J Chron Dis 1975, Vol. 28,

pp. 305-310. Pergamon Press. Printed in Great Britain

AMYOTROPHlC

LATERAL SCLEROSIS IN IOWA GURUNANJAPPA S. BALE*

Statistical Bureau, Metropolitan Life Insurance Company, One Madison Avenue, New York, N.Y. 10010 (Received in revised form 1 October 1974) INTRODUCTION

lateral sclerosis (A.L.S.) is a chronic, progressive and degenerative disease. It has been known to the medical profession for over 100 yr and was originahy described by Charcot in 1868. The clinical aspects of the disease have been described elsewhere [l-3]. The characteristics of A.L.S. are particularly interesting. The disease is known to occur more often among males, farmers and heavy laborers [4], with life expectancy about 2-4 yr from the time of onset. Occasionally, some patients have survived for a longer duration, some for as much as 10-20 yr, without complications. The disease’s degenerative process usually begins between the ages of 40 and 70 yr [5]. It has not been established that the disease is hereditary, but the available information indicates that one form may be due to dominant hereditary transmission [1,6]. There is no evidence that the disease has occurred in clusters except among the people of the Mariana Islands in the Pacific and the Kii Peninsula of Japan. And recently, a cluster of three cases was reported in Burlington, North Carolina [7]. Yase [8] found increased deposits of calcium in the central nervous system of A.L.S. patients, and suggested this might be a necessary condition for the development of the disease. Currier and Haerer [4] found no correlation between the amount of lead and mercury in the patients tissue and their A.L.S. in spite of patients’ exposure to these metals in their occupation. Kurland, et al. [9] reported that the average annual ageadjusted death rates for A.L.S., in 1959-1961 among the 50 states, ranged from 0.3 to 1.Oper 100,000 population. Because the rates for most states were between 0.4 and 0.7, they concluded the A.L.S. rates must be considered homogeneous. The recent discovery that the neurological disease kuru, found among the natives of New Guinea who practiced cannibalism, and Creutzfeldt-Jacob in man are due to ‘slow viruses’-viruses with long incubation periods-has shed new light on A.L.S., which is now thought possibly to be due to a slow virus [lo]. Today, the cause of A.L.S. is still unknown and it remains a mystery. In 1972, to identify possible outbreaks of the disease in clusters, the National Disease Center in Atlanta, Georgia, sought information on persons who died of A.L.S. during AMYOTROPHIC

*Formerly Director, Records and Statistics Division, Iowa State Department Iowa. 305

of Health, Des Moines,

306

GURUNANJAPPA S. BALE

1968-1971. This paper presents the results of an expanded study based on that inquiry. The main objective was to study the distribution of the disease in Iowa through mortality records. METHOD

OF DATA

COLLECTION

The Iowa State Department of Health routinely codes information, for statistical purposes, on all death certificates registered with the state. This coded information is stored on computer tapes for the years 1958-1971. Using this tape, information on persons who died of Motor Neuron Disease and Muscular Atrophy (M.N.D.M.A.) was selected for analysis. M.N.D.M.A. deaths were then classified as Amyotrophic Lateral Sclerosis (ICD 356.1 for 1954-1967, ICDA 348.0 for 1968-1971) and Progressive Muscular Atrophy (P.M.A.) (ICD 356.0 for 1965-1967, ICDA 348.1 and 348.2 for 1968-1971). In addition, death certificates of persons who died of M.N.D.M.A. during 1968-1971 were selected to identify occupation of the deceased, which was not available on the computer tapes. During the 14-yr study period, there were 414 M.N.D.M.A. deaths in Iowa. Of these, 19 deaths were for out of state residents and hence were excluded from the analysis. Of the remaining 395 resident deaths, 84.8 per cent (335) died of A.L.S. and 10.4 per cent (41) died of Progressive Muscular Atrophy.

RESULTS

In the United States, M.N.D.M.A. deaths during 1950-1968 show an increasing trend. In spite of a decline in deaths due to Progressive Muscular Atrophy by 74.1 per cent (See Table l), M.N.D.M.A. deaths increased from 1006 in 1950 to a high of 1596 in 1968-an increase of 58.6 per cent in 19 yr. This increase is due to the fact that A.L.S. deaths rose by 114 per cent-from 667 deaths in 1950 to a high of 1410 in 1968. This is probably due to a change in diagnostic custom [9]. The A.L.S. mortality rates during 1950-1968 increased by 1 death per million population every 7-8 yr. The rate increased from 4 per million in 1950, to 5 in 1951, to 6 in 1959 and to 7 in 1966. It is expected that the rate in 1973 will be about 8 per million population if the present trend prevails. During 1958-1971, Iowa registered 335 A.L.S. deaths among its residents. In 1961, there were 40 deaths, a rate of 14.4 per million population (a record high number of A.L.S. deaths); a low of 16 deaths was reached in 1963, a rate of 5.8. The A.L.S. deaths and rates show a cyclic pattern, reaching a maximum every 4th year; the succeeding peak is always lower than the previous high. Mortality data for Iowa show neither an increase in the incidence of A.L.S. nor a shift in the diagnostic custom. The latter is probably due to the availability of good neurologic diagnostic facilities in Iowa and those in the neighboring states of Minnesota, Wisconsin, Illinois, Missouri, and Nebraska, which are easily accessible from any part of Iowa. Further, according to a recent survey of physicians in Iowa Ill], 40 neurologists (including child neurologists) practice in Iowa, 23 of them in privately. Hence, it is possible that more correct diagnoses of A.L.S. would have been made in Iowa than in some other regions in the United States.

