Joint Effect of Inflammatory Dietary Patterns and Physical Activity on the Risk of Depressive Symptoms: A Nation-Wide Cross-Sectional Study.

Purpose: Depression is a major global public health concern. Diet and physical activity are major modifiable lifestyle factors associated with depression; however, their joint effects have not been fully addressed. This cross-sectional study aimed to quantitatively examine the interaction between physical activity and inflammatory nutrients in depression and utilized Bayesian kernel machine regression (BKMR) models to compare the effects of inflammatory nutrients on depression in individuals with and without physical activity.

Materials and methods: The inflammatory diet was assessed using the dietary inflammatory index (DII), while physical activity levels were measured using the Global Physical Activity Questionnaire, with sufficient physical activity defined as achieving 600 metabolic equivalent task minutes per week. Depression was defined as a 9-item Patient Health Questionnaire score of ≥10. We used multiple logistic regression and BKMR models to investigate the associations between the DII and depression, with all models adjusted for covariates.

Results: A total of 4110 participants from the 2020 Korea National Health and Nutrition Examination Survey were included in this study. Notably, participants with higher total DII scores were more likely to have depressive symptoms, and the additive interaction between insufficient physical activity and inflammatory nutrients was attributed to a 36% risk of depression. Moreover, BKMR analyses showed that individuals with insufficient physical activity exhibited a greater risk of depression posed by pro-inflammatory dietary patterns and did not benefit from anti-inflammatory dietary patterns with regard to the risk of depression.

Conclusion: Comprehensive plans for diet control and increased physical activity are essential to help prevent depression.