Effects of physical exercise on plasma levels of brain-derived neurotrophic factor and depressive symptoms in elderly women--a randomized clinical trial.

OBJECTIVES: To investigate the effect of 2 standardized exercise programs, muscle strength exercises (SE) and aerobic exercises (AE), on the plasma levels of brain-derived neurotrophic factor (BDNF) and depressive symptoms in 451 elderly women.

DESIGN: A randomized controlled trial.

SETTING: Belo Horizonte/MG-Brazil.

PARTICIPANTS: Community-dwelling older women (N=451; age, 65-89y).

INTERVENTION: The participants were divided into 2 groups: SE and AE. Both protocols lasted 10 weeks, and 30 sessions (1-h sessions) in total were performed 3 times a week under the direct supervision of physical therapists.

MAIN OUTCOME MEASURES: Plasma levels of BDNF (enzyme-linked immunosorbent assay) and depressive symptoms (Geriatric Depression Scale).

RESULTS: There was a significant difference for BDNF plasma levels between the SE and AE groups (P=.009). Post hoc analysis revealed a pre-post intervention difference in BDNF levels only for the SE group (P=.008). A statistically significant difference was found for the pre- and postintervention Geriatric Depression Scale scores in both groups (P=.001), showing that the effects of both exercise protocols were comparable regarding depressive symptoms (P=.185).

CONCLUSIONS: The present findings have demonstrated the positive effect of muscle strengthening and aerobic intervention on depressive symptoms in community-dwelling elderly women. Interestingly, only SE significantly increased the plasma levels of BDNF in our sample. The positive effects of physical exercise on depressive symptoms in the elderly were not mediated by BDNF.