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Socioeconomic differentials in prognosis following episodes of coronary heart disease
J Chron Dis 1971, Vol. 23, pp. 881-889. Pergamon Press. Printed in Great Britain
SOCIOECONOMIC DIFFERENTIALS IN PROGNOSIS FOLLOWING EPISODES OF CORONARY HEART DISEASE* Z. HRUBEC, Sc.D. Statistician,
Follow-up
Agency,
National Academy of Sciences-National Washington, D.C. 20418, U.S.A.
Research
Council,
Associate Director for Clinical Applications, National Heart and Lung Institute, National of Health, Bethesda, Maryland, U.S.A.
Institutes
and W. J. ZUKEL, M.D.
(Received 10 February 1970; in revised form 10 August 1970)
INTRODUCTION
between socioeconomic characteristics and the risk of developing coronary heart disease is well documented [l--4]. There are also numerous reports on clinical factors such as the severity of the initial attack, fever following the attack, and leucocytosis, which affect the prognosis of coronary heart disease after it develops [S, 61. However, very little has been reported on the relationship of socioeconomic characteristics to prognosis in this group of diseases. The purposes of this report are to present data on prognosis for men with various social and economic traits and to discuss the possible significance of the differences in prognosis for the management of the cardiac patient. THE ASSOCIATION
MATERIALS
AND
METHODS
A detailed description of the materials and methods of the study has been reported [7]. Information on survival and mortality was obtained from the files of the Veterans Administration for 2234 Army veterans who were admitted to service hospitals with first attacks of coronary heart disease between June 1943 and December 1944. *This work was carried out by the Follow-up Agency, National Academy of Science-National Research Council, 2101 Constitution Avenue, Washington, D.C. 20418, under contract number PH43-63-1139 with the National Heart Institute, National Institutes of Health, Bethesda Maryland. The investigation is part of a program of studies of the Follow-up Agency, developed by the Committee on Veterans Medical Problems and carried out in co-operation with the Veterans Administration, the Army, the Navy, and the National Institutes of Health. The conduct of this study depended on medical and other records of the Department of Defense, the Veterans Administration, and the National Archives and Records Service, GSA. We are indebted to these agencies, particularly to their records management personnel, for the ready access that they generously provided to the required material. We gratefully acknowledge the work of Bernard M. Cohen, Ph.D. (deceased 22 October 1962), in definition of the sample and preparation of the study materials, and the assistance of other staff of the Follow-up Agency: Mr. A. Hiram Simon, Chief of operations; Miss Vivian A. Heidenblut, the supervisor directly responsible for records abstracting and coding; and Mrs. Lucille P. Pogue for computational and analytic work. 881
Z. HRUBEC and W. J. ZUKEL
882
Various items of social, demographic, and economic information were obtained from the records of induction or enlistment into military service, and medical information was abstracted from the Army hospital records. Survival through 31 December 1962 was determined using the records of the Veterans Administration. A recent methodologic exploration indicated that the VA Master Index records the fact of death for 98 per cent of deceased white World War II veterans, regardless of prior medical history. To ensure the application of uniform diagnostic criteria two reviewers independently examined the medical information in the service records. There was some disagreement between them on the type of coronary heart disease but they both classified 68.4 per cent of the 2234 cases as belonging to this class of disorders [7]. The present work is based on the diagnoses of coronary heart disease made by only the first reviewer (W.J.Z.). Included here are 301 patients on whom there was disagreement about the presence of coronary heart disease. Of these latter patients 229 are considered in the present work as angina pectoris or coronary insufficiency and the remaining 72 are scattered in various diagnostic groups. The difference between the reviewers could have resulted from variation in the severity of signs or symptoms used for classification. In the work described here we thought it important to include the milder cases in order to maintain meaningful variability in prognosis. While the data presented reflect only one reviewer’s diagnoses we do evaluate relationships within groups of varying diagnostic certainty including ones based on objective electrocardiographic findings. We also analysed but do not present data on the group diagnosed as coronary heart disease by both reviewers since the results of that work are essentially redundant. Among the 1829 cases identified as coronary heart disease on the first review there TABLE 1. MEDIAN AGE AT ADMISSION AND NUMBEROF PATIENTSIN GROUPS BASEDON DIAGNOSIS,EDUCATION,AND OCCUPATION. WHITE MALESALIVE 6 months AFTERFIRSTADMISSION Median age at admission
No. with known age
Diagnosis :* MI, CO, CT AP, CI Other diagnosis
40.7 40.8
572 850 72
Education : Completed college Did not complete college
42.4 39.3
455 1039
41.7
248
43.1 38.2 48.9 38.9
230 769 164 83
40.3
1494t
Physicians and surgeons Other professional, technical. and kindred Not professional In service before 1941 Other Total *See text for explanation of abbreviations. tAge at admission was not known for one patient.
39.7
Socioeconomic
Differentials in Prognosis following Episodes of Coronary Heart Disease
883
were 105 nonwhite and 1724 white patients. The number of nonwhite patients is small and they have not been included in this analysis. In evaluating the significance of socioeconomic variables in prognosis it is useful to distinguish between the period of acute attack (lasting hours or days), the period of hospital convalescence (lasting weeks or months), and the period following discharge from the hospital. In the acute illness prognosis is related primarily to the clinical aspects of the disease. Since our present interest is primarily in long-term prognosis, most of the analyses have been based on the 1495 white Army veterans with a review diagnosis of coronary heart disease still alive 6 months after admission to the hospital. The median age of men with various characteristics is given in Table 1. The oldest patient was age 70, and 87 per cent of the men were less than 50 yr old at the time of the first admission. Therefore, most subjects were probably concerned with occupational adjustments to their disease. The median ages vary somewhat with occupation and education. Men completing college, physicians, and men in other professional, technical, and kindred occupations were older than the total group. Men in military service before 1941 were professional soldiers and were appreciably older. No meaningful differences in age were found between the three diagnostic groups of myocardial infarction, coronary occlusion, and coronary thrombosis (MI, CO, CT); angina pectoris and coronary insufficiency (AP, CI); and the other coronary diagnoses. Because of the age differences between various groups, age-adjusted percentages have generally been used in the analysis and their statistical significance was evaluated using tests described in reference 8. Unless specified otherwise, the age adjustment was direct and the weights used were derived from the age distribution of the total group of 1495 cases. RESULTS
Survival of men in different occupational groups is shown without age adjustment in Table 2. Occupations reported at entry into service are classified according to the 1950 census code of occupations [9]. The group of physicians and surgeons appears TABLET. PERCENTSURVIVING~~ yr AFTERADMISSION BYOCCUPATIONGROUP. WHITE MALES ALIVE 6 months AFTER ADMISSION WITH ANY DIAGNOSED CORONARY HEART DISEASE
Occupation group
Per cent
Total No.
