1 University of Pittsburgh, Graduate School of Public Health, Department of Epidemiology, Pittsburgh PA.
2 National Center for Health Statistics, Department of Health and Human Services, Hyattsville, MD.
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ABSTRACT |
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cause of death; follow-up studies; men; mortality; occupations; sex ratio; women
Abbreviations: COPD, chronic obstructive pulmonary disease; CVD, cardiovascular disease; GS, General Schedule; NDI, National Death Index; SMR, standardized mortality ratio.
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INTRODUCTION |
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Concomitant with these changing trends in mortality, important changes have occurred in the social and economic roles of women. In particular, many women have moved into the labor force, occupying higher positions frequently held by men. As women increasingly assume multiple roles (e.g., worker, partner, parent), including the presumably demanding jobs formerly held predominantly by men, one question that arises is whether mortality rates will tend to equalize. Will women lose their survival advantage, or will the substantial income, freedom, and newly gained influence and self-esteem from higher-level paid work exert an additional positive influence on survival? Recent evidence would tend to suggest the latter, since women in either executive or professional positions have been found to have more favorable heart disease risk factors than do women who stay home (9, 10
). Moreover, some studies suggest enhanced psychologic well-being and health among women with concomitant employment and domestic roles (11
13
). Thus, to investigate this important public health issue, a search was conducted for an appropriate study population.
There are few occupations that allow for relatively unbiased comparison of men and women. One of these is the federal civil service. The higher civil service levelsGeneral Schedule (GS) 14 and above and their equivalentsare occupied primarily by managers and professionals with equal responsibility regardless of gender. These employees seemed to represent a suitable study population. Furthermore, by starting with those civil servants known to have been alive in December 1978, there was a mechanism in place for mortality follow-up by use of the National Death Index (NDI), which contains all deaths in the United States from 1979 onward.
This report compares the 15-year total and cause-specific mortality experience of 18,908 men and women in the US civil service who were rated as GS-14 and above or their equivalent. In addition, the mortality experience of this selected sample is compared with that of the general US population.
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MATERIALS AND METHODS |
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Occupationally, a supervisor was defined as a person who manages people and programs, whereas nonsupervisors are professionals such as physicians, scientists, and lawyers who do not supervise more than three people. Unfortunately, other desirable analytic variables (i.e., duration of employment, stress and decision latitude of job, smoking and other risk-related behaviors, medical history, family situation, etc.) were not available from this administrative data source. To obtain files for the study population, clearances were obtained from the Office of Work Force Information, Office of Personnel Management, and the National Institutes of Health Institutional Review Board for the Protection of Human Subjects.
NDI matching
Ascertainment of deaths was done by matching the study file against the NDI. This "passive surveillance" system has been shown to be about 95 percent complete (15). For a match against the NDI, each record submitted contained at least the first and last name and either the Social Security number or the month and year of birth. In addition to these required data elements, others such as sex and race were ascertained and included in the NDI search. The NDI Retrieval Program is designed such that, based on the number and type of matching data elements submitted in the search, a score is obtained that indicates the likelihood of a possible match (16
). The higher the score, the higher the likelihood of a match.
For study validation purposes, the distribution of scores was examined overall and in relation to subjects known to have died within 5 years of follow-up, as determined from an earlier NDI search. Among the early confirmed deaths, a matching score of 45 or more was found to have 100 percent specificity, whereas with a matching score less than 18, no subjects were confirmed to have died within 5 years. Therefore, death certificates were obtained for all subjects with a matching score of 18 or higher. This strategy maximized sensitivity for identifying all true deaths, but with the initial consequence of reduced specificity (false positives). Thus, careful inspection of each death certificate was performed to verify all true deaths and to identify false positives (persons not within the study population). With this approach, less than 1 percent of all death certificates received were subsequently deemed to be false positives. Causes of death were identified from the death certificates by a nosologist using International Classification of Diseases, Ninth Revision, codes.
Statistical methods
The probability of dying within 15 years for each 10-year age group from ages 3039 onward was calculated for men and women separately and by race (White vs. non-White). The denominators for the probabilities of the federal study population were the number of employees in each age group as of January 1, 1979, while the numerators were the number of deaths in each age group during the 15-year period from January 1, 1979 through December 31, 1993. Similarly, the number of cause-specific deaths in each age group was used in the numerators to calculate 15-year cause-specific mortality rates. Thus, cause-specific rates do not account for competing risks of mortality.
Age-adjusted, expected, 15-year total and cause-specific mortality rates by gender and race were obtained for three 5-year cohorts (19791983, 19841988, and 19891993) via the Internet from the Centers for Disease Control and Prevention WONDER Program (mortality database) (Centers for Disease Control and Prevention, Atlanta, Georgia). The three separate 5-year cohorts were used to account for changing trends in mortality in the United States during the 15-year follow-up period. The mortality data from the CDC WONDER Program were obtained in 10-year age groups overall and for specified International Classification of Diseases codes. From these data, hypothetical life tables were constructed for each cause of death by use of linear interpolation.
