Work activity and fatal heart attack studied by multiple logistic risk analysis.

A group of 3975 San Francisco longshoremen in cohorts classified annually by work activity (WA) was followed for fatal heart attack (FHA) over a 22-year period. In 57,632 person-years of follow-up, 410 men died from heart attack. A multi-factor logistic analysis was used to study work energy output adjusted for age, race, systolic blood pressure, smoking, body mass index, glucose intolerance and EKG status as predictors of FHA. After adjustment for these factors, men with a high WA of 7 kcal/min above basal metabolism at the beginning of a yearly follow-up period had a FHA rate about one-half the rate for men in the lowest WA category of 1 kcal/min above basal metabolism (p = 0.0003). In addition, the predictability of average WA during the four years preceding a yearly follow-up period was isolated to see if the lower risk associated with high WA derives from selective factors. After adjustment for factors described above and also for rate of change in WA used to represent selective factors, subjects with WA of 7 kcal/min still had about one-half the FHA rate observed for men at the lowest WA level (p = 0.0006). The findings from these and other phases of the analysis are consistent with the hypothesis that a substantial protective effect against FHA results from vigorous physical exertion.