Physicians and surgeons Other professional, technical, and kindred Managers and farmers Clerical and sales Operatives, craftsmen, foremen Personal service workers Laborers Stated, not classifiable In service before 1941 Students and unknown
71.9
249
48.3 44.4 48.5 54.3 41.8 58.1 54.7 34.8 50.0*
230 223 134 302 67 43 75 164 8
Total
51.7
1495
*Indicates that percentage is based on denominator
of 20 or less.
884
Z. HRUBEC and W. J. ZUKEL
to have a lower mortality than any other occupational grouping. The prognosis of men in service before 1941 seems less favorable, 34.8 per cent of them survived 18 yr. These men are appreciably older than men in other occupations. Their survival is comparable to that of the oldest age groups, but because of their extreme age distribution, adequate age adjustment is not possible. In the other groups, age adjustment of the per cent surviving 18 yr yields 71.6 per cent for physicians and surgeons, 50.3 per cent for other professional, technical, and kindred occupations, and 46.7 for all other occupations combined except men in service before 1941. TABLE 3.
AGE-ADJUSTEDPER
CENT*
SURVMNO BY years AFTER ADMISSION, OCCUPATION,AND p ADMISSION WITH ANY DIAQNOSED CORONARY HEART
EDUCATION. WI-IRE MALESALM? 6 months
DISEASE
Yr after admission Occupation
group
Physicians, surgeons Any except physicians, and surgeons Other professional, technical, and kindred Other professional, technical, and kindred Not professional, classifiable Not professional, classitiable All other Total
Highest educational level
No. alive at 6 months
5
10
15
18
Beyond college
94.4
86.7
75.2
71.9
249
Beyond college
89.9
74.9
59.9
54.8
87
College grad. only
91.5
75.8
63.4
58.1
62
< College grad.
86.3
69.2
57.4
49.6
88
College grad.
85.5
59.3
44.0
38.7
37
< College grad. AnY -
86.3 80.1 86.8
70.2 62.4 71.9
55.4 50.2 58.4
47.4 43.8 51.6
704 268 1495
*Adjusted to the age distribution
of the total group.
Table 3 presents age-adjusted survival by years after admission, educational level, and occupation. The usefulness of the U.S. Census classification in the scaling of occupations has been questioned [lo]. Admittedly the group designated as professional, technical, and kindred is very broad. To achieve greater specificity in the subsequent analysis and terminology, we have used the following socioeconomic groupings : (4 Physicians, including surgeons, not in service before 1941. (b) Other professional, including the 87 men with graduate education and the 62 in professional, technical and kindred occupations who completed college, not in service before 1941. (4 Non-professional, including those not in professional, technical and kindred occupations with less than graduate education and all those not completing college, not in service before 1941. (4 All not classified above. In the other professional group, those with graduate education were not differentiated by occupation. A detailed review of the individual codes indicated that only 19 of these patients were not coded as having a professional, technical or kindred occupation. Several of the latter involved questionable coding decisions such as inclusion of a ‘painter’ among craftsmen rather than artists. The better survival of physicians
Socioeconomic
Differentials
in Prognosis following Episodes of Coronary Heart Disease
885
over the other groups is again apparent in Table 3. The other professional group had a somewhat better prognosis than the non-professional (p < 0.05). The differences in survival among the various groups in Table 3 appear to be similar at different points throughout the 18-yr period. TABLE 4. AGE-ADJUSTED PER CENT SURVMNG SOCIOECONOMIC GROUP AND DIAGNOSIS. WHITE AFTER ADMISSION
18 yr AFTER ADMISSION BY MALES ALIVE AT 6 months
Diagnosis* MI, CO, CT
% Socioeconomic grouping*
AP, CI
%
surviving 18yr
Total No.
surviving 18yr
Total No.
Physician, surgeon Other professional Not professional, classified Other
50.6 50.2 32.7 35.2
45 56 325 146
77.4 62.3 55.7 53.9
200 84 313 194
Total
36.6
572
61.3
851
*See text for definition of groups.
Of the 1495 patients, there were 572 with the review diagnosis of MI, CO, CT and 851 with the review diagnosis of AP, CI. In Table 4 are presented adjusted 18-yr survival percentages by diagnosis and socioeconomic grouping. In the diagnostic group of AP, CI there was a considerable difference between the physicians and the other professional group (p < 0.05). In the diagnostic group of MI, CO, CT the difference was primarily between the physicians and other professionals compared to the non-professional group (p < 0.01). For both diagnostic groupings combined the other professionals had a better prognosis than the non-professionals (p < 0.05). The age-adjusted per cent surviving 18 yr was higher among Jewish patients (62.7 per cent) than among patients of other religious afhliation (50 .O per cent, p < 0.01). However, a fairly strong association exists among education, occupation, and religious affiliation. When crude survival percentages were compared separately for physicians and men in non-professional occupations without a college degree, Jewish patients again had a better prognosis in both groups (p c 0.05). Age adjustment of percentages within occupation groups was difficult because the data were considerably fragmented. To the extent that age adjustment was feasible within occupation groups, it seemed to reduce the apparent favorable prognosis of Jewish patients somewhat, and the differences could not be distinguished clearly from sampling fluctuations (~“0.10). Table 5 shows survival by marital status at entry into service and years after admission. Married men had favorable prognosis compared to single men (p < 0.05) or those who were divorced, separated, or widowed (p < 0.01) when an age-adjusted comparison was made. A similar relationship was seen within each of the two diagnostic groups.
