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Association of self-reported religiosity and mortality in industrial employees: the CORDIS study
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Social Science & Medicine 58 (2004) 595–602
Association of self-reported religiosity and mortality in industrial employees: the CORDIS study Allen Krauta, Samuel Melamedb,c,*, Daphna Goferb, Paul Froomb,c b
a Departments of Internal Medicine and Community Health Sciences, University of Manitoba, Winnipeg, Canada National Institute of Occupational & Environmental Health, Department of Occupational Health Psychology, P.O. Box 3, Raanana 43100, Israel c Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
Abstract This study examined the association between self-reported religiosity and mortality in industrial employees, while controlling for workplace and socioeconomic factors. Subjects were 3638 Jewish Israeli males who participated in a 12year follow-up study. During this period 253 deaths were recorded. The prevalence of negative workplace and sociodemographic factors: lower education, non-European origin, heavy physical work, blue-collar jobs and adverse job and environmental conditions, was highest among religious employees, and lower in traditional and nonreligious employees in descending order. Using Cox’s proportionate hazard model an age by religiosity interaction on mortality was uncovered. In younger employees (age o55 years) religiosity was associated with lower adjusted mortality, after controlling for negative workplace and sociodemographic factors. Compared with nonreligious employees, the hazard ratios for the religious and traditional employees were: 0.64 (p ¼ 0:016) and 0.39 (p ¼ 0:118), respectively. In older employees (age X55 years), religiosity was associated with higher adjusted mortality. The corresponding hazards ratios were 1.69 (p ¼ 0:011) and 1.08 (p ¼ 0:004), even after controlling for the above possible confounding variables. It was concluded that religiosity had a protective effect on mortality in younger employees, but the reverse was true for older employees. This opposite trend could not be explained by negative sociodemographic and workplace conditions. The possibility of involvement of yet another potent factor of social isolation was discussed. r 2003 Elsevier Ltd. All rights reserved. Keywords: Mortality; Religiosity; Blue collar; Employees; Industrial
Introduction The putative association between religion and health status has been studied for over a century (Galton, 1872). Religious attendance has been associated with a decrease in overall mortality (Oman & Reed, 1998; Koenig et al., 1999; Hummer, Rogers, Nam, & Ellison, 1999; McCullough, Hoyt, Larson, Koenig, & Thoresen, 2000; Strawbridge, Cohen, Shema, & Kaplan, 1997; *Corresponding author. National Institute of Occupational & Environmental Health, Department of Occupational Health Psychology, P.O. Box 3, Raanana 43100, Israel. Tel.: +972-9771-0094; fax: +972-9-771-2212. E-mail address: [email protected] (S. Melamed).
Goldbourt, Yaari, & Medalie, 1993). In a study of older California residents, Oman and Reed (1998) found that those who reported attending religious services had a lower mortality (age and sex adjusted relative hazard 0.64; 95% confidence intervals (CI) 0.52, 0.78) than those who did not. This relationship held true even after adjustment for health status, physical function, and social support. Similar results were reported in older community dwelling adults in North Carolina (Koenig et al., 1999) and in individuals residing in Alameda County, California (Strawbridge et al., 1997). Further support was provided by a study in civil servants (Goldbourt et al., 1993). Hummer et al. (1999) modeled the association of religious attendance with overall and cause-specific mortality using data from the National
0277-9536/03/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0277-9536(03)00282-X
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Health Interview Survey—Multiple Cause of Death linked file. They noted an inverse relationship after controlling for demographic, and certain health, socioeconomic, and social variables. Although the strength of the association varied by cause of death, its direction remained consistent across causes (Hummer et al., 1999). All of these authors recognized that the physical ability to attend religious services might have influenced their findings, but they did not believe it served as a confounding factor in the observed relationship. Studies that have used private measures of religious observance, such as praying at home or self-described religiosity, reported conflicting results with respect to mortality. Some found either no association with allcause mortality (Krause, 1998; Helm, Hays, Flint, Koenig, & Blazer, 2000) or decreased mortality only in subsets without impairments in activities of daily living (Helm et al., 2000). In Israel, a community study in Jerusalem yielded no association between religiosity and total mortality in men aged 60 years or older (Abramson, Gofin, & Peritz, 1982), whereas a kibbutz-based study found higher mortality on secular than on religious kibbutzim (rate ratio 1.93; 95% CI 1.44, 2.59) (Kark et al., 1996). In the latter work, there were no differences by sex, age, or cause of death, and the findings were consistent throughout the 16-year observation period. However, the authors failed to control for traditional risk factors. In studies of cancer patients, self-reported religiosity was identified as a protective factor for the development of colorectal cancer (Kune, Kune, & Watson, 1993), but it did not influence cancer mortality (Kune et al., 1993; Loprinzi et al., 1994). A more recent meta-analysis suggested that the association between religious involvement and mortality is modest (odds ratio 0.78; 95% CI 0.72–0.83) (McCullough et al., 2000). The positive effects of religion on health may be mediated through a number of tentative mechanisms. Individuals with strong religious faith report higher levels of life satisfaction, greater personal happiness, and fewer negative psychosocial consequences of traumatic life events (Ellison, 1991). Religious observance has also been associated with increased social support (Friedlander, Kark, Kaufmann, & Stein, 1985), more stable marriages (Kark et al., 1996; Strawbridge et al., 1997), and less involvement in risky behaviors (Waite, Hawks, & Gast, 1999; Hammermeister, Flint, Havens, & Peterson, 2001). Indeed, Kark et al. (1996) proposed that the contribution of religious observance to the creation of a less stressful environment could explain the mortality differences they found between the secular and religious kibbutzim. Differences in conventional risk factors have also been implicated: religious observance has been associated with lower smoking rates (Strawbridge et al., 1997; Friedlander et al., 1985), and a more protective plasma lipid and lipoprotein
profile (Friedlander et al., 1985; Friedlander, Kark, & Stein, 1987). It is noteworthy that the studies cited so far were performed in the community, and there is almost no research into the potential protective effect of religiosity on mortality in industrial employees. The majority of industrial employees (usually 60–70%) are blue-collar workers. It is well documented that blue-collar workers are exposed to a variety of concurrent adverse job and environmental conditions, such as safety hazards, physico-chemical agents, and psychosocial stressors (Anderson & Fletcher, 1979; Melamed, Yekutieli, Froom, Kristal-Boneh, & Ribak, 1999). They may also have poorer health habits and less access to good health care than white-collar workers (McMichael & Hartshorne, 1982; Naslund, 1997; Burton & Turrell, 2000; Korda, Strazdins, Broom, & Lim, 2002). While some studies found no difference in mortality rate by occupational status (e.g., Costa, Merletti, & Segnan, 1989), many others reported higher total and causespecific mortality (e.g., cancer, coronary heart disease, cerebrovascular disease) in blue-collar than in whitecollar workers (McMichael & Hartshorne, 1982; Aro & Hasan, 1987; Buring, Evans, Fiore, Rosner, & Hennekous, 1987). Thus, it is plausible that in industrial employees, the protective effect of religiosity may be masked by exposure to health-damaging factors in the work environment. The objective of this study was to determine whether self-reported religiosity is associated with overall mortality in Israeli industrial (mainly blue-collar) workers.
