Objective: No previous long-term prospective studies have examined if workers with low cardiorespiratory fitness have an increased risk of cardiovascular mortality due to high physical work demands. We tested this hypothesis.
Method: We carried out a 30-year follow-up of the Copenhagen Male Study of 5249 employed men aged 40-59 years. We excluded from follow-up 274 men with a history of myocardial infarction, prevalent symptoms of angina pectoris, or intermittent claudication. We estimated physical fitness [maximal oxygen consumption (VO (2)Max)] using the Astrand cycling test and determined physical work demands with two self-reported questions.
Results: In the Copenhagen Male Study, 587 men (11.9%) died due to ischaemic heart disease (IHD). Using men with low physical work demands as the reference group, Cox analyses--adjusted for age, blood pressure, smoking, alcohol consumption, body mass index, diabetes, and hypertension--showed that high physical work demands were associated with an increased risk of IHD mortality in the least fit [VO (2)Max range 15-26, N=892, hazard ratio (HR) 2.04, 95% confidence interval (95% CI) 1.20-3.49] and moderately fit (VO (2)Max range 27-38, N=3037, HR 1.75, 95% CI 1.24-2.46), but not among the most fit men (VO (2)Max range 39-78, N=1014, HR 1.08, 95% CI 0.52-2.17). We found a similar, although slightly weaker, relationship with respect to all-cause mortality.
Conclusions: The hypothesis was supported. Men with low and medium physical fitness have an increased risk of cardiovascular and all-cause mortality if exposed to high physical work demands. Ours observations suggest that, among men with high physical work demands, being physically fit protects against adverse cardiovascular effects.