Technological advancements in the past 60 years have led to an increasingly sedentary lifestyle. Changes in transportation, communication, the workplace and domestic entertainment have fostered environments in occupational, home and social settings that now demand or encourage sedentary behavior throughout most of the day. In recent years, we have become more aware of the negative impact of a sedentary lifestyle on health and longevity. Research shows that being sedentary for long periods of time increases risk for diabetes, heart disease, some cancers and death. However, less is known about the relationship between sedentary behavior and quality of life outcomes such as physical function. As we age, maintaining mobility and preventing disability are keys to living independently; thus, identifying modifiable risk factors to target to prevent loss of physical function is critical to support healthy aging.
Current studies on the relationship between sedentary behavior and declines in physical function have yielded mixed results. In addition, little is known about what type of physical activity should replace sedentary time to prevent declines in physical function. Our study, published in Medicine & Science in Sports & Exercise®, sought to address these questions. We analyzed data from a U.S. national study of over 5,000 middle-aged and older adults. In the study, a physical activity monitor was used to measure a person’s movements and sedentary time throughout the day for one week. We then measured the participants’ physical function an average of 3.6 years later.
We found that greater time spent sedentary was linked to poorer physical function at follow-up. For example, participants who were more sedentary performed slower on both timed walk and chair-stand tests, and self-rated their physical function to be poorer. But we found that sedentary behavior didn’t have the same effect for people who engaged in regular moderate- or vigorous-intensity physical activity (i.e., exercise). Sedentary behavior was not linked to poorer physical function at follow-up for people who engaged in ~50 minutes or more per week of exercise. In other words, modest amounts of regular exercise may protect against the harms of sedentary behavior as it relates to declines in physical function.
Using the collected data, we also estimated how substituting time spent sedentary with time being physically active would affect physical function at follow-up. As expected, we found that replacing 30 minutes of sedentary time with moderate- or vigorous-intensity physical activity would yield the greatest improvements in physical function. But notably, we also found that swapping the same amount of sedentary time for light-intensity physical activity also would yield improvements in physical function. This finding underscores an important public health message: Any physical activity, no matter how intense, provides health benefits.
Ultimately, our findings show that a sedentary lifestyle may be linked to declines in physical function over time. However, physical activity of any intensity may protect against these declines. While regular exercise still provides the best “bang for your buck,” our findings are good news for people who may not have the time, ability or desire to exercise. The road to an active lifestyle that promotes healthy aging is more accessible and achievable than we thought.
Keith Diaz, PhD, is an ACSM Certified Exercise Physiologist® and the Florence Irving Associate Professor of Behavioral Medicine at Columbia University Medical Center. Dr. Diaz is director of the Exercise Testing Laboratory and Wearable Device Reading Center at the Center for Behavioral Cardiovascular Health. He conducts scientific research to elucidate the role of prolonged sedentary behavior in the development of chronic diseases, with a specific focus of optimizing feasible, sustainable and cost-effective guidelines for reducing prolonged sitting. Dr. Diaz is a member of ACSM and serves on the Pronouncements Committee.
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