Subjects and methods Study population The original study population consisted of the 3816 Jewish men who participated in the Cardiovascular Occupational Risk Factors Determination in Israel Study (CORDIS) in 1985–1987 (Froom, Melamed, Kristal-Boneh, Gofer, & Ribak, 1996; Froom, Melamed, Kristal-Boneh, Benbassat, & Ribak, 1999; Melamed et al., 1999; Kristal-Boneh, Harari, Melamed, & Froom, 2000). The subjects were recruited from 21 industrial plants (metal work, textiles, light industry, electronics, food manufacturing and plywood production) throughout Israel for on-site screening of cardiovascular risk factors. They represented approximately 69% of the workforce at these sites. The study participants were found to be healthier, older, and less likely to be employed in large factories than the nonparticipants (Froom et al., 1999). At the time of the initial evaluation, information was collected on a variety of workplace and personal factors, and routine blood tests, an electrocardiogram, and a brief physical
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examination were performed. Testing was done at a rate of one or two plants per month until the entire sample was collected. One hundred and sixty-seven men were excluded from the analysis because of missing values. Data on mortality in the study group from 1987 to 1998 were obtained from the National Death Registry of the Israel Ministry of the Interior using the workers’ identity numbers that were obtained from the factory records and verified during the initial examination. Verification was obtained for all but 21 men (see Froom et al., 1999). Thus, this study was based on 3628 individuals and 42,322 person-years of follow-up. Results showed that 253 study participants died (7.0%) over the 12-year period. Level of religious observance At the interview, employees were asked their level of religiosity and were categorized into three groups on the basis of the findings: religious—individuals who strictly observed Jewish law; traditional—individuals who maintained the traditions of the faith but were more moderate and flexible in their observance than religious workers; and nonreligious. Self-reported religiosity has been used as part of or the entire defining variable (Friedlander et al., 1985; Friedlander, Kark, & Stein, 1986; Friedlander et al., 1987; Goldbourt et al., 1993) in other studies on religion and health in Israel, with a high concordance with questions measuring the degree of religious observance (Friedlander et al., 1987). The Spearman correlation coefficient between self-perception of religiosity and self-reported degree of observance of religious rules was 0.88. The correlation was 0.80 for an additional four-point religiosity scale based on the answers to questions about observance of specific rules and self-reported religiosity. Potential confounding variables Sociodemographic Potential sociodemographic confounders included age, educational level (more or less than 12 years), marital status, and ethnicity (country of origin of the father was used as a surrogate for ethnicity). Individuals were identified as North African, Asian or European if they could trace their ancestry to these areas. Those of African and Asian ancestry (Sephardic Jews) were grouped together, and those of European origin (Ashkenazi Jews) were analyzed separately. Occupational The industrial employees were broadly classified into white collar and blue collar. A blue-collar worker was defined as belonging to one of the following job categories: (a) direct production, (b) indirect production, (c) maintenance, (d) housekeeping, transportation,
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(e) first-line supervisor, foreman, (f) shift foreman, and (g) unclassified manual worker. All other employees were considered white collar. Managers and employees within each category were identified. As part of the CORDIS study, a comprehensive ergonomic evaluation was done of the work and environmental conditions at the workstations of each of the study participants (see Melamed et al., 1999). The 62-item Ergonomic Stress Inventory was used to collect data on 17 risk factors pertaining to safety hazards, overcrowding, cognitive and physical demands, and environmental stressors (for more details see Melamed et al., 1999). The internal consistency coefficient of the inventory was 0.95. Each participant was assigned a global ergonomic stress level (ESL) score, from 1 to 4, which was based on his average score across the 62 items of the inventory. The ESL was found to be a stable measure over a period of 2–4 years. In view of the threshold effect on association with injury risk (Melamed et al., 1999), scores 1 and 2 and scores 3 and 4 were combined to form two levels: low-ESL job and high-ESL job. Physical workload, which has been shown to predict mortality in this cohort (Kristal-Boneh et al., 2000), was abstracted from the workers’ subjective ratings. The ratings were made on a 4-point scale and then collapsed to two levels: no or light workload and moderate or high workload (Kristal-Boneh et al., 2000).
Statistical analysis The significance of differences between groups was tested as follows: t-test or one-way analysis of variance was applied for continuous variables, and w2 test for categorical variables. Cox’s proportional hazard regression model controlling for time was used to test whether the study groups differed in adjusted mortality rates when controlling for potential confounding variables. Two models were used: the first was adjusted only for age, and the second was adjusted for age and for the other sociodemographic and occupational factors evaluated in the study. In an additional step, we included the cross-products of religiosity and each of the control variables in the model in order to examine the effect of their interaction on mortality. Only age religiosity proved to have a significant effect. Therefore, the sample was further stratified by age (more or less than 55 years) in order to examine the association between religiosity and mortality within each stratum. All data were analyzed with SAS version 6.12. The reported measure of association was the hazard ratio (HR) with 95% confidence limits (95% CI), with the nonreligious employees serving as the comparison
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group. A p value of 0.05 was set as the level of significance.
Results The individuals excluded from the analysis because of missing data did not differ from the rest of the cohort by age, mortality, religiosity, national origin, smoking status, and performance of moderate or physical workload. Table 1 details the sociodemographic and occupational characteristics of the religious, traditional, and nonreligious groups. Compared to the nonreligious workers, the religious workers were older, more likely to be married, less likely to be of European origin, and less educated. A greater proportion were blue-collar workers. Their jobs were more physically strenuous jobs than those of the nonreligious workers and had a higher ESL, which signifies exposure to adverse work and environmental conditions. The differences for all these factors were statistically significant. Overall, the data showed a trend for several negative sociodemographic and occupational parameters associated with religiosity in descending order across the three study groups. Results of the proportionate hazard models are presented in Table 2. Analyses adjusted only for age (model 1) revealed higher all-cause mortality HRs in the religious and traditional groups than the nonreligious. When we adjusted for sociodemographic and workplace factors (model 2), the mortality HRs decreased and became nonsignificant. As noted in the Methods section, there was a significant interactive effect of age and religiosity on mortality (p for trend=0.02). Therefore, the study sample was stratified into younger (o55 years) and older employees. We then repeated the analysis presented in Table 1 for the younger and older groups separately to determine any possible differences in
sociodemographic and workplace characteristics between them. The results are presented in Table 3. Compared with the younger workers, the older group had a higher proportion of religious individuals and of individuals of non-European origin, and fewer years of education. They also had greater exposure to negative occupational factors, namely, high physical workload, blue-collar jobs, and high-ESL jobs. These findings indicate that there is an important difference between these two age groups that needs to be controlled for in further analyses. The results of the proportional hazard models applied to the younger and older employees are given in Table 4. The models were adjusted for the same variables as in the total-sample analysis. Different trends were found in the association between religiosity and mortality by age. In the younger group, adjusting only for age (model 1) yielded no significant association of religiosity with mortality. However, when we adjusted for all the sociodemographic and workplace variables (model 2), there was an association of religiosity with lower mortality, which reached a significant level in the religious group (HR=0.39, 95% CI 0.18–0.84) and trend level (but not statistically significant) in the traditional employees (HR=0.84, 95% CI 0.37–1.12). By contrast, in the older employees, religiosity was associated with increased adjusted mortality in both models. Thus, the trend in model 1 remained consistent even after controlling for all the potential confounders. The corresponding HRs in model 2 were 1.69 (95% CI 1.13–2.52) for the religious group and 1.99 (95% CI 1.23–3.10) for the traditional group.
