Increased Vigorous Physical Activity Associated With Lower Mortality

Increased vigorous physical activity is associated with decreased mortality, regardless of sex, age, or body mass index (BMI), according to a study presented at the 54th annual meeting of the American College of Sports Medicine. Previous studies have not clarified the relationship; therefore, this investigation was designed to examine the observed inverse relationship between physical activity and mortality in a large cohort, according to presenter Michael Leitzmann, MD, an epidemiologist at the National Cancer Institute, in Bethesda, Maryland.
A total of 559,898 American men and women, aged 50 to 71 years, were followed for 10 years (from 1995 to 2005). A self-administered questionnaire was used to assess baseline physical activity. Deaths from any cause were confirmed with the Social Security Administration Death Master File and the National Death Index Plus.
During the 5,094,780 person-years of follow-up, 20,517 women and 46,381 men died. The researchers compared those who rarely engaged in vigorous physical activity (defined as 20 minutes/session, accepted as minimum duration for health benefits) with those who engaged in 20 minutes of vigorous physical activity 1 to 3 times per month, 1 to 2 times per week, 3 to 4 times per week, and 5 or more times per week. For women, the relative risks of mortality (95% confidence interval) were 0.76, 0.72, 0.65, and 0.63, respectively; for men, relative risks were 0.76, 0.68, 0.61, and 0.57. The inverse association between vigorous physical activity and mortality did not change with sex, age, or BMI, but for those with a history of chronic disease, the association was stronger in the first 5 years of follow-up than in the second 5 years. The study had to address reverse causality (effect before cause), because chronic disease present at the time of physical-activity assessment can result in a positive association between decreased physical activity and death.
Dr. Leitzmann commented: "One of the corrections one can undertake to address that potential bias is to not count people who die early during follow-up. You disregard the early years of follow-up. We only looked at deaths that occurred starting at year 6 and we found an association that was very similar to the initial years of follow-up. That led us to conclude that although these relationships were not entirely identical, they were still very similar; we could then safely conclude that physical activity is associated inversely with the risk of mortality in this cohort."
Edward McFarland, MD, professor of orthopedics surgery at Johns Hopkins Hospital in Maryland, said "this is an interesting study because it shows that, for people who don't have cardiac diseases, if you exercise, you're going to have decreased morbidity and mortality. This effect is the same regardless of age, sex, and BMI, indicating that just about anyone who becomes active will see a positive effect."