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 (VO₂Max)] using the Åstrand 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 [VO₂Max range 15–26, N=892, hazard ratio (HR) 2.04, 95% confidence interval (95% CI) 1.20–3.49] and moderately fit (VO₂Max range 27–38, N=3037, HR 1.75, 95% CI 1.24–2.46), but not among the most fit men (VO₂Max 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.

Key terms all-cause mortality; cardiovascular health; Copenhagen Male Study; fitness; health; ischaemic heart disease; mortality; occupational health; occupational physical activity; physical activity; physical demands; physical fitness; work