Discussion The first major finding of this large cohort study of industrial employees was that for the total sample, the more religious group did not have a lower mortality rate
Table 1 Comparisons of sociodemographic and work factors among religious, traditional and non-religious members of the CORDIS data set (1985–1987)a Variable
Religious
Traditional
Non-religious
p value
Number Age, years Education o12 years Married European origin Blue-collar jobs Moderate or intense physical workload High-ESL jobs
694 47.2711.5 553 (79.7%) 649 (93.5%) 167 (24.1%) 627 (90.3%) 537 (77.4%) 484 (69.7%)
1512 44.4712.0 1044 (69.1%) 1358 (89.8%) 503 (33.3%) 1239 (81.9%) 1029 (68.1%) 999 (66.1%)
1422 44.4711.5 622 (43.7%) 1253 (88.1%) 1081 (76.0%) 894 (62.9%) 659 (46.3%) 718 (50.5%)
0.0001 0.001 0.001 0.001 0.001 0.001 0.001
ESL, ergonomic stress level. a Means and standard deviations are given for continuous variables; n and percentages are given for categorical variables.
ARTICLE IN PRESS A. Kraut et al. / Social Science & Medicine 58 (2004) 595–602 Table 2 Influence of self reported religiosity on all cause mortality: results of a proportional hazard regression (Cox) model Hazard ratio
95% CI
p value
Model 1 Age Non-religious Traditional Religious
1.10 1.00 1.40 1.55
1.09–1.12 — 1.04–1.87 1.11–2.15
0.0001 — 0.026 0.009
Model 2 Age Non-religious Traditional Religious Blue-collar jobs Physical workload High-ESL jobs Education o12 years Non-European origin Not married
1.11 1.00 1.20 1.21 0.92 1.48 1.04 1.35 1.13 1.25
1.10–1.12 — 0.82–1.77 0.87–1.65 0.60–1.40 1.05–2.07 0.77–1.41 0.96–1.89 0.84–1.52 0.76–2.05
0.0001 — 0.273 0.338 0.685 0.026 0.781 0.084 0.414 0.382
ESL, ergonomic stress level; CI, confidence interval.
Table 3 Comparison of some sociodemographic and workplace factors in younger (o55 years) and older employees (X55 years) in the CORDIS data set (1985–1987)a Variable
Age o55 years
Age X55 years
Number Age, years Non-religious Traditional Religious Education o12 years European origin Married Moderate or intense physical workload Blue-collar jobs High-ESL jobs Job tenure, years
2676 39.578.4 1082 (40.4%) 1131 (42.3%) 463 (17.3%) 1521 (56.8%)
952 60.174.3 340 (35.7%) 381 (40.2%) 231 (24.3%) 698 (73.3%)
0.001
1482 (55.4%) 905 (95%) 1592 (59.5%)
395 (41.5%) 2355 (88%) 633 (66.5%)
0.001 0.005 0.001
2006 (75.0%) 1587 (59.3%) 8.577.4
754 (79.2%) 614 (64.5%) 14.779.8
0.008 0.005 0.0001
p value
0.0001
ESL, ergonomic stress level. a Means and standard deviations are given for continuous variables; n and percentages are given for categorical variables.
than the nonreligious control group. This contradicts the findings of some community studies (Strawbridge et al., 1997; Oman & Reed, 1998; Koenig et al., 1999; Hummer et al., 1999; McCullough et al., 2000) and the study of white-collar employees (Goldbourt et al., 1993). Indeed, when we adjusted only for age, but not for
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workplace and sociodemographic factors, mortality was high in both the religious and the traditional employees. The corresponding HRs were 1.55 (95% CI, 1.11–2.15) and 1.40 (95% CI, 1.04–1.87) compared with the nonreligious employees. However, this difference was no longer significant (HR=1.21[0.87–1.65] and HR=1.20 [0.82–1.27], respectively) after adjusting for the other factors, namely, blue-collar work, heavy physical workload, adverse job and environmental conditions (high ESL job), lower education, and single status. A similar lack of association between religiosity and all-cause mortality was obtained in the community studies in which the various potential confounding variables were controlled for (Krause, 1998; Helm et al., 2000). An additional noteworthy finding pertaining to the total sample was the nearly linear association between religiosity and negative workplace and sociodemographic factors (see Table 1). A clear trend was noted when the religious and traditional groups were compared with the nonreligious employees. The former two groups were older, had a lower level of education, were less likely to be of European origin, performed more strenuous physical work, held more blue-collar jobs, and were exposed to worse job and environmental conditions (higher ESL). These parameters were most prevalent in the religious group. Thus, in this cohort of industrial employees, religiosity turned out to be a proxy of negative work and sociodemographic factors. Given the association between blue-collar work and increased mortality (see Introduction for review), it becomes clear why, in the present sample of industrial employees, religiosity was associated with increased mortality, and not the reverse. Further studies are needed to determine if these findings can be generalized to other populations of industrial employees. The second major finding of the present study was the interaction of the association between religiosity and mortality with age. Two opposite trends were uncovered by stratifying the total sample into younger (o55 years) and older (X55 years) employees. The protective effect of religiosity was observed only among the younger employees, and it became significant for the religious employees (HR=0.39, 0.18–0.84) only after adjusting for work and sociodemographic factors (see Table 4). The protective effect of religiosity was also observed among the traditional employees, but it did not reach statistical significance (HR=0.64, 0.37–1.12). These findings are important for two reasons: they show that the same protective effect of religiosity previously observed in community samples also holds true for younger industrial employees; and they show that the beneficial effect of religiosity is significant only for religious and not for traditional employees. By contrast, in the older employees, religiosity was associated with elevated mortality, even after adjusting
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Table 4 Influence of age stratification on the association of self-reported religiosity with all-cause mortality: results of a proportional hazard regression (Cox) model Age o55 years
Model 1 Age Non-religious Traditional Religious Model 2 Age Non-religious Traditional Religious Blue-collar job Physical work High ESL job Education o12 years Non-European origin Not married Number of deaths
Age X55 years
Hazard ratio
95% CI
p value
Hazard ratio
95% CI
p value
1.12 1.00 0.93 0.61
1.09–1.16 — 0.58–1.51 0.31–1.21
0.0001 — 0.1592 0.7775
1.07 1.00 1.77 2.17
1.04–1.11 — 1.21–2.58 1.44–3.25
0.0001 — 0.003 0.0002
1.12 1.00 0.64 0.39 0.90 1.11 1.17 1.85 1.47 1.15
1.08–1.15 — 0.37–1.12 0.18–0.84 0.43–1.87 0.61–2.01 0.66–2.08 1.01–3.39 0.85–2.52 0.46–2.91 78
0.0001 — 0.1188 0.0163 0.7752 0.7280 0.5820 0.0465 0.1650 0.7632
1.08 1.00 1.69 1.95 0.94 1.67 0.97 1.10 0.99 1.40
1.04–1.12 — 1.13–2.52 1.23–3.10 0.56–1.83 1.10–2.53 0.68–1.38 0.70–2.18 0.70–1.40 0.78–2.62 175
0.0001 — 0.011 0.004 0.819 0.017 0.855 0.652 0.935 0.265
for work and sociodemographic factors. This finding was significant in both the religious and the traditional groups (HR=1.69, 1.13–2.52 and HR=1.95, 1.23–3.10, respectively). In our initial analysis of the total sample, the excess mortality among the traditional and religious groups disappeared after adjusting for work and sociodemographic factors. On further analysis, this finding proved to be due to the inclusion of the younger employees in the total sample. For the younger employees, adjusting for these factors uncovered a protective effect of religiosity. The data here show that older employees, in general, have worse job status and worse work and environmental conditions than younger employees (Table 3). They also have significantly longer job tenure and lesser education. Thus, it seems that older employees have fewer options for mobility within the organization and less possibility to change undesirable job and environmental conditions. This may result in long exposure to negative agents that may have a cumulative and adverse effect on their health. Nevertheless, the elevated mortality in the older traditional and religious employees remained significant even after controlling for these potential confounding factors. This suggests that the elevated mortality was due to a factor or factors other than the job and environmental characteristics measured. One potentially powerful factor that was not systematically measured in the data-collection phase of the study, but which may partly account for the interaction of religiosity and age on total mortality, is lack of social
