PREVENTIVE
MEDICINE
4, 258-267
Correlates
of Hypertension
WILLIAM Environmental
(1975)
E. MORTON
Medicine
AND
Among
Young
Men1
JOHN C. KNUDSEN
Division, University of Oregon Medical Portland, Oregon 97201
School,
Among a cohort of 15,887 Oregon young adult males born during 1939-1941 and examined during 1957-1969, 600 (3.8%) were judged to have definite hypertension, 417 (2.6%) had labile or borderline hypertension, 200 (1.3%) were normotensive but had a history of secondary to carprevious blood pressure elevation, and 31 (0.2%) had hypertension diovascular or endocrine disorders. The following medical conditions were noted to increase the risk of definite hypertension prevalence (in order of strength of association): obesity, hearing loss, renal disorders, respiratory allergies, colorblindness, peptic ulcer, and blood or urine sugar disorders. The association with colorblindness was previously unreported. The strong association with hearing loss excluded suppurative middle ear disease and hereditary nephritis but could have been based on nonsuppurative ear disease or noise exposure. Since the registrants’ average age was 21.5 years at examination, the causes of these associations were operative during childhood and adolescence.
For some time it has been evident that hypertension is nonuniformly distributed around the world, within nations, and even within states and cities (9,12,15,16,21,22,25,28,32,39,48,50,52). The extent of geographic variation of morbidity is known for relatively few jurisdictions, and causes are still unclear, although stress, drinking water, and dietary constituents have been the leading suspects (6,15,17,28,33,35,45). Most of our epidemiologic impressions have been derived from mortality rates which have fallen dramatically over the past 25 years. However, mortality data can be suspected of reflecting different outcomes of treatment as much as different risks of disease incidence, and few investigators are satisfied with this source of data. Very few sources of chronic disease morbidity data cover an entire state, so that those sources should be utilized whenever possible. This paper will describe the methods and results of the survey of medical records of Oregon young men who were candidates for entrance into the armed forces during 1957- 1969. METHODS
The study population included all Oregon Selective Service registrants born in the years 1939, 1940, and 1941, the same birth year cohort as had been previously studied in Colorado. In Oregon the record review was conducted at the state headquarters office rather than at each local board office as was done in Colorado (32,33). The record review began in 197 1 and continued for a year as all registration folders were forwarded from the 32 local boards to state headquarters for destruction. Among the 37,101 Oregon registrants for these birth ’ This study was financially supported by the Oregon State University Environmental Health Science Center, the Oregon Heart Association, and the University of Oregon Medical School. 258 Copyright 0 All rights of
1975 by Academic
Press, Inc. reproductionin any form reserved.
CORRELATES
OF HYPERTENSION
259
years were 15,887 (43%) whose files contained medical examination forms and/or medical diagnosis statements, all of which were retained for this study. This meant that the medical records were immediately available to check coding accuracy, which was a distinct advantage over the Colorado study. Although many men had more than one medical examination in their files, descriptive data including body size and blood pressure were coded as of the first examination available. Ages ranged from 17 to 26 years at first examination, with 22 the mode and 21.5 the mean age. Blood pressure measurements had been taken in the sitting position, and the lowest values obtained were recorded and coded. The majority of individuals with elevated blood pressure levels had been retested after varying periods of rest, often after several days or weeks had elapsed. Usually those whose elevated initial blood pressure values had not been rechecked were persons whom the armed forces considered undesirable for other reasons in addition to their blood pressure. An armed forces entrance examination probably constitutes more of a stress situation than the average medical examination, but the blood pressure recording procedure attempts to compensate by use of rest periods, recumbent position, and