Cancer Research News
Exercise Can Reduce a Smoker's Lung Cancer Risk, but Quitting Smoking Is Still Most Important
PHILADELPHIA (December 11, 2006) − In a study of more than 36,000
women, researchers observed that smokers can reduce their risk of
developing lung cancer by being physically active. However, they
strongly caution that any relative benefit is dwarfed by the benefits
gained from quitting smoking.
The researchers, from the Universities of Minnesota and Pennsylvania,
report in the December issue of Cancer Epidemiology Biomarkers &
Prevention that a high level of physical activity in women who smoked
reduced their relative risk of developing lung cancer by 72 percent.
Moderate activity among smokers was associated with a 65 percent risk
reduction, and lower relative risks were also seen in former smokers who
had moderate or high activity levels.
While this may sound like welcome news to female smokers who don’t want
to quit, the investigators emphasize that the absolute risk of
developing lung cancer is still much greater in current and former
smokers regardless of activity level.
“The most important thing a smoker can do to reduce risk is to quit
smoking. That said, exercising and being active can offer a marginal
change in risk,” said the study’s lead author, Kathryn Schmitz, Ph.D. an
assistant professor at the University of Pennsylvania. Schmitz worked on
the study with a team of researchers while on faculty at the University
In other words, she says, a physically active smoker has a 35 percent
lower risk of lung cancer than a sedentary smoker, but if both smokers
quit, they would both reduce their risk by as much as 10- or 11-fold.
“Smokers who exercise are at a 35 percent lower risk of developing lung
cancer relative to smokers who don’t exercise, but if you smoke at all,
your risk of developing lung cancer is 10- to 11- fold higher than if
you didn’t smoke.”
“The helpful message from this study is that if a smoker is having
trouble quitting, exercise can be a first step toward better health,”
The findings were derived from the Iowa Women’s Health Study, which in
1986 began to follow almost 42,000 women between the ages of 55 and 69.
Over the years, five questionnaires were sent to the participants who
recorded their smoking status and physical activity among other
variables. This analysis, which began in 2002, included 36,410
participants, including 777 women diagnosed with the cancer. Among this
group, 125 were non-smokers, 177 were former smokers, and 475 were
Compared to women who were physically active, women with a low physical
activity level at the baseline analysis were more likely to smoke, less
likely to have a high school education and more likely to be obese.
Among smokers, the most number of cancer cases (324) were seen among
women who currently smoked and had low activity, and the lowest number
(40) was in the group of women who formerly smoked and were highly
active. Compared to never smokers, current and former smokers had
proportionally more squamous cell and small-cell lung cancer, which can
be harder to treat than other subtypes.
Researchers don’t know why activity could lower lung cancer risk, but
suggest that improved pulmonary function may reduce both the
concentration of carcinogenic particles in the smoker’s airway and the
extent to which they are deposited in the lungs. They also theorize that
exercise training improves immune function and reduces the inflammatory
responses that can impact cancer development.
“This may be useful information for smokers who are not currently
willing to attempt smoking cessation or have recently failed a quit
attempt,” says Schmitz. “But even if there was a significant risk
reduction, quitting smoking is unarguably the most important action a
person can take for reduction of lung cancer risk.”
The study was funded by the National Cancer Institute.
Source: American Association for Cancer Research
Cut Back on Cigarettes May Negate Benefit through Compensatory Smoking
Successful Lung Cancer Surgery Not Enough to Break Nicotine Dependence
in Many Smokers (Dec 2006)