Evaluating the timing of differences in activity related to depression symptoms across adulthood in the United States

Relative activity deficits found in people with (verses without) depression symptoms/disorders may accumulate uniformly throughout the day, or they may tend to be expressed at specific times. Evidence for the latter would suggest times when behavioral approaches are most needed to reduce depression and its health consequences.

We performed a secondary-data analysis of participants who contributed valid accelerometer data at the 2005-2006 National Health and Nutrition Examination Survey (n=4390). Participants were categorized according to the Patient Health Questionnaire-9 standard cut-point of ≥10 (i.e., people with versus without clinically significant depression symptoms). Average levels of accelerometer-measured activity in two-hour bins were the dependent variable in mixed models testing if the relationship between depression status and activity level differed by time of day; and if any such relations varied by age group (18-29 years, 30-44 years, 45-59 years, and 60+ years).

In adults over the age of 30, people with depression symptoms had generally lower levels of activity across the day, but these effects were most markedly pronounced in the morning hours. We found no differences in activity levels associated with prevalent depression symptoms among people 18-30 years of age.

Core aspects of depression pathophysiology that produce these different activity patterns and confer their effects on mood were not measured.

In adults 30 years and older, efforts to ameliorate relative activity deficits associated with depression may benefit from considering the apparently outsized role of inactivity that occurs in the morning.