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14.05.2012

Just 15 minutes' walking per day extends life expectancy

People who can't stand physical exercise could at least try to walk or cycle for a quarter of an hour a day. This minimal amount of exercise is enough to noticeably lower their mortality risk, according to researchers at the Taiwanese Institute of Population Science.

Exercise, willpower & health
Scientists are always telling us that we should get 30 minutes of exercise every day, but the amount of people who actually have the willpower to do so are few and far between. It seems that half an hour of exercise a day is too much to expect from most mortals. So the researchers posed the question as to whether less exercise can also have a protective effect on health.

Study
The researchers tried to answer this question in a study that involved monitoring four hundred thousand Taiwanese for eight years. The researchers divided the participants into five groups according to their exercise regimes.

Movement was converted to the equivalent of walking at a reasonable speed. This meant that the inactive-group walked for less than 15 minutes each day. The low-group walked for about 15 minutes each day, the medium-group for 30 minutes, the high-group for 60 minutes and the very-high-group for two or more hours.

Results
Over the eight-year period, the mortality risk was lower, the more exercise the Taiwanese got. Among those who walked for 15 minutes a day the mortality risk was 15 percent less than among those in the inactive group.

Exercise reduced above all the likelihood of dying from diabetes or cardiovascular disease. For these two causes of death, the people in the very high group were half as likely to die from them compared with those in the inactive group. When it came to cancer, the mortality risk was a quarter less in the very high group than in the inactive group.

The miniscule amount of exercise of 15 minutes a day lowered the mortality risks in all population groups the researchers could think of: young people, old people, smokers, drinkers, those with high blood pressure, diabetics...

Conclusion
For the Taiwanese that get 15 minutes a day of exercise, then each extra 15 minutes of exercise reduces their mortality risk by four percent, and their likelihood of dying from cancer by one percent. "Our results suggest that one in nine deaths from cancer in individuals in the inactive group could have been averted if they did 15 min of moderate-intensity daily exercise", the researchers write.

The maximum effect of moderate-intensive exercise is reached at 2 hours per day. Exercising for longer, as far as the researchers could tell from the data they collected, does not offer more protection.

Vigorous physical activity, such as running, is more effective than moderately vigorous activity. The protective effect of vigorous activity reaches its maximum at one hour a day.

"The minimum amount of exercise reported in this study is half of that recommended worldwide, but individuals are more likely to do 15 min of daily exercise than 30 min of daily exercise", the researchers conclude. "Furthermore, once an individual does 15 min of daily exercise regularly, they might be more likely to increase the amount of time they spend exercising per day. With this potential increase in exercise in mind, a recommendation of 15 min of daily exercise should be promoted to east Asian populations."

Source:
Lancet. 2011 Oct 1;378(9798):1244-53.

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