Terry Boyle, PhD candidate/research officer, Epidemiology Group, Western Australian Institute for Medical Research/School of Population Health, University of Western Australia, Nedlands, Western Australia.
Many employed people spend virtually all day sitting…and sitting…and sitting. It’s the nature of desk jobs. So what, really, is a person to do? Now there is some alarming news telling us that all this sitting may be doing more damage than just broadening our waists. A study from the Western Australian Institute for Medical Research, University of Western Australia, investigated whether long-term sedentary behavior (in this case, sitting at a desk) might increase the risk for colorectal cancer. The answer was a dismaying “yes”—even for people who get plenty of exercise at other times!
The study, published in American Journal of Epidemiology, took place from 2005 to 2007 and gathered data from 918 colorectal cancer patients and a control group of 1,021 people without colorectal cancer.
Findings: Compared with people who had never performed sedentary work—such as mail carriers, store clerks who stand or walk around the floor all day, construction workers—people who spent 10 or more years in sedentary jobs (i.e., virtually any occupation that requires prolonged periods of sitting) had twice the risk for colon cancer and a 44% increased risk for rectal cancer. The colon cancer risk specifically involved the distal colon, the part of the colon nearest to the rectum. When I contacted the study author, Terry Boyle, PhD candidate and research officer at the Institute, he explained to me that the findings held up regardless of how much physical activity people engaged in when they were away from the office. In fact, the increased cancer risk held true even for those office workers who were the most recreationally active—and even after taking into account people’s diet, alcohol intake and smoking.
Wow, that’s pretty troubling! We asked Boyle why sitting, even if you do exercise, increases cancer risk. He explained that other research suggests that chronic sedentary behavior increases blood glucose levels and decreases insulin sensitivity—both of which are thought to promote development of colorectal cancer—so that is one link that needs to be studied.
Be that as it may, we asked Boyle what observations he has for how people with sedentary jobs might reduce their risk for colorectal cancer. He said that some research has shown that if you break up long periods of sitting simply by standing or walking, it may help counteract the negative effects on metabolic function including changes in glucose and insulin.
Take a break from sitting every 30 minutes, even just to stand up and stretch. Walk to a colleague’s desk or office to talk rather than send an e-mail. Remain standing instead of immediately sliding into the spare chair in your colleague’s office! If you work at home, intersperse vacuuming, carrying laundry up or down stairs, walking to the mailbox or to a nearby shop, or doing 10 minutes of yard chores with seated activity.
Stand up when speaking on the phone—better yet, stand up and pace while on the phone. Follow the guidelines for general good health including going out at lunchtime to take a walk. Remember, these are activities that help to decrease cancer risk in general and, as Boyle noted, provide lots of other physical and mental health benefits as well.