Sitting may boost cancer risk

Sitting for long periods of time may increase cancer risk, say researchers who recommend the avoidance of prolonged sedentary periods and stress the importance of regular exercise.

The research was presented this week at the American Institute for Cancer Research annual conference in Washington. 

Christine Friedenreich, an epidemiologist at Alberta Health Services, estimated that lack of physical activity is linked to nearly 100,000 cases of breast and colon cancer in the U.S. each year.

Based in part on those findings, the institute is urging people to make time for physical activity and break every hour of sitting with one to two minutes of activity.

Friedenreich's findings from the Alberta Physical Activity and Breast Cancer Prevention trial were also published in the October issue of the journal Cancer Prevention Research.

In the study, 320 women aged 50 to 74 were randomly assigned either to work up to exercising five days a week for at least 45 minutes or else to continue with their usual inactivity.

Friedenreich found differences in a marker of inflammation, known as C-reaction protein, over 12 months for exercisers compared with controls.

Inflammation markers

The study suggested that it isn't just lack of exercise that increases markers of inflammation, but that a sedentary lifestyle does, too.

Research is starting to point to how exercise may lower markers of inflammation, which in turn might lower cancer risk. But the possible links need to be investigated more thoroughly.

"Sitting time is emerging as a strong candidate for being a cancer risk factor in its own right. It seems highly likely that the longer you sit, the higher your risk," said Neville Owen, head of behavioural epidemiology at Australia's Baker IDI Heart and Diabetes Institute, who also presented findings at the conference.

"This phenomenon isn't dependent on body weight or how much exercise people do," Owen added in a release.

Owen's study measured waist circumference, insulin resistance and inflammation in adults who wore accelerometers to record their physical activity levels. Taking breaks as short as one minute was tied to lower levels of those biomarkers.

The institute offered these tips to help people fit in more activity:

• Set the timer on your computer to remind you every 60 minutes that it's time to step away from your desk and take a short walk down the hall.
• "Walk with me." Got a quick thing to discuss with a co-worker? Instead of sending an email, ask him or her to join you for a walk to hash it out on the go.
• Keep light hand weights in your office to use while reading email or talking on the phone.
• During phone calls and phone meetings, stand up and walk around.
• Your office or cubicle wall is all you need for simple activities like stretches, vertical push-ups and leg lifts.
• For a more vigorous activity break, ask your employer to put a punching bag or chin-up bar in your break room.