Effect of physical activity as a moderator on the association between perceived racial discrimination and depression in African Americans
Purpose: To evaluate the relationship between perceived racial discrimination and major depressive disorder (MDD) in a sample of African Americans, and then to test if physical activity (PA) can moderate the association if such exists.
Methods: This cross-sectional analysis consists of 775 African Americans (mean age= 45.3) from the Family and Community Health Study (FACHS). Perceived racial discrimination was assessed via the Schedule of Racists events, MDD was diagnosed with the University of Michigan Composite International, self-reported depression scores were assessed with the Mini-Mood and Anxiety Symptom Questionnaire, and PA was measured with two questions created by the FACHS research team. Participants were categorized into tertiles based on their discrimination scores. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs) of having MDD diagnosis within the past 12-months. Linear regression was also used to test the association between racial discrimination, depression, and PA. Participants were further dichotomized into low or high discrimination groups, and physically inactive or active groups to test the combined associations of discrimination and PA with MDD.
Results: Discrimination was found to be positively associated with both self-reported depression in the linear regression [Standardized β= 0.15 (p=<0.01)] and with MDD diagnosis in the logistic regression [OR (95% CI) 3.34 (1.26-8.81)] in the upper tertile compared to the lower tertile] after adjusting for age, education (year), sex, PA, and heavy alcohol use. A stratified analysis was conducted to test the possible effect modification by PA on the association between discrimination and MDD. Among participants who were active (meeting the PA guidelines), participants in the middle and upper categories of discrimination had no increased odds of MDD compared to the lower discrimination group. However, among participants who were inactive, odds of MDD were significantly higher for those in the upper tertile of discrimination compared to the lower tertile [(OR (95% CI) 7.24 (1.54-34.15)] after adjusting for possible confounders.
Although the interaction term was not significant (p=0.18) created from racial discrimination (Lower, Middle, and Upper) and physical activity (Inactive or Active), possibly due to the very small numbers of cases in all six groups (n=2-11) with wide 95% CIs, the above result from the stratified analysis by physical activity levels clearly suggests a possible effect modification by physical activity on the association between racial discrimination and depression in this cohort of African American. However, further studies with larger sample size and more cases of depression are warranted. In the joint analysis, we observed a similar trend suggesting no increased odds of MDD in the high discrimination group if they were active.
Conclusion: Perceptions of racial discrimination show a positive, linear association with MDD in African Americans, and meeting the PA guidelines may reduce the increased odds of depression due to experiencing greater levels of discrimination. However, further prospective studies are needed to confirm the findings from this cross-sectional analyses.