Even people who are older may see a longevity benefit from exercising: Older men who exercise 30 minutes a day tend to live longer than their couch-potato counterparts, a new study finds.

In the study of men in their 60s and 70s, those who routinely did 30 minutes of exercise six days a week had a 40 percent lower risk of dying over a 12-year period, compared with men who were sedentary.

"Even at the age of 73 years, physical activity is associated highly with [life span] between groups of sedentary and active persons," the researchers said in the study. [8 Tips for Healthy Aging]

In fact, exercise was so beneficial among the men in the study that its effects were on a par with those of quitting smoking, the researchers said. "Public health strategies in elderly men should include efforts to increase physical activity, in line with efforts to reduce smoking behavior," the researchers wrote in their findings, published online today (May 14) in the British Journal of Sports Medicine.

The new findings are based on the results from the Oslo Study, which investigated 15,000 men who were born in Norway between 1923 and 1932. The study began with a checkup in 1973 that included an assessment of the men's height, weight, cholesterol, blood pressure and smoking history, as well as how much they exercised on a weekly basis.

An analysis that began in 2000 looked at about 6,000 of the surviving men, and resulted in the new findings. Researchers repeated the checkup and questionnaire, and monitored the men for the next 12 years. Each participant was characterized as a sedentary person (who mainly watched TV or read), a light exerciser (who walked or cycled for at least four hours weekly), a moderate exerciser (who did formal exercise or heavy gardening or at least four hours weekly), or a vigorous exerciser (who did hard training or competitive sports multiple times weekly). 

During the 12-year monitoring period, a total of 2,154 out of the 5,738 men who had participated in both checkups died.

The researchers found that a small amount of exercise — less than an hour per week of light physical activity — was not associated with increased life span during the study. But compared with sedentary men, the men who exercised more than an hour per week had a 32-percent to a 56-percent lower risk of dying during the study, depending on other factors.

But the researchers also found that men who exercised vigorously, even for less than an hour weekly, were 23 percent to 37 percent less likely to die of cardiovascular disease or of any other medical cause during the study.

Vigorous exercise is key, the researchers said. The more time men spent exercising vigorously, the greater the reduction in their risk of dying. [7 Common Exercise Errors and How to Fix Them]

Men who made a habit of daily exercise at moderate to vigorous intensity lived, on average, five years longer than the men who were sedentary, even when the researchers controlled for the risk of diseases that increase with age, including heart disease and stroke, the researchers said.

In all, men who exercised 30 minutes daily for six days a week tended to live longer, irrespective of whether the exercise was light or vigorous, the researchers said.

Still, the researchers cautioned that this was an observational study, and it's unclear whether increased life span is linked to time spent exercising or rather to other factors. For instance, many of the participants who completed the second wave of the study were healthier than those who didn't, which may have lowered their risks of dying during the study.

But given that the longevity results are so striking when comparing men who exercised to those who didn't, it's likely that exercise does increase life span, the researchers said.

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