In a study that investigated objective measures of sedentary behavior and cancer mortality, researchers found that greater inactivity was independently associated with a higher risk of dying from cancer. An accelerometer was used to measure physical activity, rather than relying on participants to self-report their activity levels. These findings were reported by Gilchrist et al in JAMA Oncology.

“This is the first study that definitively shows a strong association between not moving and cancer death,” said lead study author Susan Gilchrist, MD, Associate Professor of Clinical Cancer Prevention at The University of Texas MD Anderson Cancer Center, in a statement. “Our findings show that the amount of time a person spends sitting prior to a cancer diagnosis is predictive of time to cancer death.”

Study Design

The study involved a cohort of participants from the nationally representative REGARDS study, which recruited more than 30,000 adults older than age 45 in the United States between 2003 and 2007 to study long-term health outcomes.

To measure sedentary behavior, 8,002 REGARDS participants who did not have a cancer diagnosis at study enrollment wore an accelerometer on their hip during waking hours for 7 consecutive days. The accelerometer data were gathered between 2009 and 2013.

Results

After a mean follow-up of 5 years, 268 participants died of cancer. The most sedentary individuals had an 82% higher risk of cancer mortality compared to the least sedentary individuals. Longer duration of sedentary behavior was independently associated with a greater risk of cancer death.

Researchers also found that replacing 30 minutes of sedentary time with physical activity was associated with a 31% lower risk of cancer death for moderate-intensity activity, such as cycling, and an 8% lower risk of cancer death for light-intensity activity, such as walking.

“Conversations with my patients always begin with why they don’t have time to exercise,” said Dr. Gilchrist, who also leads MD Anderson’s Healthy Heart Program. “I tell them to consider standing up for 5 minutes every hour at work or taking the stairs instead of the elevator. It might not sound like a lot, but this study tells us even light activity has cancer survival benefits.”

The study also found that engaging in either light or moderate to vigorous physical activity made a difference in mortality risk. Investigators assessed sedentary time, light physical activity, and moderate to vigorous physical activity in the same model, and found that light, moderate, and vigorous physical activity—not sedentary behavior—remained significantly associated with cancer mortality.

“From a practical perspective, this means that individuals who replaced either 10 to 30 minutes of sedentary time with either light physical activity or moderate to vigorous physical activity had a lower risk of cancer mortality in the REGARDS cohort,” said Dr. Gilchrist.

The study had several limitations, including a potentially healthier participant sample compared to the full REGARDS cohort and a lack of site-specific cancer data, including type of tumor and treatment.

“Our findings reinforce that it’s important to ‘sit less and move more’ and that incorporating 30 minutes of movement into your daily life can help reduce your risk of death from cancer,” concluded Dr. Gilchrist. “Our next step is to investigate how objectively measured sedentary behavior impacts site-specific cancer incidence, and if [sex] and race play a role.”

Disclosure: The research was supported by several institutes of the National Institutes of Health. For full disclosures of the study authors, visit jamanetwork.com.