integration (social isolation and lack of social support) at work. There is sufficient evidence indicating that social isolation/lack of social integration is associated with increased total and cause-specific mortality (e.g., Olsen, 1993; Siahpush & Singh, 1999; Eng, Rimm, Fitzmaurice, & Kawachi, 2002). There is also more specific evidence showing that social ties and social support at work protect against total or cause-specific mortality (Johnson, Hall, & Theorell, 1989; Hibbard & Pope, 1992). In the study of Johnson et al. (1989) of the Swedish male working population, the groups showing the greatest risk of both morbidity and mortality were blue-collar employees working under highly isolated and strained conditions. In post-study interviews with the subjects in our cohort, we discovered that the religious and traditional employees tended to seek out peers at work with similar religiosity. If there were few such candidates in their immediate work environment, the older employees felt fairly isolated, whereas the younger ones were more likely to form social ties with their nonreligious co-workers instead. This difference may stem from the fact that 49% of the younger religious/ traditional employees were either born in Israel or immigrated before the age of 10 compared to only 4.7% of their older counterparts. Therefore, though both groups were exposed to adverse job and environmental conditions, the younger group may have had more access to the coping resource of social support. More systematic studies measuring social support at work are warranted to verify this casual observation. Other psychosocial factors need to be measured as well to
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explain our novel finding of an interaction between religiosity and age on total morbidity. An alternative explanation for the increased mortality among the older members of the cohort is the presence of a systematic selection bias. The CORDIS cohort was comprised of individuals who were healthier than the general population (standardized mortality ratio 71; 95% CI 60–83) owing to a combination of healthy worker and volunteer effects (Froom et al., 1999). It is possible, however, that these effects were selective, such that the older religious employees who were ill had no alternative but to remain in the workforce. A theoretical limitation of the study is our definition of religious involvement. The appropriateness of self-reported religiosity as a measure of religious involvement has been questioned by some authors (McCullough et al., 2000) as it may not truly measure religious commitment. Nonetheless, this is unlikely to have affected our study, because lines of religious involvement in Israel are not blurred. The vast majority of the self-reported religious Israeli Jews who took part in CORDIS were Orthodox. Furthermore, other studies conducted in Israel on the association of religion and health based their findings on self-reported religiosity (Goldbourt et al., 1993; Friedlander et al., 1985, 1986, 1987). Friedlander et al. (1987) reported a high concordance of self-reported religiosity with questions that measured the degree of religious observance. In our work, the validity of the religiosity measurement was reinforced by the finding that at least in the younger employees, the significant association between religiosity and mortality was in the direction observed in previous studies. Thus, we are confident that our definition of religiosity properly identified individuals with a religious commitment.
Conclusion This cohort study showed for the first time that the same protective effect of religion against mortality found in community samples and white-collar employees is also true for younger (o55 years) industrial employees. Both the younger and older (X55 years) religious/traditional employees in our study were predominantly blue-collar workers with lower education and higher exposure to adverse job and environmental conditions than their nonreligious counterparts. These sociodemographic and workplace factors were previously shown to be associated with elevated total and cause-specific mortality. Indeed, only after we controlled for them did we uncover the protective effect of religiosity in the younger employees. By contrast, in the older employees, religiosity was associated with elevated mortality in both the religious and traditional groups, even after controlling for the potent
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confounding variables listed above. This persistence of elevated mortality in the older group suggests that other, as yet unidentified factors, may be at play. However, our casual observation made after the completion of the study indicates that older religious employees are more socially isolated at work than younger ones and may therefore lack the important buffering resource of social support. Further studies of industrial employees are needed to replicate our findings and to determine the reason underlying the interaction of religious observance with age on total mortality.
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Galton, F. (1872). Statistical inquiries into the efficacy of prayer. Fortnightly Review, 12, 125–135. Goldbourt, U., Yaari, S., & Medalie, J. H. (1993). Factors predictive of long-term coronary heart disease mortality among 10,059 male Israeli civil servants and municipal employees. A 23-year mortality follow-up in the Israeli Ischemic Heart Disease Study. Cardiology, 82, 100–121. Hammermeister, J., Flint, M., Havens, J., & Peterson, M. (2001). Psychosocial and health-related characteristics of religious well-being. Psychological Reports, 89, 589–594. Helm, H. M., Hays, J. C., Flint, E. P., Koenig, H. G., & Blazer, D. G. (2000). Does private religious activity prolong survival? A six-year follow-up study of 3851 older adults. The Journals of Gerontology, Series A Biological Sciences and Medical Sciences, 55, M400–M405. Hibbard, J. H., & Pope, C. R. (1992). Women’s employment, social support, and mortality. Women and Health, 18, 119–123. Hummer, R. A., Rogers, R. G., Nam, C. B., & Ellison, C. G. (1999). Religious involvement and US adult mortality. Demography, 36, 273–285. Johnson, J. V., Hall, E. M., & Theorell, T. (1989). Combined effects of job strain and social isolation on cardiovascular disease and mortality in a random sample of the Swedish male working population. Scandinavian Journal of Work Environment and Health, 15, 271–279. Kark, J. D., Shemi, G., Friedlander, Y., Martin, O., Manor, O., & Blondheim, S. H. (1996). Does religious observance promote health? Mortality in secular vs religious kibbutzim in Israel. American Journal of Public Health, 86, 341–346. Koenig, H. G., Hays, J. C., Larson, D. B., George, L. K., Cohen, H. J., McCullough, M. E., Meador, K. G., & Blazer, D. G. (1999). Does religious attendance prolong survival? A six-year follow-up study of 3968 older adults. The Journals of Gerontology, Series A Biological Sciences and Medical Sciences, 54, M370–M376. Korda, R. J., Strazdins, L., Broom, D. H., & Lim, L. L. (2002). The health of the Australian workforce: 1998–2001. Australian and New Zealand Journal of Public Health, 26, 325–331. Krause, N. (1998). Stressors in highly valued roles, religious coping, and mortality. Psychology and Aging, 13, 242–255. Kristal-Boneh, E., Harari, G., Melamed, S., & Froom, P. (2000). Association of physical activity at work with mortality in Israeli industrial employees: The CORDIS
