Evidence is clear that physical activity lowers the risk of getting colorectal cancer. But for those who are diagnosed with this cancer, a new study suggests that survivors who spend more time walking and less time sitting – both before and after diagnosis – may have a longer life.
The study was published in the Journal of Clinical Oncology this week.
Study researchers used data from participants who were part of a large cancer prevention study that started in 1992. Fifteen years later, almost 2,300 of the participants were diagnosed with colorectal cancer. When they entered the study and after the cancer diagnosis, participants filled out questionnaires about how active they were and how much time they spent sitting per week.
After following the survivors for an average of almost seven years, the researchers grouped participants into activity levels both before and after their diagnosis. Those who were the most active before their diagnosis had a 28 percent lower risk of death from any cause compared to those who were the least active. People who were the most active did the equivalent of at least 150 minutes of brisk walking per week — 8.75 or more metabolic equivalents (METs); those in the least active group did fewer than 3.5 MET hours per week, less than about 60 minutes of walking.
For physical activity after diagnosis, the link between activity and reduced risk of death was even stronger. Those who were the most active had about a 40 percent reduced risk of premature death compared to those who were the least active.
Then the researchers looked at sitting time, which emerging studies are linking to many indicators of disease risk, independent of physical activity. Both before and after diagnosis, sitting for six or more hours a day linked to a higher risk of death overall during the course of the study compared to those who sat fewer than three hours a day. When focusing on only death from colorectal cancer, sitting for long periods of time after the cancer diagnosis linked to about a 60 percent higher risk of dying from the cancer during the course of the study.
Both with physical activity and sitting time, the study mirrors previous findings suggesting that survivors should avoid inactivity, aiming to eventually meet the government’s physical activity recommendations of 150 minutes moderate intensity aerobic exercise each week.