THURSDAY, March 5 (HealthDay News) -- Men who start exercising when they are 50 can extend their life span by more than two years, Swedish researchers say.

Their study found that exercising has the same beneficial effect on length of life as quitting smoking in middle age.

Nonetheless, almost half of middle-age men don't exercise, the researchers said. But Dr. Karl Michaëlsson, a senior lecturer in the Department of Surgical Sciences at Uppsala University and the study's lead author, said the study offers more proof that "it's not too late for a man after the age of 50 years to invest in health and longevity by becoming more physically active."

"Men who reported an increase in physical activity to a high level at age 60 years had, after an induction period of approximately 10 years, the same mortality risk as those who continued to have a high physical activity from age 50 to age 60 years," he said. "The magnitude of the reduction in mortality risk with increased physical activity corresponded to that of smoking cessation."

The report was published in the March 6 online edition of BMJ.

For the study, Michaëlsson's team collected data on 2,205 men who were 50 years old and then surveyed them again when they were 60, 70, 77 and 82. Each time, they were questioned about their level of physical activity as well as their weight, blood pressure, cholesterol levels, smoking habits and alcohol use.

After adjusting the data for other lifestyle factors, the researchers found that men who led sedentary lives were most likely to die during the follow-up period, and those who had the highest level of physical activity were least likely to die during that time.

In fact, men who exercised the most when they were 50 lived, on average, 2.3 years longer, and men who did moderate exercise lived 1.1 years longer than men who reported the lowest levels of exercise. It might take five to 10 years to see, but men who exercise in middle-age live longer, the researchers noted.

And compared with smoking cessation, "the reductions in mortality risk were found to be equal," Michaëlsson said. "Everyone knows that smoking is hazardous for health and increases mortality risk, but it is not generally known that low physical activity has a similar impact on mortality risk as smoking."