Friday, September 25, 2015 Study: Physical Activity Knocks Back Cancer Mortality Rates A meta-analysis of studies involving over 3 million participants has concluded that not only does physical activity (PA) reduce cancer mortality, but the mortality risk decreases as the amount of PA goes up—and the effects seem to be even greater for individuals who have been diagnosed with the disease. In a study published online in the British Journal of Sports Medicine (abstract only available for free), researchers analyzed results of 71 studies focused on the relationship between PA and cancer mortality. The studies were conducted in North America, Europe, and Asia, and involved both the general population (36 studies) and research focused solely on cancer survivors (35). Authors of the current study were particularly interested in finding out whether the World Health Organization (WHO) recommendations for PA were sufficient to make a difference in mortality rates. Those recommendations call for a minimum of 2.5 hours per week (h/week) of moderate-intensity PA. The answer: yes, and then some. Researchers found out that in the overall population, following the minimum recommendations led to a 13% reduction in cancer mortality. Those benefits accrued rapidly at the lower end of the scale, with an approximate 2% reduction in cancer mortality for every metabolic equivalent of task (MET) h/week up to 7.5 (7.5 MET h/week being roughly equivalent to 2.5 h/week of moderate-intensity PA). After that, cancer mortality rates continued to drop, albeit at a rate closer to 1% for every 10 MET h/week over the 7.5 mark. For cancer survivors, the benefits were even more dramatic. "Basically, cancer survivors undertaking the highest level of physical activity had a 22% reduction in cancer mortality," authors write. In a deeper analysis of breast cancer survivors, researchers pinpointed the differences. "Compared with no recreational activity, 5, 10, 15, and 20 MET-h/week of prediagnostic [PA] reduced breast cancer mortality by 24%, 28%, 29%, and 30% respectively," they write. "Meanwhile, breast cancer mortality reduced by 24%, 32%, 39%, and 40% when individuals participated in the [same levels of MET-h/week] after diagnosis." This phenomenon—larger reductions in mortality from physical activity in individuals after a cancer diagnosis—is consistent with other studies, according to the authors, who speculate that "a possibility is that individuals who participate in physical activity after a cancer diagnosis may be motivated to change their behavior and adopt a healthier lifestyle." As for the WHO recommendations, researchers believe that the 2.5 h/week of moderate intensity PA guideline is "generally sufficient for reducing cancer mortality." Beyond that, authors see even more positive relationships. "Our study displays that [PA] performed before or after cancer diagnosis is related to reduced mortality rates among cancer survivors," they write. "Thus, we infer that [PA] after a cancer diagnosis may result in significant protection among cancer survivors." Research-related stories featured in PT in Motion News are intended to highlight a topic of interest only and do not constitute an endorsement by APTA. For synthesized research and evidence-based practice information, visit the association's PTNow website. Encouraging healthy, active lifestyles is central to the physical therapy profession's ability to transform society. Keep up with the latest resources at APTA's Prevention, Wellness, and Disease Management webpage.