study. Journal of Occupational and Environmental Medicine, 42, 127–135. Kune, G. A., Kune, S., & Watson, L. F. (1993). Perceived religiousness is protective for colorectal cancer: Data from the Melbourne colorectal cancer study. Journal of the Royal Society of Medicine, 86, 645–647. Loprinzi, C. L., Laurie, J. A., Wieand, H. S., Krook, J. E., Novotny, P. J., Kugler, J. W., Bartel, J., Law, M., Bateman, M., & Klatt, N. E. (1994). Prospective evaluation of prognostic variables from patient-completed questionnaires. North Central Cancer Treatment Group. Journal of Clinical Oncology, 12, 601–607. McCullough, M. E., Hoyt, W. T., Larson, D. B., Koenig, H. G., & Thoresen, C. (2000). Religious involvement and mortality: A meta-analytic review. Health Psychology, 19, 211–222. McMichael, A. J., & Hartshorne, J. M. (1982). Mortality risk in Australian men by occupational groups, 1968–1978: Variations associated with differences in drinking and smoking habits. Medical Journal of Australia, 1, 253–256. Melamed, S., Yekutieli, D., Froom, P., Kristal-Boneh, E., & Ribak, J. (1999). Adverse work and environmental conditions predict occupational injuries. The Israeli cardiovascular occupational risk factors determination in Israel (CORDIS) study. American Journal of Epidemiology, 150, 18–26. Naslund, G. K. (1997). Relationships between health behavior, knowledge, and beliefs among Swedish blue-collar workers. Scandinavian Journal of Work Environment and Health, 25, 100–110. Olsen, O. (1993). Impact of social network on cardiovascular mortality in middle aged Danish men. Journal of Epidemiology and Community Health, 47, 176–180. Oman, D., & Reed, D. (1998). Religion and mortality among the community-dwelling elderly. American Journal of Public Health, 88, 1469–1475. Siahpush, M., & Singh, G. K. (1999). Social integration and mortality in Australia. Australian and New Zealand Journal of Public Health, 23, 571–577. Strawbridge, W. J., Cohen, R. D., Shema, S. J., & Kaplan, G. A. (1997). Frequent attendance at religious services and mortality over 28 years. American Journal of Public Health, 87, 957–961. Waite, P. J., Hawks, S. R., & Gast, J. A. (1999). The correlation between spiritual well-being and health behaviors. American Journal of Health Promotion, 13, 159–162.
Social Science & Medicine 58 (2004) 595–602
Association of self-reported religiosity and mortality in industrial employees: the CORDIS study Allen Krauta, Samuel Melamedb,c,*, Daphna Goferb, Paul Froomb,c b
a Departments of Internal Medicine and Community Health Sciences, University of Manitoba, Winnipeg, Canada National Institute of Occupational & Environmental Health, Department of Occupational Health Psychology, P.O. Box 3, Raanana 43100, Israel c Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
Abstract This study examined the association between self-reported religiosity and mortality in industrial employees, while controlling for workplace and socioeconomic factors. Subjects were 3638 Jewish Israeli males who participated in a 12year follow-up study. During this period 253 deaths were recorded. The prevalence of negative workplace and sociodemographic factors: lower education, non-European origin, heavy physical work, blue-collar jobs and adverse job and environmental conditions, was highest among religious employees, and lower in traditional and nonreligious employees in descending order. Using Cox’s proportionate hazard model an age by religiosity interaction on mortality was uncovered. In younger employees (age o55 years) religiosity was associated with lower adjusted mortality, after controlling for negative workplace and sociodemographic factors. Compared with nonreligious employees, the hazard ratios for the religious and traditional employees were: 0.64 (p ¼ 0:016) and 0.39 (p ¼ 0:118), respectively. In older employees (age X55 years), religiosity was associated with higher adjusted mortality. The corresponding hazards ratios were 1.69 (p ¼ 0:011) and 1.08 (p ¼ 0:004), even after controlling for the above possible confounding variables. It was concluded that religiosity had a protective effect on mortality in younger employees, but the reverse was true for older employees. This opposite trend could not be explained by negative sociodemographic and workplace conditions. The possibility of involvement of yet another potent factor of social isolation was discussed. r 2003 Elsevier Ltd. All rights reserved. Keywords: Mortality; Religiosity; Blue collar; Employees; Industrial
Introduction The putative association between religion and health status has been studied for over a century (Galton, 1872). Religious attendance has been associated with a decrease in overall mortality (Oman & Reed, 1998; Koenig et al., 1999; Hummer, Rogers, Nam, & Ellison, 1999; McCullough, Hoyt, Larson, Koenig, & Thoresen, 2000; Strawbridge, Cohen, Shema, & Kaplan, 1997; *Corresponding author. National Institute of Occupational & Environmental Health, Department of Occupational Health Psychology, P.O. Box 3, Raanana 43100, Israel. Tel.: +972-9771-0094; fax: +972-9-771-2212. E-mail address: [email protected] (S. Melamed).
Goldbourt, Yaari, & Medalie, 1993). In a study of older California residents, Oman and Reed (1998) found that those who reported attending religious services had a lower mortality (age and sex adjusted relative hazard 0.64; 95% confidence intervals (CI) 0.52, 0.78) than those who did not. This relationship held true even after adjustment for health status, physical function, and social support. Similar results were reported in older community dwelling adults in North Carolina (Koenig et al., 1999) and in individuals residing in Alameda County, California (Strawbridge et al., 1997). Further support was provided by a study in civil servants (Goldbourt et al., 1993). Hummer et al. (1999) modeled the association of religious attendance with overall and cause-specific mortality using data from the National
0277-9536/03/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0277-9536(03)00282-X
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Health Interview Survey—Multiple Cause of Death linked file. They noted an inverse relationship after controlling for demographic, and certain health, socioeconomic, and social variables. Although the strength of the association varied by cause of death, its direction remained consistent across causes (Hummer et al., 1999). All of these authors recognized that the physical ability to attend religious services might have influenced their findings, but they did not believe it served as a confounding factor in the observed relationship. Studies that have used private measures of religious observance, such as praying at home or self-described religiosity, reported conflicting results with respect to mortality. Some found either no association with allcause mortality (Krause, 1998; Helm, Hays, Flint, Koenig, & Blazer, 2000) or decreased mortality only in subsets without impairments in activities of daily living (Helm et al., 2000). In Israel, a community study in Jerusalem yielded no association between religiosity and total mortality in men aged 60 years or older (Abramson, Gofin, & Peritz, 1982), whereas a kibbutz-based study found higher mortality on secular than on religious kibbutzim (rate ratio 1.93; 95% CI 1.44, 2.59) (Kark et al., 1996). In the latter work, there were no differences by sex, age, or cause of death, and the findings were consistent throughout the 16-year observation period. However, the authors failed to control for traditional risk factors. In studies of cancer patients, self-reported religiosity was identified as a protective factor for the development of colorectal cancer (Kune, Kune, & Watson, 1993), but it did not influence cancer mortality (Kune et al., 1993; Loprinzi et al., 1994). A more recent meta-analysis suggested that the association between religious involvement and mortality is modest (odds ratio 0.78; 95% CI 0.72–0.83) (McCullough et al., 2000). The positive effects of religion on health may be mediated through a number of tentative mechanisms. Individuals with strong religious faith report higher levels of life satisfaction, greater personal happiness, and fewer negative psychosocial consequences of traumatic life events (Ellison, 1991). Religious observance has also been associated with increased social support (Friedlander, Kark, Kaufmann, & Stein, 1985), more stable marriages (Kark et al., 1996; Strawbridge et al., 1997), and less involvement in risky behaviors (Waite, Hawks, & Gast, 1999; Hammermeister, Flint, Havens, & Peterson, 2001). Indeed, Kark et al. (1996) proposed that the contribution of religious observance to the creation of a less stressful environment could explain the mortality differences they found between the secular and religious kibbutzim. Differences in conventional risk factors have also been implicated: religious observance has been associated with lower smoking rates (Strawbridge et al., 1997; Friedlander et al., 1985), and a more protective plasma lipid and lipoprotein
