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Arnold School of Public Health


Study establishes link between sedentary time and depressive symptoms in healthy young adults

May 9, 2017 | Erin Bluvas, bluvase@sc.edu 

A study led by Keith Brazendale and published in Progress in Preventive Medicine is the first known research to link sedentary behavior with depressive symptoms in otherwise healthy young adults. Brazendale, who recently graduated from the nation’s No. 1 ranked Ph.D. in Exercise Science program, found that study participants (men in particular) who engaged in higher levels of sedentary time were more likely to experience depressive symptoms. The researchers conclude that a reduction in sedentary time may provide a beneficial, low cost option in the prevention of depressive symptoms.    

Higher amounts of sedentary time have already been associated with increased risk for diabetes, cardiovascular disease, and mortality—regardless of physical activity during non-sedentary periods. Previous studies have also linked time spent being sedentary to depressive symptoms in older adults and adults with chronic diseases. However, there has been little research on the relationship between sedentary time and depressive symptoms in healthy young adults.

Although many young adults today engage in adequate levels of daily physical activity, they are simultaneously capable of accumulating high amounts of sedentary time. Excluding sleep time, adults report more than nine hours of each day is spent being sedentary while awake. These activities include lying down/reclining and sitting (e.g., viewing television, driving, reading).

The health benefits (e.g., reduced risk of chronic diseases, fewer depressive symptoms) of physical activity are well known. However, this area of research suggests that increased amounts of sedentary time may limit the positive effects of physical activity.    

Brazendale’s study lays the groundwork for unearthing the relationship between sedentary behavior and health outcomes for young, active adults by revealing patterns that were previously not available. To overcome the limitations of previous studies’ self-reports of sedentary time, the team used objective measures (i.e., wearable fitness trackers) to determine the activity levels of the study’s 430 participants.  

The present study’s link between sedentary time and depressive symptoms was evident despite the high level of physical activity exhibited by the participants—not only meeting, but surpassing national daily recommendations (i.e., at least 60 minutes of moderate-to-vigorous physical activity per day). These findings suggest that the benefits of physical activity, even high levels of physical activity, may be thwarted due to sedentary behavior.

“This study provides evidence that even if you are sufficiently active on most days of the week, young adults should still look to reduce their daily sedentary time, especially those who sit for long periods of time as part of their job,” says Brazendale. “Taking this lifestyle modification approach to daily life has the potential to prevent detrimental health outcomes, such as depressive symptoms.” 

The authors recommend that future research explores whether depressive symptoms are a behavioral antecedent and/or an outcome of sedentary time. “In other words,” says Brazendale, “are we exhibiting depressive symptoms because we are more sedentary or are we more sedentary because we have depressive symptoms?”

Originally from Scotland, Brazendale graduated with a Ph.D. in Exercise Science with an emphasis in Health Aspects of Physical Activity this month. He plans to pursue a career in academia, which will begin with a postdoctoral fellowship in the Department of Exercise Science this fall. This is the 18th peer-reviewed publication (7th as first author) for the 2016 Breakthrough Scholar and American Kinesiology Association Master’s Scholar Award Winner.


Related:

Four Arnold School graduate students named 2016 Breakthrough Graduate Scholars