Moderate daily exercise
can help fend off the common cold, new research
suggests.
Older women who walked
for a half-hour daily for a year reported
half the number of colds as women of similar
age who didn't exercise, U.S. researchers
report in the November issue of the American
Journal of Medicine.
"There's been a lot of anecdotal evidence
that exercise prevents infection, and colds
in particular," said the study's lead
author, Cornelia M. Ulrich, an associate member
of the Fred Hutchinson Cancer Research Center
in Seattle.
Her team's study is the first randomized
clinical trial to look at the impact of moderate
physical activity on the actual number of
colds contracted, she said.
Ulich's team evaluated 115 overweight Seattle-area
women who had previously shunned regular exercise.
All were past menopause, and averaged 61 years
of age.
Fifty-three of the women were assigned to
the exercise group, where they spent 30 minutes
daily, five days a week, doing moderate-intensity
activity like brisk walking. Another 62 were
assigned to a control group, which only attended
a weekly 45-minute stretching class.
All the participants were asked not to change
their dietary habits. And they answered questionaires
every three months on cold symptoms or other
upper respiratory infections.
"Overall, the non-exercisers got two
times the number of colds," Ulrich said.
The benefit of exercise in reducing colds
was even greater in the final three months
of the study, she added.
"In the final three months, one of 10
exercisers had a cold, but one of three of
the non-exercisers did," Ulrich noted.
"Couch potato" types, "were
more than three times as likely to get a cold,"
she said.
Ulrich also said that there was no overall
difference in the risk of upper respiratory
infections (like flu) between groups, but
added that this could be due to the fact that
more non-exercisers had received the flu vaccine.
While 42 percent of the stretchers had gotten
the flu vaccine during the study, only 23
percent of the exerciser had.
Experts aren't sure just how exercise works
to battle colds. "We think there are
[positive] changes in the immune system,"
Ulrich said.
The study results make sense to David Nieman,
a professor of health and exercise science
at Appalachian State University, Boone, N.C.,
and a veteran researcher of the exercise/colds
link. In his own research, Nieman found that
walkers experienced half the number of days
of cold symptoms as non-exercisers.
The new study, he said, adds more valuable
information to the mix.
"I think it is another set of data that
now adds to the growing awareness that one
of the most powerful ways of keeping your
sick days down is to do nearly daily [physical]
activity," Nieman said.
In a report on exercise immunology, published
in 2003 in Current Sports Medicine Reports,
Nieman noted that positive immune changes
take place during each bout of moderate physical
activity. Over time, this translates to fewer
sick days from colds or flu, he said.
But the new study does have some potential
weaknesses, added Dr. Paul D. Thompson, director
of cardiology at Hartford Hospital who co-authored
an editorial that accompanied the journal
report.
Infections were self-reported, he noted.
"Colds were reduced [in the exercisers],
but there was not a reduction in upper respiratory
infections [overall]," he said. "Could
subjects have 'reclassified?'" In other
words, they may have described a cold as the
flu, he said.
He also noted that the "control"
stretching group worked in close proximity
during the 45-minute sessions, which could
have have left them more vulnerable to catching
and spreading infection than the more-solitary
walkers.
Even so, he said, the new study suggests
there's yet another good reason to exercise.
Accoring to Thompson, regular physical activity
"probably reduces the chance of colds,
probably reduces the incidence of heart attacks
and heart disease, helps prevent diabetes,
helps control body weight and keeps you out
of the nursing home."
