Physical Activity Linked to Decrease in Mortality Risk

December 12, 2007 — Engaging in physical activity for at least 3 hours per week was associated with a decrease in mortality risk of 27%, according to the results of a prospective study reported in the December 10/24 issue of the Archives of Internal Medicine.
"The Office of the US Surgeon General (OSG), the Centers for Disease Control and Prevention (CDC), and the American College of Sports Medicine (ACSM) all endorse a minimum of 30 minutes of moderate activity on most days of the week, an amount and intensity of activity that is feasible for most Americans," write Michael F. Leitzmann, MD, DrPH, from the National Cancer Institute in Bethesda, Maryland, and colleagues. "Whether national physical activity recommendations are related to mortality benefit is incompletely understood."
The investigators evaluated the relationship between mortality and adherence to physical activity guidelines in 252,925 adults aged 50 to 71 years who were enrolled in the National Institutes of Health–American Association of Retired Persons (NIH-AARP) Diet and Health Study. Two self-administered baseline questionnaires were used to estimate physical activity.
There were 7900 deaths during 1,265,347 person-years of follow-up. Compared with inactivity, moderate activity (at least 30 minutes on most days of the week) or vigorous exercise (at least 20 minutes 3 times per week) was associated with a decreased mortality risk of 27% (relative risk [RR], 0.73; 95% confidence interval [CI], 0.68 - 0.78) and 32% (RR, 0.68; 95% CI, 0.64 - 0.73), respectively.
Participants meeting both recommendations of physical activity had dramatic reductions in mortality risk, both for the overall sample (RR, 0.50; 95% CI, 0.46 - 0.54) and in subgroups, including smokers (RR, 0.48; 95% CI, 0.44 - 0.53) and nonsmokers (RR, 0.54; 95% CI, 0.45 - 0.64), normal-weight (RR, 0.45; 95% CI, 0.39 - 0.52), and overweight or obese individuals (RR, 0.48; 95% CI, 0.44 - 0.54), and those with 2 hours per day (RR, 0.53; 95% CI, 0.44 - 0.63) and more than 2 hours per day of watching television or videos (RR, 0.50; 95% CI, 0.45 - 0.55). Taking part in physical activity at less than recommended levels was also associated with decreased mortality risk (RR, 0.81; 95% CI, 0.76 - 0.86).
"Following physical activity guidelines is associated with lower risk of death," the study authors write. "Mortality benefit may also be achieved by engaging in less than recommended activity levels."
Limitations of the study include self-reported information on physical activity causing possible misclassification and inability to adjust for a family history of cardiovascular disease.
"Our findings suggest that engaging in any physical activity by those who are currently sedentary represents an important opportunity to decrease the risk of mortality," the study authors conclude.
The Intramural Research Program of the NIH National Cancer Institute supported this study. One of the study authors has obtained funding. The other study authors have disclosed no relevant financial relationships.
Arch Intern Med. 2007;167:2453-2460.