Jack and Elizabeth Menager walk near their home in Los Angeles in 2007. A new study suggests it's never too late for men to get the life-extending benefits of exercise. (Reed Saxon/Associated Press)

Men who start exercising regularly in their 50s may extend their lifespans by more than two years — about as much time as men who stop smoking, a new study suggests.

Swedish researchers followed more than 2,200 men for more than 20 years for the study, which appears in Friday's online issue of the British Medical Journal.

Men who increased their activity levels after turning 50 ended up living as long as those who were exercising regularly before then, the researchers found.

"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," Dr.Karl Michaëlsson, a senior lecturer in the department of surgical sciences at Uppsala University and his colleagues concluded.

"This reduction is comparable with that associated with smoking cessation."

The researchers looked at men when they were 50 and then again when the subjects were 60, 70, 77 and 82.

During each survey, the subjects were asked about their physical activity levels, weight, blood pressure, cholesterol levels, smoking habits and alcohol consumption.

High levels of physical activity amounted to at least three hours of sports or heavy gardening each week. A moderate level was the equivalent of several hours of walking or cycling. People who spent most of their free time watching TV were considered sedentary.

By the end of the study, 60 per cent of the men had died.

Other factors affect longevity

The team found that those who were the most physically active at 50 lived 2.3 years longer than sedentary men and 1.1 years longer than those who reported medium levels of activity, after taking into account weight, alcohol intake and smoking.

"An increase in physical activity has the same impact on lowering mortality rate in the long term as smoking cessation," the study's authors wrote. "Thus, efforts for promotion of physical activity, even among middle-aged and older men, are important."

It's unclear whether the findings would apply to women.

Getting little or no exercise increases the risk for heart disease and several types of cancer, according to the U.S. National Cancer Institute.