MedicalResearch.com Interview with:
I-Min Lee, MD, ScD
Professor of Medicine, Harvard Medical School
Professor of Epidemiology, Harvard T.H. Chan School of Public Health
Brigham and Women’s Hospital
Boston, MA 02215
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: The fact that physical activity lowers the risk of premature mortality is not a new fact – we have many studies showing this. However, previous studies have primarily relied on self-reported physical activity, and self-reports tend to be imprecise. Based on these self-report studies, we know that physical activity is associated with a 20-30% reduction in mortality rates. And, these self-report studies also have focused on moderate-to-vigorous intensity physical activity, since they are more reliably reported than lighter intensity activity. We have little information on whether light-intensity activities (e.g., light household chores, very slow walking such as when strolling and window shopping) are associated with lower mortality rates.
We now have “wearables” – devices that can more precisely measure physical activity at low (as well as higher) intensities, and sedentary behavior. The present study, conducted between 2011 and 2015, investigated a large cohort of older women (n=16,741; mean age, 72 years) who were asked to wear these devices for a week – thus, providing detailed physical activity and sedentary behavior measures. During an average follow-up of about two-and-a-half years, 207 women died. The study confirmed that physical activity is related to lower mortality rates.
What is new and important is how strong this association is when we have more precise measures of physical activity – the most active women had a 60-70% reduction in mortality rates, compared with the least active, during the study. For context, non-smokers have about a 50% risk reduction, compared to smokers, which is why patients (and doctors) should pay attention to being physically active.
The reduction was seen with moderate-to-vigorous intensity activity (e.g., brisk walking), but not with light-intensity activity. Sedentary behavior was also not independently related to higher mortality rates. These findings support current physical activity guidelines, such as those from the federal government and the American Heart Association, that recommend moderate-to-vigorous intensity physical activity.
Note that that the present study examined only mortality (we continue to follow women for other outcomes), so light-intensity activity may indeed be helpful for other outcomes not reported here – e.g., function, well-being, good quality of life, etc. We intend to report on other health outcomes in the future.
MedicalResearch.com: What should clinicians and patients take away from your report?
Response: Physical activity is extremely important for health – try to incorporate physical activity into daily life; e.g., park your car a little further from your destination and walk the rest of the distance; walk or bicycle when doing errands, instead of driving. The study also shows a “dose-response” relation between physical activity and mortality rates – that is, anything is better than nothing, and more is better than a little.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: As noted above, we are interested in other health outcomes besides mortality – what is the association between better measures (using devices) of physical activity, at different intensities, or sedentary behavior, and these other health outcomes?
MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.
Accelerometer-Measured Physical Activity and Sedentary Behavior in Relation to All-Cause Mortality: The Women’s Health Study
I-Min Lee, Eric J. Shiroma, Kelly R. Evenson, Masamitsu Kamada, Andrea Z. LaCroix, Julie E. Buring
Originally published November 6, 2017
Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.