1225

1147

1589

1589

1438

1966

1965

1066

1011

937

1277

1273

1230

1174

1089

1962

1961

l%O

1959

1958

1957

734

728

770

667

1001

1062

1103

1006

1953

1952

1951

1950

317

296

304

246

260

*Source: Vital Statistics of the United States. DHEW.

738

1032

1954

211

748

988

203

197

195

169

158

154

153

142

0.5 0.5

0.7 0.7 0.7 0.6

40 21 21 17 -

-

45 26 18 -

Vol. 1, 1950-1968.

23

0.2 0.5 0.4

0.1 0.7 0.7

0.2

0.2

0.2

0.5

0.6

0.5

0.2

0.5 0.6

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.5

0.6

0.6

0.6

0.6

0.1

0.1

0.1

0.1

0.1

0.0

-

0.5

0.6

0.7

0.7

0.8

23

0.6 0.6

28

28

25

0.7

0.6

0.7

0.7

36

104 16

0.1

32

35

115

0.7

0.7

-

22

0.8

30

29

124

0.8 0.8

23 25

25

25

11

23

-

P.M.A.

-

-

0.1 -

0.8

0.9

1.6

1.0

1.0

0.9

1.3

1.3

1.0

0.9

1.0

0.8

0.9

Rate per 100,000 population United States* M.N.D.M.A. M.N.D.M.A. A.L.S. P.M.A.

82

27

22

27

M.N.D.M.A.

Iowa A.L.S.

109

-

P.M.A.

Number of deaths

849

854

1164

1955

1956

1068

1427

1963

1191

1370

1409

1964

1349

1355

1410

1596

1968

1967

1969

-

-

United States* M.N.D.M.A. A.L.S.

0.1 0.1

0.8

-

0.6 -

-

-

-

-

-

-

-

0.0

k? b 0” 2, _. 1 0” 9

0.1 1.4 0.8

z 5

5

% Y 2 a t;

0.8

0.0

0.1

0.1

0.0 0.1

0.3 0.1

0.6

0.8

1.1

1.1

0.9

0.8

0.2 0.0 0.9

0.1

P.M.A.

0.6

0.8

Iowa A.L.S.

NU~~BER OF DEATHSAND RATESDL’ETO MOTORNEURONDISEASE AND MUSCULAR ATROPHY,AMYOTROPFIIC LATERALSCLEROSIS, AND PROGRESSIVE MUSCULAR ATROPHY,UNITED STATES1950-1968, IOWA 1958-1971

1970

1971

Year

TABLE 1.

308

GURUNANJAPPAS. BALE

Sex Previous studies report that A.L.S. occurs among males more often than among females, with a ratio of anywhere from 2 to 4 in favor of males [3]. However, Mackay [5] reports a ratio of 2.5 : 1 in favor of males, based on 70 cases. The U.S. mortality data indicate a smaller ratio than that reported by several authors. The ratio is smaller than 2, and in recent years it appears to be closer to 1.5 : 1 in favor of males. In Iowa, there are more A.L.S. deaths among males than among females (62 per cent (208) among males and 38 per cent (127) among females), giving a sex ratio of 1.6 in favor of males. In 1967, there were more deaths among females and in 1966, the number of deaths was the same among both sexes. The sex ratio during the 14-yr study period ranged from a high of 4.3 in favor of males in 1963 to a low of 0.9 in 1967.

During the study period 1958-1971, 87.7 per cent of the deaths occurred among persons between 40-70 yr of age. Except for one 18-yr-old female, all A.L.S. death victims were persons 30 yr or older. Almost 60 per cent of the deaths occurred among persons 60 and above, about 98 per cent of the deaths occurred among persons 40 and above. The average age at death for males was 62.2 yr and it was slightly higher than that for females (61.1 yr). Since 98 per cent of the deaths occurred among persons over 40 yr of age, the results of this study confirm the previously reported findings that the disease occurs predominantly among persons 40 and older.

FIO. 1.

Average annual age-specific death rates for amyotrophic lateral sclerosis by sex, Iowa 1958-1971.

