A pair of studies presented at a conference last week have found that women are less likely to die from lung cancer if they engage in regular and vigorous physical exercise, and that the risk of developing breast cancer can be cut by a third if a woman remains habitually active.
One study, conducted by researchers at Stanford University in the US, found that even women who smoked had a lower risk of developing lung cancer if they exercised when compared to their couch potato smoker peers. "We saw that as levels of physical activity increase, risk of lung cancer decreased," lead researcher Ange Wang, said in a press release. The other study, by a team from the International Prevention Research Institute in France, linked physical exercise to lower instances of breast cancer, so long as they'd not been taking hormone replacement therapy.
Presented at the 2015 meeting of the American Society of Clinical Oncology in Chicago last week, the studies are an exercise in correlation does not equal causation but the results should come as no surprise, given the known and overwhelming benefits of frequent physical activity.
The Stanford study looked at data from the Women's Health Initiative, which was a federally funded project that monitored nearly 162,000 women aged between 50 to 79 years across 40 hospitals in the US. Over 12 years, just over 2,200 women were diagnosed with lung cancer and 1,400 of them died from the disease, but the more exercise they did - measured by minutes per week - the less likely they were to be one of these unlucky few. "It seems to indicate that you don't have to kill yourself. It doesn't need to be strenuous. You just have to put the time in," says Wang.
The link even extended to women who were current or former heavy smokers: while their risk of developing lung cancer was obviously still higher than those who didn't smoke, their risk was lower if they exercised than smokers who didn't.
Wang and her team are yet to show a cause-and-effect link between the two factors.
The French study, which focussed on the risk of breast cancer in women, reviewed 38 studies published between 1987 and 2014, involving 4.18 million women and more than 116,000 cases of breast cancer. Those who engaged in the highest levels of physical activity each week saw up to a 20 percent lower risk in developing breast cancer, when compared to those who did not exercise. And the results showed that it was never too late to start - if a woman started exercising vigorously from four to seven hours a week, their risk seemed to decrease by 31 percent.
"This reduction occurred irrespective of the type of physical activity, the place of residence, obesity and menopausal status," one of the team, biostatistician Cecile Pizot, said in the press release. "Also, breast cancer risk seems to decline with increasing physical activity, and we observed no threshold."
It's now up to both teams to figure out exactly why the link between exercise and decreased link in lung and breast cancer exists, and why it appeared to be negated in those who were taking hormone therapy. "I'm sure it involves multiple factors," one of the team, oncologist Gregory Masters, said, adding that by simply lowering your body weight and therefore levels of inflammation, you could be actively lowering your risk of developing cancer. And more strenuous activity in your lungs might be limiting the capacity for cancerous agents from cigarettes to accumulate.