About 90% of the original 5,115 subjects participated in the 1987/1988 examination; of these, 4,211 had job content scores. About 77% participated in the 1995/1996 examination; 3,865 had job content scores. About 74% participated in the 2000/2001 examination, with 3,042 having CAC measures. About 72% participated in the 2005-2006 examination, with 3,137 having CAC measures. Of 3,695 participants who had CAC assessed at either the CARDIA year 15 or year 20 exam, 88% had job strain scores from year 2 (1987/1988), and 89% had job strain scores from year 10 (1995/1996) (). Conversely, 77% of those with job strain scores at year 2 and 85% of those with job strain scores at year 10 had CAC measured at either year 15 or year 20.
Sample Sizes for CARDIA Participants (n=5115 at baseline in 1985/1986) With Job Content and Coronary Artery Calcium Measures.
About equal percentages of those with and without CAC measures reported being in any combination of low/high demand and low/high latitude jobs at either earlier exam. For example, the percentages with low latitude/low demands, high latitude/low demands, low latitude/high demands, and high latitude/high demands at the year 10 exam with versus without a scan were 31% vs 33%, 24% vs 23%, 21% vs 19% and 24% vs 24% respectively. Likewise, the percentage of participants with a CAC score differed little by whether their job characteristics were measured at year 2 or year 10.
About 23% of participants in the year 2 exam and 21% of those at the year 10 exam had high-strain jobs (). Black men (P=0.02) and black women (P=0.03) were somewhat more likely to report having high-strain jobs than white men and women, respectively. White women had the highest percentage of jobs with high decision latitude and high psychological demands. As would be expected, participants with managerial occupations and those with higher education were more likely to report high job decision latitude at both year 2 and year 10 than were laborers and those with less than a high school education, respectively (P=0.0001 for occupation overall and education overall for both exams) (). High psychological job demands were reported most frequently by respondents in managerial occupations (P= 0.002 at year 2 and P= 0.0001 at year 10 for overall association between high psychological demands and occupational group) (). Job strain was greatest among the operators/ fabricators/ laborers occupational group (P =0.0001 for overall association for exams) ().
Distribution of Selected Characteristics of CARDIA Study Participants, by Age and Sex, 1987/1988 and 1995/1996
Percentage of CARDIA Participants With Jobs Having (A) High Decision Latitude, (B) High Psychological Demands, and (C) High Strain (Low Decision Latitude, High Demands), by Education Level and Occupation.
About 17.7% of the participants had a positive CAC for the combined year 15 (prevalence=9.6%) and year 20 (prevalence=18.5%) examinations. Previous CARDIA analyses observed that male sex and older age were positively associated with CAC (25
). In unadjusted analyses, job characteristics based on high/low psychological demands and decision latitude at either year 2 or year 10 was not associated with the presence of CAC (). Among women at the year 2 exam, there was an apparent race difference in the direction of association of decision latitude with prevalence of CAC, with white women having a higher prevalence of CAC with higher decision latitude and black women having a lower prevalence with higher latitude, although differences within race-sex groups were not significant. Among the total sample, participants in blue collar jobs (precision/craft/repair and operators/fabricators/laborers) at year 2 and year 10 tended to show a higher prevalence of a positive CAC than workers in other occupational categories (P
=0.0001 for overall association).
Unadjusted Prevalence of Coronary Artery Calcium by Job Characteristics, Occupational Category, Race, and Sex: the CARDIA Study, 1987—2006
When examined as either continuous or as categorical variables in multivariate models, decision latitude, psychological demands, and job strain were not associated with the probability of a positive CAC (). However, occupational category was related to a positive CAC. Those in managerial/professional or technical/sales/support occupational categories at either year 2 or year 10 had a lower likelihood of a positive CAC than were those in the operators/fabricators/laborers category. After adjusting for systolic and diastolic blood pressure, body mass index, physical activity, cholesterol, smoking status, and alcohol use status, associations between occupational category and probability of subsequent CAC risk remained significant for year 10 occupation but were attenuated for year 2 occupation (data not shown).
Adjusted Odds Ratios for Coronary Artery Calcium in 2000/2001 or 2005/2006 by Job Characteristics and Occupational Category in 1987/1988 and 1995/1996: the CARDIA Study, 1987–2006
Among 2943 participants with a CAC measurement and with job characteristics measured at both years 2 and 10, there were no substantial differences in the prevalence of CAC based on changes in decision latitude, psychological demands or job strain. For example, the unadjusted prevalence of CAC was 13.0% among those with job strain at both years 2 and 10 and 18.2% among those with no job strain at both years; differences were not statistically significant in multivariable adjusted models ().
Association Between Changes in Job Characteristic and Job Strain Status from year 2 (1987/1988) to year 10 (1995/1996) and the Probability of CAC at Year 15 (2000/2001) or year 20 (2005/2006): the CARDIA study, 1987–2006
We tested the interaction of race and decision latitude with the probability of CAC among women at year 2 suggested in the crude analyses (). With analyses restricted to women, we entered an interaction term of race X decision latitude (as a continuous variable) into the models along with the lower-order terms and other covariates. The interaction term was of borderline significance (P=0.053), with an increase in decision latitude among black women being associated with a lower likelihood of CAC compared to white women.