By Sharon Reynolds
Physical activity reduces the risk of many chronic illnesses and increases the odds of a longer, healthier life. But it hasn’t been clear whether the benefits of exercise differ based on when during their lives people are most active.
Pedro Saint-Maurice, PhD, led a team that looked at data collected from more than 300,000 Americans who participated in the NIH-AARP Diet and Health Study. People aged 50 to 71 were invited to join the study in the mid-1990s. They filled out surveys that categorized their physical activity levels during different life stages: in adolescence, in their 20s and 30s, and during the 10 years before they joined the study. The study tracked participants through 2011 for deaths from any cause as well as deaths specifically from heart disease or cancer.
Saint-Maurice and his team grouped participants into categories based on the physical activity survey data and looked for differences in survival between these groups. The researchers adjusted their analyses to account for influences from people’s existing health problems. Results were published in JAMA Network Open.1
People who were active during adolescence but not later in life gained little benefit compared to people who were never active. Those who exercised for at least 2 hours a week throughout their life were about a third less likely to die during the study than people who were never active.
Unexpectedly, people who stopped exercising in their 20s and 30s but picked the habit up again later (40-61 years of age) seemed to benefit just as much as people who maintained activity across their lifespan. They had similar reductions in the risk of dying from heart disease, cancer, or any cause during the study. These benefits were seen in both men and women, and regardless of participants’ body mass index (or BMI, a ratio of weight to height) during the study.
“Midlife is not too late to start being active,” Saint-Maurice said. “People who have been physically inactive throughout much of their adulthood can gain substantial health benefits by increasing their physical activity.” Participants in the study were mostly white and highly educated. Future studies are needed to see if these findings hold up in ethnically and economically diverse populations.
…Some Is Better Than None
For many people, life is largely sedentary: sitting in the car, sitting at work, even sitting when relaxing at home. A recent study estimated that American adults now spend an average of 11 to 12 hours a day sitting.
Research has shown that long periods of sitting increase the risk of heart disease and death overall. But the amount of activity needed to counter these dangers has been unclear.
To take a closer look, a research team led by exercise physiologist Keith Diaz, PhD, at Columbia University performed a study within the ongoing Reasons for Geographic and Racial Differences in Stroke (REGARDS) project.
The study included almost 8,000 participants aged 45 and older. All participants wore an activity monitor for a week between 2007 and 2013. The device recorded how often they moved while awake and the intensity of their activities. Deaths were tracked through April 2017.
The researchers then used this data to model how, when substituting for sitting, various amounts and intensities of activity affected the risk of death from any cause. Results were published in January in the American Journal of Epidemiology.2 The team found that any amount of activity was better than sitting. People who swap 30 minutes of sitting for 30 minutes of light-intensity activity per day would have a 17% lower risk of death. Light-intensity activities include walking and doing chores that require moving around.
People who swap 30 minutes of sitting for 30 minutes of moderate to vigorous physical activity per day would have a 35% lower risk of death from any cause. These types of activities can include jogging, bicycling, and playing sports. But people didn’t have to move for a full 30 minutes in a row to benefit. Even smaller intervals to break up periods of sitting—including from just 1 to 5 minutes of activity—reduced the risk of death.
The positive effects of movement were seen regardless of age, race, weight, smoking and drinking patterns, or existing health problems. Small amounts of movement mainly benefitted people who didn’t already have an active lifestyle. For people who had a low activity level overall, taking modest activity breaks made a big difference in the risk of death. For people who already had a high level of activity during the day, however, no additional benefit was seen from a little extra movement.
“Our findings underscore an important public health message that physical activity of any intensity provides health benefits,” Diaz said. “If you have a job or lifestyle that involves a lot of sitting, you can lower your risk of early death by moving more often, for as long as you want and as your ability allows.”
Sharon Reynolds is a writer in the Communications Office of the National Institutes of Health in Bethesda, Maryland.
Saint-Maurice PF, Coughlan D, Kelly SP, et al. Association of Leisure-Time Physical Activity Across the Adult Life Course With All-Cause and Cause-Specific Mortality. JAMA Netw Open. 2019;2(3):e190355.
Diaz KM, Duran AT, Colabianchi N, Judd SE, Howard VJ, Hooker SP. Potential Effects of Replacing Sedentary Time With Short Sedentary Bouts or Physical Activity on Mortality: A National Cohort Study. Am J Epidemiol. 2019:188(3):537-544.