HRUBECand W.
J. ZUKEL
TABLET. AGE-ADJUSTED PERCENTSURMVINGBYYEARSAFTERADMISSIONAND MARITALSTATUSATENTRYINTOSERVICE. WHITEMALESALI~E 6months ADMISSION
WITH
ANY
DIAGNOSED
CORONARY
HEART
Yr after admission
Married Single Divorced, separated Unknown
ARER
DISEASE
5
10
15
18
No. alive at 6 months
89.4 86.0
75.3 69.7
62.9 55.7
55.0 49.3
758 459
77.4 90.9
61.5 84.7
45.6 77.8
40.8 70.3
230 48
DISCUSSION
The appearance of differences in the survival of various socioeconomic groups following the diagnosis of coronary heart disease raises questions about the mechanisms which produced these findings. Do different disease processes go on in the various groups, is the disease detected at different stages, or are there differences in the medical regimens and stresses in the follow-up period? To what extent is the experience of this somewhat unusual sample of patients more generally applicable? The patients studied by us do not include the oldest ages which represent the bulk of many hospital series. Only survivors of the initial hospitalization have been included. The men have been screened through the military induction examination which eliminated those with obvious cardiovascular and other significant pathology. We are dealing with first episodes of the disease found in a setting in which the threshold of detection is low. The latter is reflected partly by the high proportion of cases diagnosed as angina pectoris or coronary insufficiency (56.9 per cent). In a comparably selected group of survivors of an initial episode of myocardial infarction uncomplicated by other cardiovascular or metabolic diseases and with a median age of 35 yr, Gertler et al, using life-table methods, estimated that 44.5 per cent of the patients were surviving 18 yr after diagnosis [ll]. Among our patients, the percentage surviving 18 yr with the review diagnosis of MI, CO, CT (adjusted to the age distribution of Gertler’s group) is 43.2 per cent. No reports on the survival of comparably selected groups of angina pectoris cases are known to us, but it seems reasonable that their experience should be better than that of the MI, CO, CT group. After age-adjusting to the ages of Gertler’s series, the 18-yr survival of our AP, CI patients is 68.4 per cent, considerably higher than the percentage for the MI, CO, CT group. Differences in the manifestation of coronary disease in the various socioeconomic groups could well result in differences in survival. According to evaluation of acute prognosis by others [2, 6, 12, 131 the determining factors are the nature of the acute attack and related clinical variables. Within diagnostic groups we found no appreciable association between mortality in the first 6 months and socioeconomic factors, but there were considerable differences between the various socioeconomic groups in the proportion of patients diagnosed as MI, CO, CT. Among physicians, 18.1 per cent were in that diagnostic group; among the other professional occupations, 37.6 per cent; and among men in non-professional occupations, 43.7 per cent.
Socioeconomic
Differentials
in Prognosis following Episodes of Coronary Heart Disease
887
Similarly, among Jewish patients 25.3 per cent were diagnosed with the more severe forms of coronary disease, while for the other religions, 39.7 per cent were so diagnosed. The differences with marital status are less remarkable, 36.4, 40.7, and 43.5 per cent, respectively, among married, single, and separated men. It therefore appears that the differentials in prognosis identified in our study are partly due to differences in the severity or manifestation of the disease at admission. The variation in the proportion of the MI, CO, CT diagnoses in various socioeconomic groups and the low mortality among the AP, CI case raise the possibility of different degrees of severity with socioeconomic traits or possibly differential admixture of patients free of coronary disease in the AP, CI group. There was some disagreement between the reviewers on this diagnosis, although survival was similar whether the first or the second reviewer’s diagnosis was used [7]. The differences in survival between socioeconomic groups were essentially the same when cases on whom there was disagreement have been excluded from the analysis. The question can also be evaluated by limiting the analysis to the MI, CO, CT cases and those in the AP, CI group who had positive electrocardiographic findings. Survival of the MI, CO, CT group by occupation and education was presented in Table 4. Table 6 shows the age-adjusted per cent surviving 18 yr by findings of our review of the ECG
TABLE GROUP
6.
AGE-ADJUSTEDPERCENT OFPATIENTSSURVIVING~~ yr AFTERADMISSION BY SOCIOECONOMIC AND FINDINGS ON REVIEW OF ELECTROCARDIOGRAMS. WHITE MALES ALIVE 6 months AFTER ADMISSION WITH REVIEW DIAGNOSIS OF ANGINA PECTORIS OR CORONARY INSUFFICIENCY
Negative ECG Socioeconomic grouping*
Positive ECG
No ECG
% surviving
Total No.
% surviving
Total No.
% surviving
Total No.
Physician Other professional Non-professional All other
77.8 66.1 61.7 58.0
159 38 207 118
67.4 57.8 45.6 40.1
32 38 133 65
62.5 -
9 8 33 11
Total
66.1
522
49.4
268
65.6
61
*See text for definition of groups.