profile (Friedlander et al., 1985; Friedlander, Kark, & Stein, 1987). It is noteworthy that the studies cited so far were performed in the community, and there is almost no research into the potential protective effect of religiosity on mortality in industrial employees. The majority of industrial employees (usually 60–70%) are blue-collar workers. It is well documented that blue-collar workers are exposed to a variety of concurrent adverse job and environmental conditions, such as safety hazards, physico-chemical agents, and psychosocial stressors (Anderson & Fletcher, 1979; Melamed, Yekutieli, Froom, Kristal-Boneh, & Ribak, 1999). They may also have poorer health habits and less access to good health care than white-collar workers (McMichael & Hartshorne, 1982; Naslund, 1997; Burton & Turrell, 2000; Korda, Strazdins, Broom, & Lim, 2002). While some studies found no difference in mortality rate by occupational status (e.g., Costa, Merletti, & Segnan, 1989), many others reported higher total and causespecific mortality (e.g., cancer, coronary heart disease, cerebrovascular disease) in blue-collar than in whitecollar workers (McMichael & Hartshorne, 1982; Aro & Hasan, 1987; Buring, Evans, Fiore, Rosner, & Hennekous, 1987). Thus, it is plausible that in industrial employees, the protective effect of religiosity may be masked by exposure to health-damaging factors in the work environment. The objective of this study was to determine whether self-reported religiosity is associated with overall mortality in Israeli industrial (mainly blue-collar) workers.
Subjects and methods Study population The original study population consisted of the 3816 Jewish men who participated in the Cardiovascular Occupational Risk Factors Determination in Israel Study (CORDIS) in 1985–1987 (Froom, Melamed, Kristal-Boneh, Gofer, & Ribak, 1996; Froom, Melamed, Kristal-Boneh, Benbassat, & Ribak, 1999; Melamed et al., 1999; Kristal-Boneh, Harari, Melamed, & Froom, 2000). The subjects were recruited from 21 industrial plants (metal work, textiles, light industry, electronics, food manufacturing and plywood production) throughout Israel for on-site screening of cardiovascular risk factors. They represented approximately 69% of the workforce at these sites. The study participants were found to be healthier, older, and less likely to be employed in large factories than the nonparticipants (Froom et al., 1999). At the time of the initial evaluation, information was collected on a variety of workplace and personal factors, and routine blood tests, an electrocardiogram, and a brief physical
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examination were performed. Testing was done at a rate of one or two plants per month until the entire sample was collected. One hundred and sixty-seven men were excluded from the analysis because of missing values. Data on mortality in the study group from 1987 to 1998 were obtained from the National Death Registry of the Israel Ministry of the Interior using the workers’ identity numbers that were obtained from the factory records and verified during the initial examination. Verification was obtained for all but 21 men (see Froom et al., 1999). Thus, this study was based on 3628 individuals and 42,322 person-years of follow-up. Results showed that 253 study participants died (7.0%) over the 12-year period. Level of religious observance At the interview, employees were asked their level of religiosity and were categorized into three groups on the basis of the findings: religious—individuals who strictly observed Jewish law; traditional—individuals who maintained the traditions of the faith but were more moderate and flexible in their observance than religious workers; and nonreligious. Self-reported religiosity has been used as part of or the entire defining variable (Friedlander et al., 1985; Friedlander, Kark, & Stein, 1986; Friedlander et al., 1987; Goldbourt et al., 1993) in other studies on religion and health in Israel, with a high concordance with questions measuring the degree of religious observance (Friedlander et al., 1987). The Spearman correlation coefficient between self-perception of religiosity and self-reported degree of observance of religious rules was 0.88. The correlation was 0.80 for an additional four-point religiosity scale based on the answers to questions about observance of specific rules and self-reported religiosity. Potential confounding variables Sociodemographic Potential sociodemographic confounders included age, educational level (more or less than 12 years), marital status, and ethnicity (country of origin of the father was used as a surrogate for ethnicity). Individuals were identified as North African, Asian or European if they could trace their ancestry to these areas. Those of African and Asian ancestry (Sephardic Jews) were grouped together, and those of European origin (Ashkenazi Jews) were analyzed separately. Occupational The industrial employees were broadly classified into white collar and blue collar. A blue-collar worker was defined as belonging to one of the following job categories: (a) direct production, (b) indirect production, (c) maintenance, (d) housekeeping, transportation,
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(e) first-line supervisor, foreman, (f) shift foreman, and (g) unclassified manual worker. All other employees were considered white collar. Managers and employees within each category were identified. As part of the CORDIS study, a comprehensive ergonomic evaluation was done of the work and environmental conditions at the workstations of each of the study participants (see Melamed et al., 1999). The 62-item Ergonomic Stress Inventory was used to collect data on 17 risk factors pertaining to safety hazards, overcrowding, cognitive and physical demands, and environmental stressors (for more details see Melamed et al., 1999). The internal consistency coefficient of the inventory was 0.95. Each participant was assigned a global ergonomic stress level (ESL) score, from 1 to 4, which was based on his average score across the 62 items of the inventory. The ESL was found to be a stable measure over a period of 2–4 years. In view of the threshold effect on association with injury risk (Melamed et al., 1999), scores 1 and 2 and scores 3 and 4 were combined to form two levels: low-ESL job and high-ESL job. Physical workload, which has been shown to predict mortality in this cohort (Kristal-Boneh et al., 2000), was abstracted from the workers’ subjective ratings. The ratings were made on a 4-point scale and then collapsed to two levels: no or light workload and moderate or high workload (Kristal-Boneh et al., 2000).
Statistical analysis The significance of differences between groups was tested as follows: t-test or one-way analysis of variance was applied for continuous variables, and w2 test for categorical variables. Cox’s proportional hazard regression model controlling for time was used to test whether the study groups differed in adjusted mortality rates when controlling for potential confounding variables. Two models were used: the first was adjusted only for age, and the second was adjusted for age and for the other sociodemographic and occupational factors evaluated in the study. In an additional step, we included the cross-products of religiosity and each of the control variables in the model in order to examine the effect of their interaction on mortality. Only age religiosity proved to have a significant effect. Therefore, the sample was further stratified by age (more or less than 55 years) in order to examine the association between religiosity and mortality within each stratum. All data were analyzed with SAS version 6.12. The reported measure of association was the hazard ratio (HR) with 95% confidence limits (95% CI), with the nonreligious employees serving as the comparison
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group. A p value of 0.05 was set as the level of significance.