The 95 percent confidence intervals for the federal male/female mortality ratios were calculated, assuming the normal approximation to the binomial distribution (17). No confidence intervals for male/female mortality ratios were calculated for the general population because these are considered to be population values. Standardized mortality ratios (SMRs) using the general US population as the standard were calculated for men and women separately in 10-year age groups. The 95 percent confidence intervals for the SMRs were calculated based on the Poisson distribution (18
). Unconditional logistic regression analysis was used to estimate the risk of 15-year all-cause and cause-specific mortality in relation to age, gender, race, salary, and supervisor status. All p values are two-sided.
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RESULTS |
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Of the 18,669 participants (98.7 percent) with known race, 91.1 percent were White. Of the 1,670 non-White participants, 951 (56.9 percent) were African American, 337 (20.2 percent) were Asian, and the remaining 382 (22.9 percent) were of other races. Mortality data presented by race throughout are based on White and non-White groups only. The rationale for this was based on 1) insufficient numbers to stratify individual non-White races by gender; 2) nonsignificantly lower age- and gender-adjusted mortality in both African Americans and other non-White races compared with Whites; and 3) comparable age- and gender-adjusted mortality between African Americans and other non-White races.
Total mortality
During the 15-year follow-up (19791993), 1,614 deaths occurred, 1,304 of which were among men and 310 were among women (tables 1 and 2, column 3). The corresponding 15-year crude mortality rates for men and women were 9.2 and 6.6 percent, respectively. The 15-year US age-adjusted death rates and expected number of deaths among the federal managers and professionals are listed in tables 1 and 2, columns 5 and 6, respectively. At each age, both male and female federal workers experienced considerably lower mortality than did the US population at large, with the SMRs (column 7) being significantly less than 100 for all age groups of men and women.
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Among women in the federal cohort, the age-adjusted 15-year mortality was approximately 38 percent lower than that in the general population (SMR = 61.9, 95 percent confidence interval: 55.4, 69.2) (table 2). Unlike the pattern of mortality in men, the lower-than-expected mortality in women did not vary consistently by age. However, similar to men, the relative survival advantage experienced by women was particularly prominent among non-White subjects (SMR = 42.3, 95 percent confidence interval: 30.9, 57.9).
Table 3 provides the male/female 15-year mortality ratios by age and race for both the federal cohort and the US population. Among the federal managers and professionals, the crude male/female mortality ratio was 1.40, significantly less than the age-adjusted male/female ratio of 1.67 observed in the general US population. However, among study subjects aged 60 years or older in 1978, the 15-year male/female mortality ratio was virtually identical to that of the general US population (federal cohort = 1.55; general US population = 1.54).
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DISCUSSION |
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As one step in investigating these complex phenomena, we compared 15-year mortality rates between men and women in comparable high-level managerial and professional positions in the federal government in 1978. At these high job levels, it was found that women continue to experience lower mortality than do men at each age. However, the mortality ratio at ages 3069 years for men versus women was 1.40, significantly lower than the age-adjusted general US population ratio of 1.67. Notwithstanding possible self-selection bias between men and women into the federal cohort, this implies that, compared with the general population, women entering the predominantly male job roles of higher level civil service tend to decrease their relative mortality advantage and assume mortality rates more similar to those of men in these occupations. However, the fact that women continue to maintain a marked survival advantage over men within the confines of a very "low-risk" stratum (the federal employee cohort), with mortality nearly half that of the general population, suggests that employment alone is not responsible for the male/female disparity in mortality.
Findings similar to ours have been reported. Among US physicians, deaths in 19691973 for men, relative to the general male White population, were 75 percent of the expected deaths, whereas deaths for female physicians, relative to the general female White population, were 84 percent of the expected deaths, resulting in a decline in the male/female mortality ratio (19). Among professionals employed in Wisconsin, the sex mortality differentials for 19741978 were smaller in some age and marital status groups than those for the general population (20
). The above reductions in the female mortality advantage cannot be principally attributed merely to an advanced education level of higher-level employees, since the male/female mortality ratio among those with at least some college education has been shown to be similar to that of the general US population (21
). More recently, Baillargeon et al. (22
) reported a lower SMR among professional men (SMR = 0.64) compared with professional women (SMR = 0.79) hired for employment in a nuclear facility during the years 19441976.
Interestingly, the significantly lower-than-expected male/female mortality ratio in the federal employees disappeared among subjects aged 60 years and older at entry into the study. This may reflect, in part, the development and increasing predominance of chronic diseases with increasing age occurring in both men and women. Among nonelderly subjects (less than age 60 years), men experienced a greater reduction in expected mortality compared with women. In fact, the mortality experience among male federal employees was similar to the expected mortality experience of women in the general population. This may be because of the adoption of a healthy lifestyle in men, including reduced use of tobacco and heavy drinking, but this cannot be substantiated from our data. Moreover, it is possible that these higher-level civil service positions had lower exposure to occupational hazards, such as those in blue-collar occupations commonly filled by men. Sex differences in exposure to occupational hazards have been estimated to be responsible for roughly 510 percent of the sex differences in mortality, including roughly a fifth of the sex differences in fatalities from accidents (23).