retesting after the lapse of several weeks or months before a hypertension diagnosis is applied. For individuals aged 35 years or less, the armed forces officially rejected blood pressure levels above 150/90 mm Hg until December 1960 and above 140/90 subsequently. Despite the systolic criterion change, a study by Karpinos has shown that armed forces entrance examiners have generally tended to continue to make hypertension diagnostic decisions based on the 150-mm standard and to markedly underrecord systolic pressure from 142-154 mm Hg since that time (24). Among 529 Oregon registrants with diagnosed hypertension, only 26 (4.9%) had a minimum systolic pressure of 142-150 mm Hg plus a normal diastolic pressure. Included among “definite” hypertensives in this paper were the 529 registrants diagnosed as such plus 71 individuals with minimum blood pressure levels greater than 150/90 who usually had been rejected for other causes. Auditory acuity was usually tested with Rudmose audiometers using frequencies of 500, 1000, 2000, 3000, 4000, and 6000 cycles for each ear, although criteria of acceptibility are based only on frequencies of 500, 1000, 2000, and 4000 Hz. For this study a significant hearing loss was defined as a loss of 50 or more decibels in either ear at any frequency tested, which differs from the armed forces criteria for medical fitness. Color vision was most commonly tested with the American Optical Company pseudoisochromatic plates, but occasionally the Ishihara test was used. RESULTS
Table 1 shows the geographic distribution of the population at risk, the sample examined, and the identified ethnic groups. Although the armed forces recruitment procedure is known to be more successful among lower socioeconomic population groups and, therefore, distinctly biased in that direction (31), the sampling fraction for medical examinations was relatively uniform, ranging from
260
MORTON AND KNUDSEN TABLE
1
OREGON SELECTIVE SERVICE REGISTRANTS BORN IN 1939-1941 AND EXAMINED IN 1957-1%9. ETHNIC DISTRIBUTION BY GEOGRAPHIC REGIONP
Registrants Ethnic status of those coded Coded Geographic region Western coastal Portland Metro. Willamette So. Cascade Eastern Columbia R. Central Over 4000 ft Snake R. Oregon
Listed
Span. Amer.
Other white
Number
%
Black
Oriental
30972 3621 13850 9552 3949
13144 1575 6012 3998 1559
42 43 43 42 39
77 5 49 20 3
12733 1550 5675 3961 1547
191 2
51 1
188 1
44
0
6129 1993 1223 1369 1544
2743 904 511 626 702
45 45 42 46 45
41 10 7 6 18
2567 871 442 594 660
37101
15887
43
118
15300
Amerindian
Other and unknown
3 3
1.5 4 5 5 1
77 13 51 8 5
5 0 0 2 3
14 3 1 2 8
45 13 15 16 1
71 7 46 6 12
1%
65
60
148
a Geographic regions contain the following counties: Coastal: Clatsop, Columbia, Coos, Curry, Lincoln, Tillamook. Portland Metropolitan: Clackamas, Multnomah, Washington. Wihamette Valley: Benton, Lane, Linn, Marion, Polk, Yamhill. Southern Cascade: Douglas, Jackson, Josephine. Columbia River: Gihiam, Hood River, Morrow, Sherman, Umatiha, Wasco. Central: Crook, Deschutes, Grant, Jefferson, Wheeler. Over 4000 ft elevation: Hamey, Klamath, Lake. Snake River: Baker, Malheur, Union, Wallowa.
38% to 46% among the regions listed in Table 1 and from 36% to 52% among individual local boards. The relative ethnic homogeneity of Oregon is attested by the fact that 96.3% of those examined were classified as “other white.” Blacks, the largest minority group, were almost entirely located within Portland, whereas Amerindians were predominantly from eastern Oregon. Ethnic status can be expected to have little influence on hypertension distribution in Oregon. Table 2 shows the age and ethnic distribution of the four diagnostic categories of hypertension. Definite hypertension prevalence increased from age 18 to age 22 at first examination, then fluctuated among subsequently examined registrants. Borderline hypertension showed a complementary tendency to be more common at younger ages and less common at older ages, suggesting that even within this narrow age span, age tends to convert labile to relatively stable hypertension. Older examinees were more apt to have a history of previous blood pressure elevation, while hypertension secondary to cardiovascular or endocrine conditions was more apt to be seen among younger applicants. None of the ethnic differences in definite hypertension are significant, although with larger numbers the Chicano rate elevation might become so.
