To examine whether elevated resting heart rate (RHR) is an independent risk factor for mortality or a mere marker of physical fitness (VO2Max).
This was a prospective cohort study: the Copenhagen Male Study, a longitudinal study of healthy middle-aged employed men. Subjects with sinus rhythm and without known cardiovascular disease or diabetes were included. RHR was assessed from a resting ECG at study visit in 1985-1986. VO2Max was determined by the Ã?strand bicycle ergometer test in 1970-1971. Subjects were classified into categories according to level of RHR. Associations with mortality were studied in multivariate Cox models adjusted for physical fitness, leisure-time physical activity and conventional cardiovascular risk factors.
2798 subjects were followed for 16 years. 1082 deaths occurred. RHR was inversely related to physical fitness (p 90 had an HR (95% CI) of 3.06 (1.97 to 4.75). With RHR as a continuous variable, risk of mortality increased with 16% (10-22) per 10 beats per minute (bpm). There was a borderline interaction with smoking (p = 0.07); risk per 10 bpm increase in RHR was 20% (12-27) in smokers, and 14% (4-24) in non-smokers.
Elevated RHR is a risk factor for mortality independent of physical fitness, leisure-time physical activity and other major cardiovascular risk factors.
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No previous long-term studies have examined if workers with low physical fitness have an increased risk of cardiovascular mortality due to long work hours. The aim of this study was to test this hypothesis.
The study comprised 30-year follow-up of a cohort of 5249 gainfully employed men aged 40-59years in the Copenhagen Male Study. 274 men with cardiovascular disease were excluded from the follow-up. Physical fitness (maximal oxygen consumption, Vo(2)max) was estimated using the Åstrand bicycle ergometer test, and number of work hours was obtained from questionnaire items; 4943 men were eligible for the incidence study.
587 men (11.9%) died because of ischaemic heart disease (IHD). Cox analyses adjusted for age, blood pressure, smoking, alcohol, body mass index, diabetes, hypertension, physical work demands, and social class, showed that working more than 45h/week was associated with an increased risk of IHD mortality in the least fit (Vo(2)max range 15-26; HR 2.28, 95% CI 1.10 to 4.73), but not intermediate (Vo(2)max range 27-38; HR 0.94, 95% CI 0.59 to 1.51) and most fit men (Vo(2)max range 39-78; HR 0.91, 95% CI 0.41 to 2.02) referencing men working less than 40h/week.
The findings indicate that men with low physical fitness are at increased risk for IHD mortality from working long hours. Men working long hours should be physically fit.
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.
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.
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.
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.
Comment In: Scand J Work Environ Health. 2010 Sep;36(5):349-5520686737
Investigate whether high physical work demands increase risk of ischemic heart disease (IHD) mortality among men of low social class with low physical fitness.
Thirty-year follow-up in the Copenhagen Male Study of 5249 men aged 40 to 59 years without cardiovascular disease. Physical fitness was estimated using the Åstrand cycling test, and physical work demands determined by two self-reported questions.
Among 2707 low social class men, multiple-adjusted Cox proportional hazard ratios showed an almost threefold increased risk of IHD mortality among men with high physical work demands and low physical fitness, but not among men with a high physical fitness, referencing men with low physical work demands.
These findings among low social class men support that high physical work demands increases the risk of IHD mortality among those with low physical fitness.