By Amy Norton
INDIANAPOLIS, Jun 05 (Reuters Health) - More often held up as a weapon
against heart disease, regular exercise may significantly reduce the risk of
developing cancer, Dallas researchers suggest.
In two large studies, researchers from the Cooper Institute found that men's
cardiovascular fitness--regardless of weight--was a key factor in whether they
died of cancer. Although body mass is believed to influence the risk of cancer
death, these findings suggest that fitness may be more important, according to
the investigators. Drs. Larry W. Gibbons and Carolyn E. Barlow reported the
findings here Friday at the annual meeting of the American College of Sports
Medicine.
In one study, Barlow's team followed more than 22,700 men aged 20 to 85 for
10 years. Men who were classified as "unfit" based on treadmill tests were 80%
more likely to die of cancer than fit men were. Those who were unfit and obese
were at greatest risk, being 2.6 times more likely to die of cancer than fit,
normal-weight men. However, the researchers found, if a man was fit, being
overweight did not raise his cancer risk.
"Fitness and fatness are different things," said study co-author Dr. Steven
N. Blair.
In the second study, Gibbons and colleagues looked specifically at lung
cancer. Previous research, he noted, has linked fitness to the risk of colon
cancer and breast cancer. With smoking a well-known primary cause of lung
cancer, only a couple of studies have delved into the possible role of aerobic
fitness in the disease, according to Gibbons. Yet his team found that among
nearly 26,000 men followed for an average of 10 years, the 20% who had the
lowest fitness levels were about 2.5 times more likely than the most-fit men to
die of lung cancer. The 40% of men classified as moderately fit were 1.5 times
more likely to die of the disease.
The link between fitness and lung cancer held when Gibbons and his
colleagues factored in risk factors such as smoking and age. In fact, they found
that among smokers and past smokers, those who were unfit or moderately fit were
more likely to die of lung cancer than fit men were. Gibbons told Reuters Health
that although his team did not examine the men's exercise habits, those who did
well on the treadmill tests were likely to be regularly active. He said the same
aerobic exercises that promote heart health may also help protect against
cancer.
The boost to the cardiovascular and immune systems that exercise provides
may explain the lower cancer risk, Gibbons said. Another possibility, he noted,
is that exercise shields healthy cells by ridding the body of cell-damaging free
radicals.
