Background: Physical activity (PA) is inversely associated with mortality in the general population. We wanted to quantify the association of self-reported PA with mortality from all causes, ischaemic heart disease (IHD) and stroke, and compare it with other known risk factors in different age segments.
Methods: The Bergen Clinical Blood Pressure Survey examined a sample of 6811 Norwegian men and women in 1965-71 with follow-up until 2005-07. Cox proportional hazard regression ratio (HR) and population attributable fraction (PAF) were calculated for the old (>65), middle-aged (45-64) and young adults (22-44), respectively. We minimized confounding and bias by progressive comprehensive adjustments and subgroup-analyses (excluding early follow-up deaths, participants with self-reported disease and participants with changes in their PA-level prior baseline due to disease).
Results: The HR [95% confidence interval (CI)] associated with a high PA-level was 0.63(0.56-0.71), 0.66(0.52-0.83) and 0.66(0.47-0.93) for mortality from all causes, IHD and stroke, respectively (reference: no participation in any of the listed activities, adjusted for age and gender). PAF (95% CI) of no/low activity (reference: any activity) was consistent across all age groups, varying from 7.3% (3.4-11.4) in the young adults to 9.1% (3.6-15.3) in the old. PAF of smoking and high s-cholesterol declined with increasing age [smoking from 19.9% (15.3-24.7) to 1.5% (-1.3 to 6.2) and s-cholesterol from 11.5% (5.6-17.5) to -9.5% (-18.1 to -0.7)], whereas PAF of hypertension increased from 5.3% (2.1-9.1) to 18.9% (8.3-28.4).
Conclusion: The relative importance of traditional risk factors varies between the age groups, but physical activity is a major health promoting factor across all age segments and should be encouraged particularly in an ageing population.