Physical exercise appears to improve executive functions in patients with depression, according to Kubesch and colleagues in the September 2003 issue of the Journal of Clinical Psychiatry. However, it is not clear whether physical exercise prevents affective disorders. In the May 28, 2010, issue of BMC Medicine, Rothon and colleagues reported that a change in physical activity was not associated with depressive symptoms in adolescents at 2-year follow-up.
This prospective cohort study by Åberg and colleagues assesses whether cardiovascular fitness at age 18 years in a male population is associated with a future risk for affective disorders and whether muscle strength plays a role.
STUDY SYNOPSIS AND PERSPECTIVE
Good physical fitness at age 18 years is associated with a reduced risk for serious depression later in life, a new study shows.
"Lower cardiovascular fitness, independent of muscle strength, at age 18 years was associated with increased risk of serious depression in adulthood, even 31 to 40 years later, although no such association could be shown for bipolar disorder," lead author Maria A. Åberg, MD, PhD, Sahlgrenska Academy, University of Gothenburg, in Sweden, toldMedscape Medical News.
"These results strengthen the theory of a cardiovascular contribution to the etiology of depression," she added.
The results, which are from a study that included more than 1 million Swedish men, was published online June 14 in the British Journal of Psychiatry.
Dr. Åberg and her team have been studying brain plasticity in animal models for many years; the results from those studies, as well as intervention studies, suggest that physical exercise may improve cognition and mood in persons with an already established depression.
"A proposed mechanism is that physical exercise could reverse the reduced neuronal plasticity that is observed in both depression and bipolar disorders. Previous human studies have shown that a sedentary lifestyle increases the risk of depression, but most of these have been based on interviews with adults and the results have been inconclusive, and we felt that there was a real need for a large study with long follow-up times and objective measures of physical performance," Dr. Åberg explained.
The researchers carried out a prospective cohort study of all Swedish men born between 1950 and 1987 with no history of mental illness who were enlisted for mandatory military service at the age of 18 years.
When enlisting, all 1,117,292 men were given extensive physical and psychological examinations, including tests of their cardiovascular and muscle fitness.
The men were followed between 1969 and 2008. The researchers used data from the Swedish National Hospital Discharge Register to see how many had received inpatient treatment for depression.
The study showed that the men who performed poorly on the cardiovascular fitness tests at age 18 years were at greater risk of being hospitalized with depression in later life.
After controlling for factors that included body mass index, conscription test center, and familial factors, the hazard ratio (HR) associated with lower cardiovascular fitness at age 18 for serious depression in adulthood was 1.96 (95% confidence interval [CI], 1.71 - 2.23).
There was no such association found for bipolar disorder (HR, 1.11; 95% CI, 0.84 - 1.47).
"Doctors can tell their teenage patients and their parents that the brain needs two types of training, both cognitive challenges and physical exercise," Dr. Åberg said.
She added that she hoped politicians and school administrators would give sport a higher status and also more resources. "Moreover, targeting specific high-risk groups for developing depression with cardiovascular training early in life is of high importance."
Incremental Step Forward
Alan J. Gelenberg, MD, Shively/Tan Professor and chair, Department of Psychiatry, Penn State University, Hershey, Pennsylvania, called this an "exciting" study when commenting on it for Medscape Medical News.
"When I saw this study, I shared it with a couple of the researchers in my own department, because it's a very nice incremental step forward," he said.
"In terms of linking exercise, physical fitness, and mood disorders, it is a puzzle that we don't have the full picture. This is another piece, and given the fact that the study deals with more than a million human beings, it does give us some ability to dissect apart important variables," Dr. Gelenberg said.
"Now we are having an epidemic of lack of fitness, obesity, diabetes, and cardiovascular problems, but we are learning in my field that these problems are not just restricted to the heart and the endocrine and vascular system; it also seems to have effects on brain health," he said.
Dr. Åberg and Dr. Gelenberg have disclosed no relevant financial relationships.
Br J Psych. Published online June 14, 2012. Abstract
Lower cardiovascular fitness in 18-year-old men is linked with an increased risk for serious depression in adulthood (HR, 1.96) but not bipolar disorder.
The link between lower cardiovascular fitness in 18-year-old men and the risk for serious depression in adulthood is independent of muscle strength.