Cause-specific mortality
Both men and women in the federal cohort experienced more than a 50 percent reduction in heart disease mortality compared with that expected from the general population. Thus, the approximate twofold heart disease mortality advantage traditionally enjoyed by women persisted in this study. Previous studies have reported inverse relations in both men and women between coronary heart disease and level of employment (2426
). Taken together, it appears that the sex differential in heart disease mortality is probably not modified by conditions associated with high-level employment (i.e., on-the-job stress).
A prominent study finding was the markedly lower-than-expected male/female cancer mortality ratio. Specifically, a more than twofold higher incidence of lung cancer mortality was expected in men, but a lower incidence was actually observed (male/female ratio = 0.80). This occurred primarily because men experienced more than a 60 percent lower lung cancer mortality than did the general population; women experienced lung cancer mortality similar to that of the general population. An intuitively appealing explanation would be lower rates of smoking in men, a hypothesis that cannot be investigated with our data. There is, however, supportive evidence for such an explanation. Although the prevalence of smoking is typically lower at higher levels of employment (2628
), women in executive and managerial positions may smoke more frequently and intensely compared with men in similar positions (26
) and with women in other job positions (29
30
31
). Thus, women may be more likely than men to use smoking as a stress modifier in response to the high demands and responsibilities of professional and managerial positions. The substantially lower-than-expected male/female COPD mortality ratio (0.83 observed vs. 1.82 expected) in this study is also consistent with the proposition of more frequent smoking in women. On the other hand, a presumed higher frequency of smoking in women would also be expected to reduce the male/female heart disease mortality ratio, a result not observed in this study.
Finally, another important observation was that non-Whites experienced the greatest improvement in survival relative to the general population and, in fact, fared nominally better than their White counterparts in the federal cohort. These data are largely consistent with previous reports (32, 33
), but are at odds with the unprecedented trend from 1984 through 1989 in which life expectancy generally decreased for both African-American men and women (34
). These data illustrate the strong association between high-level employment and survival and support previous evidence that minority ethnicity alone is not associated with higher mortality after controlling for socioeconomic status (35
). Still, it is possible that some persons may not experience similar survival from exposure to high-level employment, as indicated by the apparent elevated risk of cancer mortality observed among non-White female supervisors.
Limitations
The Federal Women's Study is a large cohort developed from administrative data files and follow-up for mortality by means of passive surveillance through the NDI. No effort could be made to contact any of the participants, and no data other than those in these files were available. Thus, the findings from this study have several limitations.
First, the lower-than-expected male/female mortality ratio may stem, at least in part, from self-selection (selection bias) into these jobs by men who may have been healthier, on average, than women at the time of hire. The men in the federal cohort are better educated, initially free of serious illnesses, and possibly less prone to hazardous health risk behaviors than is the general population. Women who enter the higher civil service ranks also share these characteristics, but perhaps to a more limited extent. As previously mentioned, men in managerial, administrative, and professional positions may be less likely to smoke than women of the same age in these positions (27, 32
). This suggests that more women than men in the current study may have been smokers at the time of entry into the study, which would tend to reduce the sex differential in mortality. Still, it is reasonable to assume that upon date of hire, both men and women equally enjoyed the implications associated with higher socioeconomic status, including universal access to high-quality health care.
A second issue concerns the comparison of the federal job roles with the general population. Undoubtedly, more men than women are exposed to hazardous jobs or lifestyles in the general population. Therefore, the favorable mortality experience of men in the higher-level government positions may reflect, in part, the reduction of exposure to these higher risks. On the other hand, the women in the high-level federal cohort occupy roles that, when compared with the general female workforce, tend to provide more stimulus, more control, and higher self-esteem. These factors would tend to enhance the "healthy worker effect" that is well established among both male and female employees (36) but has recently been suggested to be more pronounced in men than in women working in professional-level jobs (22
).
Third, the occupational history of study subjects, including duration of employment and exposure to specific job conditions, was unknown. If men experienced a longer duration of employment in the civil service or overall better job conditions than did women (i.e., more autonomy and job control), a more favorable relative improvement in their survival would be expected. However, if those with shorter duration of employment tended to find employment in other high-level jobs, as might be expected, then any differential duration of employment in the civil service between men and women would not be an appreciable source of confounding.
Finally, civil service employment is generally associated with long-term job stability, which would tend to counterbalance the potential adverse effect of stress associated with high-level job responsibilities. Thus, the results of this study may not generalize to high-level employment at large, such as within the private sector.
Conclusions
Our data suggest that employment in high-level occupations may have a differential impact on men and women. Both men and women in high-level jobs experience improved survival. However, the relative survival advantage experienced by women compared with men of the same age appears to be less prominent at higher levels of employment. This appears to be largely a result of an overall lack of improvement in cancer mortality (especially lung cancer) for women. The male/female ratio of heart disease mortality does not appear to be altered by exposure to high-level employment.
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ACKNOWLEDGMENTS |
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NOTES |
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REFERENCES |
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