March 5, 2009 -- It ain't over till it's over, Yogi Berra would say. Scientists might put it this way, though: In terms of your life span, it really does matter that you start exercising, quit the couch-potato habit, and give up smoking.
But even if you don't get started until middle age or later, you can prolong your life, a new study shows. Of course, it's better to quit bad habits and start good ones early, but middle age is not too late, say researchers at Uppsala University in Sweden.
They gathered data from 2,205 men aged 50 in 1970-1973, all completing surveys about leisure-time physical activity; the men were categorized as low-, medium- or high-activity types.
The men were examined again at age 60, 70, 77, and 82; changes in physical activity were recorded. Researchers also jotted down data on blood pressure, cholesterol levels, smoking status, alcohol use, and body mass index (BMI) at each survey.
The researchers also looked into the effect of changed physical activity between the times they were checked at age 50 and 60.
At age 50, nearly half of the men claimed a high level of physical activity, that is, at least three hours of recreational sports or heavy gardening per week. Thirty-six percent reported medium activity, amounting to walking and cycling; 15% were categorized as sedentary.
In the long run, the mortality rates were highest among the sedentary men, and lowest among the most active.
After 10 years, however, the mortality rate in the men who'd increased their activity had fallen to the same level as the ones who'd maintained high levels of physical fitness the whole time, the researchers say.
The benefit for the late starters was on par with quitting smoking.
However, during the first five years of follow-up, the mortality rate was higher in men who had increased their level of physical activity than in men with unchanged high physical activity, but the number of such deaths was small.
"Given the small numbers of deaths we are reluctant to place a strong emphasis on this increased risk, especially as mortality was not higher than mortality in men who continued to be sedentary," the researchers write.
The researchers say that after adjusting for other risk factors, men who reported high levels of physical activity from age 50 on were expected to live 2.3 years longer than the sedentary individuals, and 1.1 years longer than the men who'd originally reported medium physical activity.
Increased physical activity prolongs life in middle-aged men after "an induction period" of up to 10 years, the study says.
The study is published in BMJ online.