records and occupation for the AP, CI group. The prognosis is better for physicians than for the non-professional occupations, even among those with positive ECG findings, and the latter difference is sufficient to rule out fluctuations of sampling (p < 0.05). Among the 191 physicians whose ECG tracings were reviewed, fewer had positive findings (16.8 per cent) than among men in other occupations (39.1 per cent). The finding of a positive ECG in our review provides unbiased objective evidence of coronary disease. Information regarding occupation and education was not available in the part of the record containing the ECG tracings and it is unlikely that in our review the ECG’s of physicians were interpreted differently than those of other occupations. It therefore appears that a combination of factors produced the differences noted between the various socioeconomic groups, and they probably are not
888
Z. HRUBEC and W. J. ZUKEL
due entirely to differences in manifestations of the disease or inaccuracies of diagnosis. Rather, it seems plausible that among physicians, and to a lesser extent among the other professionals, the disease is detected at an earlier stage and better medical management is available to these groups in the follow-up period. If physicians are excluded from consideration, men with graduate education and those in professional occupations who completed college have slightly better prognoses than others. The latter differences are small but sufficient to demonstrate that probably they are not sampling artifacts. Reeder [14] reported that men in higher socioeconomic groups have a greater opportunity for modifying their working arrangements to accommodate to their cardiac disabilities. The latter information was obtained by interviewing 47 male cardiac patients and does not extend to survival. If the differential opportunities reported by Reeder do indeed exist in the general population, then in our study they account only partly for the differences in survival which also appear to be affected by differences in the clinical manifestations and in the intensity of detection of cases of coronary disease. Factors may be influencing our data which were not apparent in Reeder’s survey. About 90 per cent of these veterans had filed medical claims with the VA, but only about 25 per cent were receiving any disability compensation on 31 December 1957. The availability and quality of medical services for veterans may place them at an advantage in relation to nonveterans. However, despite a probable advantage with respect to medical care and a slightly higher socioeconomic status, veterans are by no means free of economic and occupational stresses [ 151. The large number of physicians included in the study may reflect higher rates of detection, possibly higher rates of incidence [16] and only to a limited extent the policies regarding their induction into military service. In the AP, CI group there undoubtedly are several times as many physicians as we would expect in a group of this size selected randomly from a military population. Their remarkably better prognosis may indicate that in other occupational and socioeconomic groups detection of early coronary heart disease is far from optimal. Even if education and occupation are held constant, Jewish men have a somewhat better prognosis than others. The difference could be an artifact particular to our sample, but more likely it is the result of social and medical factors that cannot be adequately explored in our material. We are not aware of studies which reveal that Jewish patients follow medical regimens more carefully than do non-Jewish patients. The predominance of Jewish subjects among the volunteers for the “Coronary Club” prevention program in New York City suggests that a motivational difference related to medical treatment may exist among Jewish subjects [17]. Marital status has been reported [6] to be associated with the prognosis of coronary heart disease. Our data are in agreement, but on a somewhat younger group of patients and on marital status defined before the coronary attack. It seems likely that married men find it easier to follow prescribed medical programs. Mortality from coronary heart disease and from all causes has been reported in other studies [18, 191 to be lower among groups with high socioeconomic status and among married persons. Gross mortality differences probably reflect differences in both incidence and prognosis. The present study is concerned only with prognosis and its findings are specific for narrow diagnostic and occupational groups. It is unlikely that they result from the same factors as affect total mortality.
Socioeconomic
Differentials in Prognosis following Episodes of Coronary Heart Disease
889
SUMMARY
Survival of first admissions to Army hospitals for coronary heart disease occurring from June 1943 to December 1944 was evaluated in a sample of 1495 white males who were alive 6 months after the date of admission. Included in this study are only cases whose hospital diagnosis was confirmed by an independent review of the history, laboratory data, and ECG recordings in their service medical records. Physicians were found to have a better prognosis than other occupations. When physicians were excluded, professional men with college education had a somewhat better survival than other occupation or education groupings. Physicians were more likely to have the diagnosis of angina pectoris or coronary insufficiency than others; however, their favorable prognosis was also found within diagnostic groups with specified ECG findings. The much better long-term survival of physicians may give some measure of the extent to which early detection and appropriate medical regimens can improve prognosis in coronary heart disease if followed by optimally motivated patients.
1. 2.
Amer J Med Sci 238: 297, 1959 Pell S, D’Alonzo CA: Acute myocardial infarction in a large industrial population. J Amer Med Ass 185: 831, 1963 Syme SL, Hyman MM, Enterline PE: Some social and cultural factors associated with the occurrence of coronary heart disease. J Cbron Dis 17: 277, 1964 Bernhard JS: Socioeconomic aspects of heart disease. J Educ Social 24: 450, 1951 Master AM: Survival and rehabilitation in coronary occlusion. Amer J Cardiol7: 340, 1961 Beard OW, Hipp HR, Robins M et al: Initial myocardial infarction among 503 veterans5-yr survival. Amer J Med 28: 871, 1960 Zukel WJ, Cohen BM, Mattingly TW et 4Z: following of heart Heart J 78: 159, Mantel tests with degree of freedom, of and
Indastries, Cemas of (Rev. ed.). D.C., 1950 Department of Bureau of Census: Methodology Scores of Status, Worklag No. 15. D.C., 1963 MM, White Simon R al: Long-term follow-up study of young coronary patients. Amer J Med Sci 247: 145, 1964 Honey GE, Truelove SC: Prognostic factors in myocardial infarction. Lancet 1: 1155, 1957 Pell S, D’Alonzo CA: Immediate mortality and 5-yr survival of employed men with a first myocardial infarction. New Eng J Med 270: 915, 1964 Rccder LG : The socioeconomic effects of heart disease. Sot Probl4: 51, 1956 Veterans Administration, Office of Controller, Reports and Statistics Service: Veterans in the United States, 1959; Employment, Income, Family, and Other Characteristics. Research Monograph No. 5, 1961 Dublin LI, Spiegelman M: The longevity and mortality of American physicians, 1938-1942. J Amer Med Ass 134: 1211,1947 Christakis G, Rinzler SH, Archer M et al: The anti-coronary club: A dietary approach to the prevention of coronary heart disease--a 7-yr report. Amer J Public Health 56: 299, 1966 Ellis JM: Socioeconomic Diierential in Mortality From Chronic Diseases. Patients, Physicians, and Illness. (E. Gartly Jaco, Ed). Glenco, Free Press, 1958 Kraus AS, Lilienfeld AM: Some epidemiologic aspects of the high mortality rate in the young widowed group. J Cbron Dii 10: 207, 1959
SOCIOECONOMIC DIFFERENTIALS IN PROGNOSIS FOLLOWING EPISODES OF CORONARY HEART DISEASE* Z. HRUBEC, Sc.D. Statistician,
Follow-up
Agency,
National Academy of Sciences-National Washington, D.C. 20418, U.S.A.
