In a new study from Norway, researchers have discovered that even a little exercise late in life may help men live longer.

"Even in the elderly, there is a lot to gain by being moderately active as compared to being sedentary," said study lead author Ingar Holme, professor emeritus at the Norwegian School of Sport Sciences in Oslo. In the new study of older men, researchers found that increasing physical activity had benefits to life span much like quitting smoking.

"Given the evidence, physical activity is probably an important factor in getting people to age successfully," Holme says. "But there are many things that we don't know in this field."

For the study, researchers monitored 6,000 Norwegian men born from 1923 to 1932 who underwent a health check in 1972-1973 and then again in 2000.  Monitoring of the men then continued for almost 12 years.

Of the men who were classified as sedentary, they spent a lot time reading and/or watching TV.  Men who were moderately active usually exercised, played sports or did heavy gardening for at least four hours each week while men who were classified as vigorously active engaged in hard training or competitive sports several times a week.

During the study, more than 2,000 men died.  Holme said 51 percent of men who were sedentary in their 70's died from any cause, compared to about one-quarter of those who were moderately to vigorously active.

Researchers found that just 30 minutes of moderate activity six days a week was associated with a 40 percent lower risk of death.  More exercise even reaped great benefits, decreasing the odds of death from both heart disease or any cause.

Looking further back, men who were in their 40s and lived a sedentary life lived five fewer years on average than those who were the most active.

The study, however, didn't take into account the risk of injury from exercise, and it didn't look at which came first, poor health or lack of exercise.  It also didn't proved that regular exercise caused men to live long, only finding that there was an association between the two.

However, researchers believe the study fits with previous research that links physical activity to better health and quality of life.

"While we may not fully understand all the mechanisms, we do know that exercise, especially as we age, is a critical component in preventing [mental] decline, lowering the risk for depression and other mental health challenges, maintaining muscle mass and function, enhancing cardiorespiratory fitness, increasing social interactions, maintaining balance and coordination, and reducing fall risk," said Brad Roy, executive director of the medical fitness center at Kalispell Regional Medical Center in Montana.

The study says nothing about women, but other research suggests they gain similar benefits, said Roy, who wasn't involved with the study.