Results The individuals excluded from the analysis because of missing data did not differ from the rest of the cohort by age, mortality, religiosity, national origin, smoking status, and performance of moderate or physical workload. Table 1 details the sociodemographic and occupational characteristics of the religious, traditional, and nonreligious groups. Compared to the nonreligious workers, the religious workers were older, more likely to be married, less likely to be of European origin, and less educated. A greater proportion were blue-collar workers. Their jobs were more physically strenuous jobs than those of the nonreligious workers and had a higher ESL, which signifies exposure to adverse work and environmental conditions. The differences for all these factors were statistically significant. Overall, the data showed a trend for several negative sociodemographic and occupational parameters associated with religiosity in descending order across the three study groups. Results of the proportionate hazard models are presented in Table 2. Analyses adjusted only for age (model 1) revealed higher all-cause mortality HRs in the religious and traditional groups than the nonreligious. When we adjusted for sociodemographic and workplace factors (model 2), the mortality HRs decreased and became nonsignificant. As noted in the Methods section, there was a significant interactive effect of age and religiosity on mortality (p for trend=0.02). Therefore, the study sample was stratified into younger (o55 years) and older employees. We then repeated the analysis presented in Table 1 for the younger and older groups separately to determine any possible differences in
sociodemographic and workplace characteristics between them. The results are presented in Table 3. Compared with the younger workers, the older group had a higher proportion of religious individuals and of individuals of non-European origin, and fewer years of education. They also had greater exposure to negative occupational factors, namely, high physical workload, blue-collar jobs, and high-ESL jobs. These findings indicate that there is an important difference between these two age groups that needs to be controlled for in further analyses. The results of the proportional hazard models applied to the younger and older employees are given in Table 4. The models were adjusted for the same variables as in the total-sample analysis. Different trends were found in the association between religiosity and mortality by age. In the younger group, adjusting only for age (model 1) yielded no significant association of religiosity with mortality. However, when we adjusted for all the sociodemographic and workplace variables (model 2), there was an association of religiosity with lower mortality, which reached a significant level in the religious group (HR=0.39, 95% CI 0.18–0.84) and trend level (but not statistically significant) in the traditional employees (HR=0.84, 95% CI 0.37–1.12). By contrast, in the older employees, religiosity was associated with increased adjusted mortality in both models. Thus, the trend in model 1 remained consistent even after controlling for all the potential confounders. The corresponding HRs in model 2 were 1.69 (95% CI 1.13–2.52) for the religious group and 1.99 (95% CI 1.23–3.10) for the traditional group.
Discussion The first major finding of this large cohort study of industrial employees was that for the total sample, the more religious group did not have a lower mortality rate
Table 1 Comparisons of sociodemographic and work factors among religious, traditional and non-religious members of the CORDIS data set (1985–1987)a Variable
Religious
Traditional
Non-religious
p value
Number Age, years Education o12 years Married European origin Blue-collar jobs Moderate or intense physical workload High-ESL jobs
694 47.2711.5 553 (79.7%) 649 (93.5%) 167 (24.1%) 627 (90.3%) 537 (77.4%) 484 (69.7%)
1512 44.4712.0 1044 (69.1%) 1358 (89.8%) 503 (33.3%) 1239 (81.9%) 1029 (68.1%) 999 (66.1%)
1422 44.4711.5 622 (43.7%) 1253 (88.1%) 1081 (76.0%) 894 (62.9%) 659 (46.3%) 718 (50.5%)
0.0001 0.001 0.001 0.001 0.001 0.001 0.001
ESL, ergonomic stress level. a Means and standard deviations are given for continuous variables; n and percentages are given for categorical variables.
ARTICLE IN PRESS A. Kraut et al. / Social Science & Medicine 58 (2004) 595–602 Table 2 Influence of self reported religiosity on all cause mortality: results of a proportional hazard regression (Cox) model Hazard ratio
95% CI
p value
Model 1 Age Non-religious Traditional Religious
1.10 1.00 1.40 1.55
1.09–1.12 — 1.04–1.87 1.11–2.15
0.0001 — 0.026 0.009
Model 2 Age Non-religious Traditional Religious Blue-collar jobs Physical workload High-ESL jobs Education o12 years Non-European origin Not married
1.11 1.00 1.20 1.21 0.92 1.48 1.04 1.35 1.13 1.25
1.10–1.12 — 0.82–1.77 0.87–1.65 0.60–1.40 1.05–2.07 0.77–1.41 0.96–1.89 0.84–1.52 0.76–2.05
0.0001 — 0.273 0.338 0.685 0.026 0.781 0.084 0.414 0.382
ESL, ergonomic stress level; CI, confidence interval.
Table 3 Comparison of some sociodemographic and workplace factors in younger (o55 years) and older employees (X55 years) in the CORDIS data set (1985–1987)a Variable
Age o55 years
Age X55 years
Number Age, years Non-religious Traditional Religious Education o12 years European origin Married Moderate or intense physical workload Blue-collar jobs High-ESL jobs Job tenure, years
2676 39.578.4 1082 (40.4%) 1131 (42.3%) 463 (17.3%) 1521 (56.8%)
952 60.174.3 340 (35.7%) 381 (40.2%) 231 (24.3%) 698 (73.3%)
0.001
1482 (55.4%) 905 (95%) 1592 (59.5%)
395 (41.5%) 2355 (88%) 633 (66.5%)
0.001 0.005 0.001
2006 (75.0%) 1587 (59.3%) 8.577.4
754 (79.2%) 614 (64.5%) 14.779.8
0.008 0.005 0.0001
p value
0.0001
ESL, ergonomic stress level. a Means and standard deviations are given for continuous variables; n and percentages are given for categorical variables.