Research
Council,
Associate Director for Clinical Applications, National Heart and Lung Institute, National of Health, Bethesda, Maryland, U.S.A.
Institutes
and W. J. ZUKEL, M.D.
(Received 10 February 1970; in revised form 10 August 1970)
INTRODUCTION
between socioeconomic characteristics and the risk of developing coronary heart disease is well documented [l--4]. There are also numerous reports on clinical factors such as the severity of the initial attack, fever following the attack, and leucocytosis, which affect the prognosis of coronary heart disease after it develops [S, 61. However, very little has been reported on the relationship of socioeconomic characteristics to prognosis in this group of diseases. The purposes of this report are to present data on prognosis for men with various social and economic traits and to discuss the possible significance of the differences in prognosis for the management of the cardiac patient. THE ASSOCIATION
MATERIALS
AND
METHODS
A detailed description of the materials and methods of the study has been reported [7]. Information on survival and mortality was obtained from the files of the Veterans Administration for 2234 Army veterans who were admitted to service hospitals with first attacks of coronary heart disease between June 1943 and December 1944. *This work was carried out by the Follow-up Agency, National Academy of Science-National Research Council, 2101 Constitution Avenue, Washington, D.C. 20418, under contract number PH43-63-1139 with the National Heart Institute, National Institutes of Health, Bethesda Maryland. The investigation is part of a program of studies of the Follow-up Agency, developed by the Committee on Veterans Medical Problems and carried out in co-operation with the Veterans Administration, the Army, the Navy, and the National Institutes of Health. The conduct of this study depended on medical and other records of the Department of Defense, the Veterans Administration, and the National Archives and Records Service, GSA. We are indebted to these agencies, particularly to their records management personnel, for the ready access that they generously provided to the required material. We gratefully acknowledge the work of Bernard M. Cohen, Ph.D. (deceased 22 October 1962), in definition of the sample and preparation of the study materials, and the assistance of other staff of the Follow-up Agency: Mr. A. Hiram Simon, Chief of operations; Miss Vivian A. Heidenblut, the supervisor directly responsible for records abstracting and coding; and Mrs. Lucille P. Pogue for computational and analytic work. 881
Z. HRUBEC and W. J. ZUKEL
882
Various items of social, demographic, and economic information were obtained from the records of induction or enlistment into military service, and medical information was abstracted from the Army hospital records. Survival through 31 December 1962 was determined using the records of the Veterans Administration. A recent methodologic exploration indicated that the VA Master Index records the fact of death for 98 per cent of deceased white World War II veterans, regardless of prior medical history. To ensure the application of uniform diagnostic criteria two reviewers independently examined the medical information in the service records. There was some disagreement between them on the type of coronary heart disease but they both classified 68.4 per cent of the 2234 cases as belonging to this class of disorders [7]. The present work is based on the diagnoses of coronary heart disease made by only the first reviewer (W.J.Z.). Included here are 301 patients on whom there was disagreement about the presence of coronary heart disease. Of these latter patients 229 are considered in the present work as angina pectoris or coronary insufficiency and the remaining 72 are scattered in various diagnostic groups. The difference between the reviewers could have resulted from variation in the severity of signs or symptoms used for classification. In the work described here we thought it important to include the milder cases in order to maintain meaningful variability in prognosis. While the data presented reflect only one reviewer’s diagnoses we do evaluate relationships within groups of varying diagnostic certainty including ones based on objective electrocardiographic findings. We also analysed but do not present data on the group diagnosed as coronary heart disease by both reviewers since the results of that work are essentially redundant. Among the 1829 cases identified as coronary heart disease on the first review there TABLE 1. MEDIAN AGE AT ADMISSION AND NUMBEROF PATIENTSIN GROUPS BASEDON DIAGNOSIS,EDUCATION,AND OCCUPATION. WHITE MALESALIVE 6 months AFTERFIRSTADMISSION Median age at admission
No. with known age
Diagnosis :* MI, CO, CT AP, CI Other diagnosis
40.7 40.8
572 850 72
Education : Completed college Did not complete college
42.4 39.3
455 1039
41.7
248
43.1 38.2 48.9 38.9
230 769 164 83
40.3
1494t
Physicians and surgeons Other professional, technical. and kindred Not professional In service before 1941 Other Total *See text for explanation of abbreviations. tAge at admission was not known for one patient.
39.7
Socioeconomic
Differentials in Prognosis following Episodes of Coronary Heart Disease
883
were 105 nonwhite and 1724 white patients. The number of nonwhite patients is small and they have not been included in this analysis. In evaluating the significance of socioeconomic variables in prognosis it is useful to distinguish between the period of acute attack (lasting hours or days), the period of hospital convalescence (lasting weeks or months), and the period following discharge from the hospital. In the acute illness prognosis is related primarily to the clinical aspects of the disease. Since our present interest is primarily in long-term prognosis, most of the analyses have been based on the 1495 white Army veterans with a review diagnosis of coronary heart disease still alive 6 months after admission to the hospital. The median age of men with various characteristics is given in Table 1. The oldest patient was age 70, and 87 per cent of the men were less than 50 yr old at the time of the first admission. Therefore, most subjects were probably concerned with occupational adjustments to their disease. The median ages vary somewhat with occupation and education. Men completing college, physicians, and men in other professional, technical, and kindred occupations were older than the total group. Men in military service before 1941 were professional soldiers and were appreciably older. No meaningful differences in age were found between the three diagnostic groups of myocardial infarction, coronary occlusion, and coronary thrombosis (MI, CO, CT); angina pectoris and coronary insufficiency (AP, CI); and the other coronary diagnoses. Because of the age differences between various groups, age-adjusted percentages have generally been used in the analysis and their statistical significance was evaluated using tests described in reference 8. Unless specified otherwise, the age adjustment was direct and the weights used were derived from the age distribution of the total group of 1495 cases. RESULTS
Survival of men in different occupational groups is shown without age adjustment in Table 2. Occupations reported at entry into service are classified according to the 1950 census code of occupations [9]. The group of physicians and surgeons appears TABLET. PERCENTSURVIVING~~ yr AFTERADMISSION BYOCCUPATIONGROUP. WHITE MALES ALIVE 6 months AFTER ADMISSION WITH ANY DIAGNOSED CORONARY HEART DISEASE
Occupation group
Per cent
Total No.
