From Medscape Medical News
Pam Harrison
March 11, 2010 (Savannah, Georgia) — Higher levels of physical activity objectively measured by an accelerometer are strongly associated with lower levels of depressive symptoms and a lower prevalence of depressive disorders, according to an analysis of the 2005 to 2006 National Health and Nutrition Examination cohort and presented here at the American Association for Geriatric Psychiatry 2010 Annual Meeting.
Chad Rethorst, PhD, University of Rochester Medical Center, New York, and colleagues found that moderate physical activity as measured by an accelerometer totaling only 12 minutes a day was still significantly associated with lower levels of depressive symptoms (P < .0001) and a lower prevalence of depressive disorders (P = .003). An accelerometer gives a reading of movement intensity.
There was also a trend toward lower levels of depressive symptoms and a lower prevalence of depressive disorders in those who met American College of Sports Medicine (ACSM) recommendations for activity levels. Somewhat paradoxically, there was no association between sedentary behaviors and depressive symptoms or disorders, possibly because the cohort was extremely sedentary overall.
"Participants were only wearing an accelerometer for 1 week, so you have an idea of how much they did during that 1 week, but you don’t know how representative that week is of what they are doing on a more regular basis," Dr. Rethorst told Medscape Psychiatry. "Still, what I found most interesting in this analysis is the relationship between physical activity and depression that we expected to find and which has been previously reported in older adults."
Exercise Good for Other Comorbidities
A total of 1103 adults (mean age, 67.6 years) were included in the analysis. Depressive symptoms were measured by the Patient Health Questionnaire 9 (PHQ-9) total score, and subjects were categorized into subjects with major or minor depression or nondepressed subjects based on their PHQ-9 responses.
Physical activity was quantified in 3 ways — mean counts per minute, amount of time spent in 3 levels of activity, and physical activity levels meeting ACSM recommendations.
Based on PHQ-9 scores, 92.6% of the cohort was categorized as nondepressed, 5.6% had minor depression, and 1.7% had major depression. Measured in minutes, participants also spent 276 minutes a day in sedentary behavior, 12 minutes a day in moderate physical activity, and 0.25 minute a day in vigorous physical activity.
Time spent in vigorous activity was not associated with depressive symptoms or disorders because the amount of time the cohort spent in vigorous physical activity was extremely limited, said Dr. Rethorst. The association between those who adhered to ACSM recommendations for physical activity was also nonsignificant, very likely because few individuals met these requirements.
"When you are looking at depression in older adults, you are usually dealing with a host of comorbid medical illnesses, and what’s good about exercise is that it has the potential to not only affect depressive symptoms, but it may influence some of the other medical comorbidities that often exist in depressed patients as well," Dr. Rethorst said.
Chicken or the Egg?
Ellen Whyte, MD, University of Pittsburgh Medical Center, Pennsylvania, agreed that the analysis showed that the more sedentary people tended to be more depressed. "However," she told Medscape Psychiatry, "it doesn’t answer the chicken or the egg question, which is, are people more sedentary because they are depressed or does a sedentary lifestyle contribute to the depression? It could probably go both ways, and it is probably more complex than just saying it’s one causing the other," she said.
On the other hand, there is a growing body of literature that indicates that exercise seems to have a therapeutic effect on older people with depression.
"This suggests that maybe those individuals who are exercising more vigorously are actually giving themselves a prophylactic antidepressant through their exercise. Although once again in this study, we cannot rule out the possibility that being sedentary was a symptom of depression," she added.
Dr. Rethorst and Dr. Whyte have disclosed no relevant financial relationships.
American Association for Geriatric Psychiatry (AAGP) 2010 Annual Meeting: Abstract EI 9. Presented March 7, 2010.
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