than the nonreligious control group. This contradicts the findings of some community studies (Strawbridge et al., 1997; Oman & Reed, 1998; Koenig et al., 1999; Hummer et al., 1999; McCullough et al., 2000) and the study of white-collar employees (Goldbourt et al., 1993). Indeed, when we adjusted only for age, but not for
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workplace and sociodemographic factors, mortality was high in both the religious and the traditional employees. The corresponding HRs were 1.55 (95% CI, 1.11–2.15) and 1.40 (95% CI, 1.04–1.87) compared with the nonreligious employees. However, this difference was no longer significant (HR=1.21[0.87–1.65] and HR=1.20 [0.82–1.27], respectively) after adjusting for the other factors, namely, blue-collar work, heavy physical workload, adverse job and environmental conditions (high ESL job), lower education, and single status. A similar lack of association between religiosity and all-cause mortality was obtained in the community studies in which the various potential confounding variables were controlled for (Krause, 1998; Helm et al., 2000). An additional noteworthy finding pertaining to the total sample was the nearly linear association between religiosity and negative workplace and sociodemographic factors (see Table 1). A clear trend was noted when the religious and traditional groups were compared with the nonreligious employees. The former two groups were older, had a lower level of education, were less likely to be of European origin, performed more strenuous physical work, held more blue-collar jobs, and were exposed to worse job and environmental conditions (higher ESL). These parameters were most prevalent in the religious group. Thus, in this cohort of industrial employees, religiosity turned out to be a proxy of negative work and sociodemographic factors. Given the association between blue-collar work and increased mortality (see Introduction for review), it becomes clear why, in the present sample of industrial employees, religiosity was associated with increased mortality, and not the reverse. Further studies are needed to determine if these findings can be generalized to other populations of industrial employees. The second major finding of the present study was the interaction of the association between religiosity and mortality with age. Two opposite trends were uncovered by stratifying the total sample into younger (o55 years) and older (X55 years) employees. The protective effect of religiosity was observed only among the younger employees, and it became significant for the religious employees (HR=0.39, 0.18–0.84) only after adjusting for work and sociodemographic factors (see Table 4). The protective effect of religiosity was also observed among the traditional employees, but it did not reach statistical significance (HR=0.64, 0.37–1.12). These findings are important for two reasons: they show that the same protective effect of religiosity previously observed in community samples also holds true for younger industrial employees; and they show that the beneficial effect of religiosity is significant only for religious and not for traditional employees. By contrast, in the older employees, religiosity was associated with elevated mortality, even after adjusting
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Table 4 Influence of age stratification on the association of self-reported religiosity with all-cause mortality: results of a proportional hazard regression (Cox) model Age o55 years
Model 1 Age Non-religious Traditional Religious Model 2 Age Non-religious Traditional Religious Blue-collar job Physical work High ESL job Education o12 years Non-European origin Not married Number of deaths
Age X55 years
Hazard ratio
95% CI
p value
Hazard ratio
95% CI
p value
1.12 1.00 0.93 0.61
1.09–1.16 — 0.58–1.51 0.31–1.21
0.0001 — 0.1592 0.7775
1.07 1.00 1.77 2.17
1.04–1.11 — 1.21–2.58 1.44–3.25
0.0001 — 0.003 0.0002
1.12 1.00 0.64 0.39 0.90 1.11 1.17 1.85 1.47 1.15
1.08–1.15 — 0.37–1.12 0.18–0.84 0.43–1.87 0.61–2.01 0.66–2.08 1.01–3.39 0.85–2.52 0.46–2.91 78
0.0001 — 0.1188 0.0163 0.7752 0.7280 0.5820 0.0465 0.1650 0.7632
1.08 1.00 1.69 1.95 0.94 1.67 0.97 1.10 0.99 1.40
1.04–1.12 — 1.13–2.52 1.23–3.10 0.56–1.83 1.10–2.53 0.68–1.38 0.70–2.18 0.70–1.40 0.78–2.62 175
0.0001 — 0.011 0.004 0.819 0.017 0.855 0.652 0.935 0.265
for work and sociodemographic factors. This finding was significant in both the religious and the traditional groups (HR=1.69, 1.13–2.52 and HR=1.95, 1.23–3.10, respectively). In our initial analysis of the total sample, the excess mortality among the traditional and religious groups disappeared after adjusting for work and sociodemographic factors. On further analysis, this finding proved to be due to the inclusion of the younger employees in the total sample. For the younger employees, adjusting for these factors uncovered a protective effect of religiosity. The data here show that older employees, in general, have worse job status and worse work and environmental conditions than younger employees (Table 3). They also have significantly longer job tenure and lesser education. Thus, it seems that older employees have fewer options for mobility within the organization and less possibility to change undesirable job and environmental conditions. This may result in long exposure to negative agents that may have a cumulative and adverse effect on their health. Nevertheless, the elevated mortality in the older traditional and religious employees remained significant even after controlling for these potential confounding factors. This suggests that the elevated mortality was due to a factor or factors other than the job and environmental characteristics measured. One potentially powerful factor that was not systematically measured in the data-collection phase of the study, but which may partly account for the interaction of religiosity and age on total mortality, is lack of social
integration (social isolation and lack of social support) at work. There is sufficient evidence indicating that social isolation/lack of social integration is associated with increased total and cause-specific mortality (e.g., Olsen, 1993; Siahpush & Singh, 1999; Eng, Rimm, Fitzmaurice, & Kawachi, 2002). There is also more specific evidence showing that social ties and social support at work protect against total or cause-specific mortality (Johnson, Hall, & Theorell, 1989; Hibbard & Pope, 1992). In the study of Johnson et al. (1989) of the Swedish male working population, the groups showing the greatest risk of both morbidity and mortality were blue-collar employees working under highly isolated and strained conditions. In post-study interviews with the subjects in our cohort, we discovered that the religious and traditional employees tended to seek out peers at work with similar religiosity. If there were few such candidates in their immediate work environment, the older employees felt fairly isolated, whereas the younger ones were more likely to form social ties with their nonreligious co-workers instead. This difference may stem from the fact that 49% of the younger religious/ traditional employees were either born in Israel or immigrated before the age of 10 compared to only 4.7% of their older counterparts. Therefore, though both groups were exposed to adverse job and environmental conditions, the younger group may have had more access to the coping resource of social support. More systematic studies measuring social support at work are warranted to verify this casual observation. Other psychosocial factors need to be measured as well to
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explain our novel finding of an interaction between religiosity and age on total morbidity. An alternative explanation for the increased mortality among the older members of the cohort is the presence of a systematic selection bias. The CORDIS cohort was comprised of individuals who were healthier than the general population (standardized mortality ratio 71; 95% CI 60–83) owing to a combination of healthy worker and volunteer effects (Froom et al., 1999). It is possible, however, that these effects were selective, such that the older religious employees who were ill had no alternative but to remain in the workforce. A theoretical limitation of the study is our definition of religious involvement. The appropriateness of self-reported religiosity as a measure of religious involvement has been questioned by some authors (McCullough et al., 2000) as it may not truly measure religious commitment. Nonetheless, this is unlikely to have affected our study, because lines of religious involvement in Israel are not blurred. The vast majority of the self-reported religious Israeli Jews who took part in CORDIS were Orthodox. Furthermore, other studies conducted in Israel on the association of religion and health based their findings on self-reported religiosity (Goldbourt et al., 1993; Friedlander et al., 1985, 1986, 1987). Friedlander et al. (1987) reported a high concordance of self-reported religiosity with questions that measured the degree of religious observance. In our work, the validity of the religiosity measurement was reinforced by the finding that at least in the younger employees, the significant association between religiosity and mortality was in the direction observed in previous studies. Thus, we are confident that our definition of religiosity properly identified individuals with a religious commitment.
Conclusion This cohort study showed for the first time that the same protective effect of religion against mortality found in community samples and white-collar employees is also true for younger (o55 years) industrial employees. Both the younger and older (X55 years) religious/traditional employees in our study were predominantly blue-collar workers with lower education and higher exposure to adverse job and environmental conditions than their nonreligious counterparts. These sociodemographic and workplace factors were previously shown to be associated with elevated total and cause-specific mortality. Indeed, only after we controlled for them did we uncover the protective effect of religiosity in the younger employees. By contrast, in the older employees, religiosity was associated with elevated mortality in both the religious and traditional groups, even after controlling for the potent
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confounding variables listed above. This persistence of elevated mortality in the older group suggests that other, as yet unidentified factors, may be at play. However, our casual observation made after the completion of the study indicates that older religious employees are more socially isolated at work than younger ones and may therefore lack the important buffering resource of social support. Further studies of industrial employees are needed to replicate our findings and to determine the reason underlying the interaction of religious observance with age on total mortality.
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