Physicians and surgeons Other professional, technical, and kindred Managers and farmers Clerical and sales Operatives, craftsmen, foremen Personal service workers Laborers Stated, not classifiable In service before 1941 Students and unknown
71.9
249
48.3 44.4 48.5 54.3 41.8 58.1 54.7 34.8 50.0*
230 223 134 302 67 43 75 164 8
Total
51.7
1495
*Indicates that percentage is based on denominator
of 20 or less.
884
Z. HRUBEC and W. J. ZUKEL
to have a lower mortality than any other occupational grouping. The prognosis of men in service before 1941 seems less favorable, 34.8 per cent of them survived 18 yr. These men are appreciably older than men in other occupations. Their survival is comparable to that of the oldest age groups, but because of their extreme age distribution, adequate age adjustment is not possible. In the other groups, age adjustment of the per cent surviving 18 yr yields 71.6 per cent for physicians and surgeons, 50.3 per cent for other professional, technical, and kindred occupations, and 46.7 for all other occupations combined except men in service before 1941. TABLE 3.
AGE-ADJUSTEDPER
CENT*
SURVMNO BY years AFTER ADMISSION, OCCUPATION,AND p ADMISSION WITH ANY DIAQNOSED CORONARY HEART
EDUCATION. WI-IRE MALESALM? 6 months
DISEASE
Yr after admission Occupation
group
Physicians, surgeons Any except physicians, and surgeons Other professional, technical, and kindred Other professional, technical, and kindred Not professional, classifiable Not professional, classitiable All other Total
Highest educational level
No. alive at 6 months
5
10
15
18
Beyond college
94.4
86.7
75.2
71.9
249
Beyond college
89.9
74.9
59.9
54.8
87
College grad. only
91.5
75.8
63.4
58.1
62
< College grad.
86.3
69.2
57.4
49.6
88
College grad.
85.5
59.3
44.0
38.7
37
< College grad. AnY -
86.3 80.1 86.8
70.2 62.4 71.9
55.4 50.2 58.4
47.4 43.8 51.6
704 268 1495
*Adjusted to the age distribution
of the total group.
Table 3 presents age-adjusted survival by years after admission, educational level, and occupation. The usefulness of the U.S. Census classification in the scaling of occupations has been questioned [lo]. Admittedly the group designated as professional, technical, and kindred is very broad. To achieve greater specificity in the subsequent analysis and terminology, we have used the following socioeconomic groupings : (4 Physicians, including surgeons, not in service before 1941. (b) Other professional, including the 87 men with graduate education and the 62 in professional, technical and kindred occupations who completed college, not in service before 1941. (4 Non-professional, including those not in professional, technical and kindred occupations with less than graduate education and all those not completing college, not in service before 1941. (4 All not classified above. In the other professional group, those with graduate education were not differentiated by occupation. A detailed review of the individual codes indicated that only 19 of these patients were not coded as having a professional, technical or kindred occupation. Several of the latter involved questionable coding decisions such as inclusion of a ‘painter’ among craftsmen rather than artists. The better survival of physicians
Socioeconomic
Differentials
in Prognosis following Episodes of Coronary Heart Disease
885
over the other groups is again apparent in Table 3. The other professional group had a somewhat better prognosis than the non-professional (p < 0.05). The differences in survival among the various groups in Table 3 appear to be similar at different points throughout the 18-yr period. TABLE 4. AGE-ADJUSTED PER CENT SURVMNG SOCIOECONOMIC GROUP AND DIAGNOSIS. WHITE AFTER ADMISSION
18 yr AFTER ADMISSION BY MALES ALIVE AT 6 months
Diagnosis* MI, CO, CT
% Socioeconomic grouping*
AP, CI
%
surviving 18yr
Total No.
surviving 18yr
Total No.
Physician, surgeon Other professional Not professional, classified Other
50.6 50.2 32.7 35.2
45 56 325 146
77.4 62.3 55.7 53.9
200 84 313 194
Total
36.6
572
61.3
851
*See text for definition of groups.
Of the 1495 patients, there were 572 with the review diagnosis of MI, CO, CT and 851 with the review diagnosis of AP, CI. In Table 4 are presented adjusted 18-yr survival percentages by diagnosis and socioeconomic grouping. In the diagnostic group of AP, CI there was a considerable difference between the physicians and the other professional group (p < 0.05). In the diagnostic group of MI, CO, CT the difference was primarily between the physicians and other professionals compared to the non-professional group (p < 0.01). For both diagnostic groupings combined the other professionals had a better prognosis than the non-professionals (p < 0.05). The age-adjusted per cent surviving 18 yr was higher among Jewish patients (62.7 per cent) than among patients of other religious afhliation (50 .O per cent, p < 0.01). However, a fairly strong association exists among education, occupation, and religious affiliation. When crude survival percentages were compared separately for physicians and men in non-professional occupations without a college degree, Jewish patients again had a better prognosis in both groups (p c 0.05). Age adjustment of percentages within occupation groups was difficult because the data were considerably fragmented. To the extent that age adjustment was feasible within occupation groups, it seemed to reduce the apparent favorable prognosis of Jewish patients somewhat, and the differences could not be distinguished clearly from sampling fluctuations (~“0.10). Table 5 shows survival by marital status at entry into service and years after admission. Married men had favorable prognosis compared to single men (p < 0.05) or those who were divorced, separated, or widowed (p < 0.01) when an age-adjusted comparison was made. A similar relationship was seen within each of the two diagnostic groups.