CORRELATES
OF
TABLE
261
HYPERTENSION
2
PREVALENCE OF HYPERTENSION AUONG OREGON SELECTIVE SERVICE REGISTRANTS CLASSIFIED BY AGE AT TIME OF FIRST EXAMINATION AND BY ETHNIC GROUP. RATES PER 1000 CODED Hypertension
Age (yr)
Total registrants coded
Deli&e
Borderline
No.
Rate
No.
Hx only
Rate
No.
Secondary
Rate
No.
Rate
17 18 19 20 21 22 23 24 25+ Total
498 1,360 878 813 2,376 6,474 1,249 1,004 1,235 15,887
11 9 12 13 96 330 37 45 47 600
22 7 14 16 40 51 30 45 38 38
18 47 28 19 71 166 20 25 23 417
36 35 32 23 30 26 16 25 19 26
0 6 5 1 25 112 11 16 24 200
0 4 6 1 11 17 9 16 19 13
2 4 4 0 7 12 0 1 1 31
4 3 5 0 3 2 0 1 1 2
White Black Chicano Oriental Amer. Indian Other unknown
15,300 1% 118 65 60 148
579 7 7 3 3 1
38 36 59 46 50 7
407 6 3 0 0 1
27 31 25 0 0 7
194 1 1 1 1 2
13 5 8 15 17 14
29 0 2 0 0 0
2 0 17 0 0 0
Table 3 shows the frequency of definite hypertension in the presence or absence of various other medical conditions. Some of these associations were expected, others were not. The renal disorders listed in Table 3 add up to more than 521 because some individuals could be classified into more than one category. Other and unspecified renal disorders included 19 with hydronephrosis or other ureteral disorders and nine with major congenital renal malformation. The frequency of definite hypertension was elevated in any and all renal disease categories in contrast to the majority of registrants with no history of renal disorders. However, the small numbers at risk in most categories limit the significance of these results except for previous glomerulonephritis and the other and unspecified renal disorders which display significant elevations of hypertension prevalence. Individuals with blood or urine sugar disorders were imperfectly divided into diabetic and nondiabetic categories because the criterion for rejection was simply the presence of persistent glycosuria of any cause, and further definition was not required. The majority of those identified as diabetics were so certified by letter from the personal physician who briefly listed the diagnosis and usually a need for insulin and regulated diet but nothing else. Thus, hypertension is underrecorded among identified diabetics in this study. Many of those with otherwise unspecified glycosuria had been labeled as having renal glycosuria, but proof was unavailable more often than not, so that perhaps most of these subjects should
MORTON AND KNUDSEN
262
TABLE 3 PREVALENCE OF DEFINITE HYPERTENSION AMONG OREGON SELECTIVE SERVICE REGISTRANTS WITH VARIOUS OTHER CONDITIONS. RATES PER 1000
Number of registrants
Past or present other conditions Renal disorders
None Any
Glomerulonephritis Pyelonephritis Renal trauma Nephrolithiasis Albuminuria, NOSb Other and unspecified Blood or urine sugar disorders
None Any
Diabetes mellitus Glycosuria, NOS* Hypoglycemia Respiratory allergies
None Any
Asthma Hay fever
Definite hypertension
Significance of difference from nones
No.
Rate
15,366 521
561 39
37 75
0.002
116 141 57 40 168 89
15 9 4 2 11 10
129 64 70 50 65 112
0.003 0.19 0.33 0.70 0.14 0.025
15,626 261
582 18
37 69
0.043
140 112 9
6 10 2
43 89 222
0.73 0.054 0.18
14,288 1,599
516 84
36 53
0.003
721 878
38 46
53 52
0.046 0.024
Color blindness
None Any
15,227 660
561 39
37 59
0.018
Ear disorders
None Any
14,075 1,812
485 115
34 63
O.OOOOO6
1,155 186 459 12
84 7 24 0
73 38 52 0
O.OOOOOl 0.77 0.086 0.019
Hearing loss alone Hear. loss and Mid. ear dis. Middle ear disease alone Congenital malformations Peptic ulcer
None Any
15,241 646
562 38
37 59
Obesity
None Any
15,315 572
375 225
24 393
a According to Z =
x,+n,
Xl@ - a ; x,(B - YJ N N2 b NGS = not otherwise specified.