from desirable. The inherent weaknesses of a death certificate study need to be further evaluated by other niethodsof research. Of the occupations analyzed, the increased risk in overall cancer for fishermen, especially in the case of gastrointestinal cancer, was most noteworthy. Such findings among Chinese fishermen in Hong Kongand Singapore had been repeatedly r e p o r t ~ d ~ ’ Further * ~ ~ . studies regarding their diet, lifestyle, and other risk factors may be worthwhile. It is not surprising to note that death for fishermen from drowning was increased while death from motor vehicle accidents were decreased when compared to the general population. High motor vehicle accidents and suicide mortality amongpeasants implied that they were no longer immune to the side effectsofmechanization or work-related stress even in the rural areas of Taiwan. Relatively cleaner air might have contributed to their low lung cancer mortality. Smoking is highly prevalent among men in Taiwan, but more so among soldiers. There was a long-held tradition in the military services of supplying free cigarettes to soldiers as a fringe benefit. The effect ofthis practice has started to surface with the resulting increase in lung cancer mortality. Soldiers also had a high suicide rate, a not unexpected finding to account for their depressed feelings from limitedcareeropportunitiesand restricted individual freedom. However, the good discipline and the
Asia-Pacific Journal of Public Health 1992/1993 Vol. 6 No. 4 bet ter-t han-average preventive health services among soldiers h a d m a d e motor vehicle accidents a n d tuberculosis m u c h less likely. At present, it is unclear why stomach cancer was high among students. It is important to note that t h e suicide r a t e was not increased despite high pressure to advance to a higher level of education. T h a t apprentices h a d high m o t o r vehicle accidents was understandable since they were often requested t o go on t h e road for errands. T h r e c distinctly different types of statistics were used based on the existing mortality data to assess the role o f e n v i r o n m e n t a l factors in causing mortality variations in Taiwan. Each set of analysis yielded insightful results of unique epidemiological significance that h a d n o t previouslybeen reported. This paper illustrated the usefulness of systematic analyses of routinely collected data. F i n d i n g s from this s t u d y are useful in setting priorities for health a n d safety problems and directing efforts s u c h as health education programs a n d other disease prevention strategies.
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