HRUBECand W.
J. ZUKEL
TABLET. AGE-ADJUSTED PERCENTSURMVINGBYYEARSAFTERADMISSIONAND MARITALSTATUSATENTRYINTOSERVICE. WHITEMALESALI~E 6months ADMISSION
WITH
ANY
DIAGNOSED
CORONARY
HEART
Yr after admission
Married Single Divorced, separated Unknown
ARER
DISEASE
5
10
15
18
No. alive at 6 months
89.4 86.0
75.3 69.7
62.9 55.7
55.0 49.3
758 459
77.4 90.9
61.5 84.7
45.6 77.8
40.8 70.3
230 48
DISCUSSION
The appearance of differences in the survival of various socioeconomic groups following the diagnosis of coronary heart disease raises questions about the mechanisms which produced these findings. Do different disease processes go on in the various groups, is the disease detected at different stages, or are there differences in the medical regimens and stresses in the follow-up period? To what extent is the experience of this somewhat unusual sample of patients more generally applicable? The patients studied by us do not include the oldest ages which represent the bulk of many hospital series. Only survivors of the initial hospitalization have been included. The men have been screened through the military induction examination which eliminated those with obvious cardiovascular and other significant pathology. We are dealing with first episodes of the disease found in a setting in which the threshold of detection is low. The latter is reflected partly by the high proportion of cases diagnosed as angina pectoris or coronary insufficiency (56.9 per cent). In a comparably selected group of survivors of an initial episode of myocardial infarction uncomplicated by other cardiovascular or metabolic diseases and with a median age of 35 yr, Gertler et al, using life-table methods, estimated that 44.5 per cent of the patients were surviving 18 yr after diagnosis [ll]. Among our patients, the percentage surviving 18 yr with the review diagnosis of MI, CO, CT (adjusted to the age distribution of Gertler’s group) is 43.2 per cent. No reports on the survival of comparably selected groups of angina pectoris cases are known to us, but it seems reasonable that their experience should be better than that of the MI, CO, CT group. After age-adjusting to the ages of Gertler’s series, the 18-yr survival of our AP, CI patients is 68.4 per cent, considerably higher than the percentage for the MI, CO, CT group. Differences in the manifestation of coronary disease in the various socioeconomic groups could well result in differences in survival. According to evaluation of acute prognosis by others [2, 6, 12, 131 the determining factors are the nature of the acute attack and related clinical variables. Within diagnostic groups we found no appreciable association between mortality in the first 6 months and socioeconomic factors, but there were considerable differences between the various socioeconomic groups in the proportion of patients diagnosed as MI, CO, CT. Among physicians, 18.1 per cent were in that diagnostic group; among the other professional occupations, 37.6 per cent; and among men in non-professional occupations, 43.7 per cent.
Socioeconomic
Differentials
in Prognosis following Episodes of Coronary Heart Disease
887
Similarly, among Jewish patients 25.3 per cent were diagnosed with the more severe forms of coronary disease, while for the other religions, 39.7 per cent were so diagnosed. The differences with marital status are less remarkable, 36.4, 40.7, and 43.5 per cent, respectively, among married, single, and separated men. It therefore appears that the differentials in prognosis identified in our study are partly due to differences in the severity or manifestation of the disease at admission. The variation in the proportion of the MI, CO, CT diagnoses in various socioeconomic groups and the low mortality among the AP, CI case raise the possibility of different degrees of severity with socioeconomic traits or possibly differential admixture of patients free of coronary disease in the AP, CI group. There was some disagreement between the reviewers on this diagnosis, although survival was similar whether the first or the second reviewer’s diagnosis was used [7]. The differences in survival between socioeconomic groups were essentially the same when cases on whom there was disagreement have been excluded from the analysis. The question can also be evaluated by limiting the analysis to the MI, CO, CT cases and those in the AP, CI group who had positive electrocardiographic findings. Survival of the MI, CO, CT group by occupation and education was presented in Table 4. Table 6 shows the age-adjusted per cent surviving 18 yr by findings of our review of the ECG
TABLE GROUP
6.
AGE-ADJUSTEDPERCENT OFPATIENTSSURVIVING~~ yr AFTERADMISSION BY SOCIOECONOMIC AND FINDINGS ON REVIEW OF ELECTROCARDIOGRAMS. WHITE MALES ALIVE 6 months AFTER ADMISSION WITH REVIEW DIAGNOSIS OF ANGINA PECTORIS OR CORONARY INSUFFICIENCY
Negative ECG Socioeconomic grouping*
Positive ECG
No ECG
% surviving
Total No.
% surviving
Total No.
% surviving
Total No.
Physician Other professional Non-professional All other
77.8 66.1 61.7 58.0
159 38 207 118
67.4 57.8 45.6 40.1
32 38 133 65
62.5 -
9 8 33 11
Total
66.1
522
49.4
268
65.6
61
*See text for definition of groups.
