The Efficacy of Exercise in Reducing Depressive Symptoms among Cancer Survivors: A Meta-Analysis

INTRODUCTION: The purpose of this meta-analysis was to examine the efficacy of exercise to reduce depressive symptoms among cancer survivors. In addition, we examined the extent to which exercise dose and clinical characteristics of cancer survivors influence the relationship between exercise and reductions in depressive symptoms. METHODS: We conducted a systematic search identifying randomized controlled trials of exercise interventions among adult cancer survivors, examining depressive symptoms as an outcome. We calculated effect sizes for each study and performed weighted multiple regression moderator analysis. RESULTS: We identified 40 exercise interventions including 2,929 cancer survivors. Diverse groups of cancer survivors were examined in seven exercise interventions; breast cancer survivors were examined in 26; prostate cancer, leukemia, and lymphoma were examined in two; and colorectal cancer in one. Cancer survivors who completed an exercise intervention reduced depression more than controls, d(+) = -0.13 (95% CI: -0.26, -0.01). Increases in weekly volume of aerobic exercise reduced depressive symptoms in dose-response fashion (β = -0.24, p = 0.03), a pattern evident only in higher quality trials. Exercise reduced depressive symptoms most when exercise sessions were supervised (β = -0.26, p = 0.01) and when cancer survivors were between 47-62 yr (β = 0.27, p = 0.01). CONCLUSION: Exercise training provides a small overall reduction in depressive symptoms among cancer survivors but one that increased in dose-response fashion with weekly volume of aerobic exercise in high quality trials. Depressive symptoms were reduced to the greatest degree among breast cancer survivors, among cancer survivors aged between 47-62 yr, or when exercise sessions were supervised

Weighted mean effect of exercise modulating depressive symptoms by type of cancer.

<p><b>NOTE:</b> Weighted mean effect size values (<i>d₊</i>) are negative when the exercise intervention was successful in reducing depression compare to standard care.</p><p><i>k</i>, number of studies.</p>a<p>37 studies provided 40 total effect size estimates.</p>b<p>24 studies provided 26 total effect size estimates.</p>c<p>Significance implies rejection of the hypothesis of homogeneity and the inference of heterogeneity.</p

Characteristics related to depressive symptoms change for all cancer survivors.

<p><b>NOTE:</b> Weighted mean effect size values (<i>d₊</i>) are negative when the exercise intervention reduced depression compared to the control group.</p>a<p>Levels represent values of interest of each moderator; in these models, continuous variables were represented in their continuous form; the estimates adjust for the other moderators in the model.</p>b<p><i>d</i>₊ and their 95% CI estimates statistically adjust for the presence of the rest of the moderators in the fixed-effects model, including weekly minutes of exercise×PEDro interaction and their independent linear terms, supervision of exercise, quadratic and linear trends for age, held constant at their means except for the study dimension in question.</p>c<p>β values are standardized.</p>d<p>This is a continuous×continuous interaction. We chose to report PEDro scores of 5 and 10 to highlight the variability along the continuous distribution of PEDro scores, those of very high quality (i.e., 10) versus those of low quality (i.e., 5).</p>e<p>β for interaction. Independent β: weekly aerobic volume, β = −0.09; PEDro methodological score, β = −0.28.</p>f<p>Continuous quadratic trend including linear component.</p

Flow diagram of exercise intervention identification and selection.

<p>Flow diagram of exercise intervention identification and selection.</p