The figure shows average annual mortality rates by sex and age group for the years 1958-1971 combined. The rates for both men and women peak at ages 65-69, but for males there are secondary peaks at ages 55-59 and W-84. The reasons for these secondary peaks are unknown.

Amyotrophic

Lateral Sclerosis in Iowa

Occupation

According to the 1970 Census, Iowa has about l,lOO,OOOpersons 16 yr of age and older in the labor force, about 12.5 per cent of whom are engaged in farm and farmrelated work. A.L.S. deaths among farmers during the study period accounted for 21.8 per cent (73). An additional 29.2 per cent (98) A.L.S. deaths occurred among housewives. The working class-which includes laborers, craftsmen, foremen, and service workers-account for 19.7 per cent (66) of the total A.L.S. deaths. The remaining 98 A.L.S. deaths occurred among other occupations-professionals, clerical and the like.

Familial distribution

At least two A.L.S. deaths were identified in one family. The information on the death certificate shows that ‘AT’, a farmer (married), died at the age of 65. He lived about 3 yr from the date of onset of the disease. Two years later his brother ‘HT’, a meat cutter (married), died at the age of 60 from A.L.S. He survived about 2 yr from the date of onset of disease. No other information is available.

Geographic distribution

During the 14-yr period 1958-1971 there were no A.L.S. deaths in 18 counties, l-4 A.L.S. deaths in each of 60 counties, and 5-8 A.L.S. deaths in each of 14 counties. The remaining 7 counties each had 10 or more deaths (107 deaths in all, or 32 per cent of the A.L.S. deaths). Dubuque County had 5 deaths in 1967, the highest number of A.L.S. deaths registered by a county in a single year. In 1971, Poweshiek had 3 A.L.S. deaths. In other counties, the number of A.L.S. deaths ranged from zero to two. The average annual mortality rate by county per 100,000 population, which ranged from 0.3 to 3.0 for counties reporting one or more deaths during the study period, does not indicate a geographic pattern in A.L.S. mortality, confirming the findings by Kurland et al. [9].

SUMMARY

This study was based on information derived from deaths registered in Iowa during the years 1958-1971. The results of this study confirm the previously reported findings regarding A.L.S. The disease is found predominantly among persons 40 yr of age and above; there are more deaths among males; a sex ratio of 1.6 : 1 in favor of males, and more deaths among farmers. The life expectancy from the date of onset is about 2-4 yr. There is no geographic pattern in A.L.S. death rates. Further, the mortality data for Iowa show neither an increase in the incidence of A.L.S. nor a shift in the diagnostic custom.

Ackrrowledgements-The the manuscript.

author is grateful to the referees for their helpful suggestions on improving

310

GURUNANJAPPAS. BALE REFERENCES

1. 2.

3. 4. 5. 6.

Myrianthopoulos NC, Brown IA: A genetic study of progressive spinal muscular atrophy, Am J Hum Cen 6: 387, 1954 Amyotrophic lateral sclerosis in Alamance County, North Carolina, 1960-1971, Administrative Reoort from Viral Disease Branch. Health Services. Mental Health Administration. CDC Atlanta, 1972 Kurland LT: Descriptive epidemiology of selected neurologic and myopathic disorders with particular reference to a survey in Rochester, Minnesota. J Chron Dis 8: 378, 1958 Currier RD. Haerer AF: Amyotroohic lateral sclerosis and metallic toxins. Arch Envir Hlth _ _ 17: 712, 1968 Mackay RP: Course and prognosis in amyotrophic lateral sclerosis, Arch Neural 8: 117, 1963 Kurland LT, Mulder DW: Epidemiologic investigations of amyotrophic lateral sclerosis: Familial aggregations indicative of dominant inheritance. Neurology (Minneap) 5: 182 and 249, 1955 ____

Hoehberg FH, Bryan II. JA, Whelan, MA: Clustering of amyotrophic lateral sclerosis. Lmcet 1: 34, 1974. 8. Yase Y: The pathogenesis of amyotrophic lateral sclerosis. Lancet 2: 292, 1972 9. Kurland LT, Kurtzke JF, Goldberg ID: Amyotrophic lateral sclerosis and other motor neuron diseases, Chapter 5, Epidemiology of Neurologic and Sense Organ Disorders. Cambridge: Harvard University Press, 1973 10. Holland JJ: Slow, inapparent and recurrent viruses, Scient Am, 230: 33, 1974 11. Reeve AM, Bale GS, Grace MW, Leonard D: Survey of physicians, Iowa 1972, Iowa State Department of Health, Des Moines, Iowa 1973 7.

Amyotrophic lateral sclerosis in Iowa.

J Chron Dis 1975, Vol. 28, pp. 305-310. Pergamon Press. Printed in Great Britain AMYOTROPHlC LATERAL SCLEROSIS IN IOWA GURUNANJAPPA S. BALE* Stati...
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