records and occupation for the AP, CI group. The prognosis is better for physicians than for the non-professional occupations, even among those with positive ECG findings, and the latter difference is sufficient to rule out fluctuations of sampling (p < 0.05). Among the 191 physicians whose ECG tracings were reviewed, fewer had positive findings (16.8 per cent) than among men in other occupations (39.1 per cent). The finding of a positive ECG in our review provides unbiased objective evidence of coronary disease. Information regarding occupation and education was not available in the part of the record containing the ECG tracings and it is unlikely that in our review the ECG’s of physicians were interpreted differently than those of other occupations. It therefore appears that a combination of factors produced the differences noted between the various socioeconomic groups, and they probably are not
888
Z. HRUBEC and W. J. ZUKEL
due entirely to differences in manifestations of the disease or inaccuracies of diagnosis. Rather, it seems plausible that among physicians, and to a lesser extent among the other professionals, the disease is detected at an earlier stage and better medical management is available to these groups in the follow-up period. If physicians are excluded from consideration, men with graduate education and those in professional occupations who completed college have slightly better prognoses than others. The latter differences are small but sufficient to demonstrate that probably they are not sampling artifacts. Reeder [14] reported that men in higher socioeconomic groups have a greater opportunity for modifying their working arrangements to accommodate to their cardiac disabilities. The latter information was obtained by interviewing 47 male cardiac patients and does not extend to survival. If the differential opportunities reported by Reeder do indeed exist in the general population, then in our study they account only partly for the differences in survival which also appear to be affected by differences in the clinical manifestations and in the intensity of detection of cases of coronary disease. Factors may be influencing our data which were not apparent in Reeder’s survey. About 90 per cent of these veterans had filed medical claims with the VA, but only about 25 per cent were receiving any disability compensation on 31 December 1957. The availability and quality of medical services for veterans may place them at an advantage in relation to nonveterans. However, despite a probable advantage with respect to medical care and a slightly higher socioeconomic status, veterans are by no means free of economic and occupational stresses [ 151. The large number of physicians included in the study may reflect higher rates of detection, possibly higher rates of incidence [16] and only to a limited extent the policies regarding their induction into military service. In the AP, CI group there undoubtedly are several times as many physicians as we would expect in a group of this size selected randomly from a military population. Their remarkably better prognosis may indicate that in other occupational and socioeconomic groups detection of early coronary heart disease is far from optimal. Even if education and occupation are held constant, Jewish men have a somewhat better prognosis than others. The difference could be an artifact particular to our sample, but more likely it is the result of social and medical factors that cannot be adequately explored in our material. We are not aware of studies which reveal that Jewish patients follow medical regimens more carefully than do non-Jewish patients. The predominance of Jewish subjects among the volunteers for the “Coronary Club” prevention program in New York City suggests that a motivational difference related to medical treatment may exist among Jewish subjects [17]. Marital status has been reported [6] to be associated with the prognosis of coronary heart disease. Our data are in agreement, but on a somewhat younger group of patients and on marital status defined before the coronary attack. It seems likely that married men find it easier to follow prescribed medical programs. Mortality from coronary heart disease and from all causes has been reported in other studies [18, 191 to be lower among groups with high socioeconomic status and among married persons. Gross mortality differences probably reflect differences in both incidence and prognosis. The present study is concerned only with prognosis and its findings are specific for narrow diagnostic and occupational groups. It is unlikely that they result from the same factors as affect total mortality.
Socioeconomic
Differentials in Prognosis following Episodes of Coronary Heart Disease
889
SUMMARY
Survival of first admissions to Army hospitals for coronary heart disease occurring from June 1943 to December 1944 was evaluated in a sample of 1495 white males who were alive 6 months after the date of admission. Included in this study are only cases whose hospital diagnosis was confirmed by an independent review of the history, laboratory data, and ECG recordings in their service medical records. Physicians were found to have a better prognosis than other occupations. When physicians were excluded, professional men with college education had a somewhat better survival than other occupation or education groupings. Physicians were more likely to have the diagnosis of angina pectoris or coronary insufficiency than others; however, their favorable prognosis was also found within diagnostic groups with specified ECG findings. The much better long-term survival of physicians may give some measure of the extent to which early detection and appropriate medical regimens can improve prognosis in coronary heart disease if followed by optimally motivated patients.
1. 2.
Amer J Med Sci 238: 297, 1959 Pell S, D’Alonzo CA: Acute myocardial infarction in a large industrial population. J Amer Med Ass 185: 831, 1963 Syme SL, Hyman MM, Enterline PE: Some social and cultural factors associated with the occurrence of coronary heart disease. J Cbron Dis 17: 277, 1964 Bernhard JS: Socioeconomic aspects of heart disease. J Educ Social 24: 450, 1951 Master AM: Survival and rehabilitation in coronary occlusion. Amer J Cardiol7: 340, 1961 Beard OW, Hipp HR, Robins M et al: Initial myocardial infarction among 503 veterans5-yr survival. Amer J Med 28: 871, 1960 Zukel WJ, Cohen BM, Mattingly TW et 4Z: following of heart Heart J 78: 159, Mantel tests with degree of freedom, of and
Indastries, Cemas of (Rev. ed.). D.C., 1950 Department of Bureau of Census: Methodology Scores of Status, Worklag No. 15. D.C., 1963 MM, White Simon R al: Long-term follow-up study of young coronary patients. Amer J Med Sci 247: 145, 1964 Honey GE, Truelove SC: Prognostic factors in myocardial infarction. Lancet 1: 1155, 1957 Pell S, D’Alonzo CA: Immediate mortality and 5-yr survival of employed men with a first myocardial infarction. New Eng J Med 270: 915, 1964 Rccder LG : The socioeconomic effects of heart disease. Sot Probl4: 51, 1956 Veterans Administration, Office of Controller, Reports and Statistics Service: Veterans in the United States, 1959; Employment, Income, Family, and Other Characteristics. Research Monograph No. 5, 1961 Dublin LI, Spiegelman M: The longevity and mortality of American physicians, 1938-1942. J Amer Med Ass 134: 1211,1947 Christakis G, Rinzler SH, Archer M et al: The anti-coronary club: A dietary approach to the prevention of coronary heart disease--a 7-yr report. Amer J Public Health 56: 299, 1966 Ellis JM: Socioeconomic Diierential in Mortality From Chronic Diseases. Patients, Physicians, and Illness. (E. Gartly Jaco, Ed). Glenco, Free Press, 1958 Kraus AS, Lilienfeld AM: Some epidemiologic aspects of the high mortality rate in the young widowed group. J Cbron Dii 10: 207, 1959