Increasing Physical Activity in Middle Age Eventually Lowers Mortality Risk

30 mar 2009— Increased physical activity in middle age is eventually associated with reduced mortality risk to the same level as that in men with constantly high physical activity, according to the results of a population-based cohort study reported in the March 6 Online First issue of the BMJ.

"About half of all middle aged men in the West do not take part in regular physical activity," write Liisa Byberg, from Uppsala University in Uppsala, Sweden, and colleagues. "Whereas being physically inactive in younger years seems detrimental, we do not know whether an increase in exercise level later in life reduces mortality rates. If the impact on mortality could be compared with the effects of other changes in lifestyle habits it would be easier to communicate this potential health benefit."

The goal of this study was to assess how change in level of physical activity after middle age affects mortality rates and to compare that change vs the effect of smoking cessation. In Uppsala, Sweden, 2205 men aged 50 years from 1970 to 1973 were followed up for 35 years and were reevaluated at ages 60, 70, 77, and 82 years. The primary study endpoint was total (all-cause) mortality.

In the groups with low, medium, and high physical activity, the absolute mortality rate was 27.1, 23.6, and 18.4 per 1000 person-years, respectively, with a relative rate reduction attributable to high physical activity being 32% vs low physical activity and 22% vs medium physical activity.

During the first 5 years of follow-up, men who increased their physical activity level between the ages of 50 and 60 years continued to have higher mortality rates (adjusted hazard ratio [HR], 2.64; 95% confidence interval [CI], 1.32 - 5.27, vs unchanged high physical activity). However, after 10 years of follow-up, increased physical activity in these men was associated with decreased mortality rates to the level of men with unchanged high physical activity (HR, 1.10; 95% CI, 0.87 - 1.38).

This reduction in mortality rates associated with increased physical activity (HR vs unchanged low physical activity, 0.51; 95% CI, 0.26 - 0.97) was comparable vs quitting smoking (HR vs continued smoking, 0.64; 95% CI, 0.53 - 0.78).

"Increased physical activity in middle age is eventually followed by a reduction in mortality to the same level as seen among men with constantly high physical activity," the study authors write. "This reduction is comparable with that associated with smoking cessation."

Limitations of this study include sample restricted to men; crude assessment of physical activity by questionnaire, with risk for misclassification possibly leading to underestimation of the results; and possible bias related to the technique of last observed value carried forward.

"Efforts for promotion of physical activity, even among middle aged and older men, are important," the study authors conclude. "Increased physical activity in middle age increases longevity after an induction period of up to 10 years of no benefit."

The Swedish Research Council supported this study. The study authors have disclosed no relevant financial relationships.

BMJ. Published online March 6, 2009.