Leizi Min, Yicong Cui, Xindong Ma, Longteng Cui
Background/Objectives: Physical activity and dietary inflammatory potential are modifiable correlates of depressive symptoms. We examined whether oral microbial dysbiosis-an imbalance in oral microbial community structure-was associated with an integrated lifestyle profile and depressive symptoms in U.S. adults. Methods: We analyzed 6519 adults aged 20-69 years from NHANES 2009-2012. The Integrated Lifestyle Score combined standardized Dietary Inflammatory Index and leisure-time physical activity; higher scores indicated higher dietary inflammatory potential and lower physical activity. Oral dysbiosis was assessed using a study-specific genus-level log-ratio index. Survey-weighted regression models were fitted, and indirect associations were evaluated using 5000 bootstrap resamples. Results: A less favorable lifestyle profile, characterized by higher dietary inflammatory potential and lower leisure-time physical activity, was associated with higher PHQ-9 scores (β = 0.314, 95% CI 0.113-0.515, p = 0.005), greater odds of clinically relevant depressive symptoms (PHQ-9 ≥ 10; OR = 1.355, 95% CI 1.159-1.584, p < 0.001), and greater oral dysbiosis (β = 0.191, 95% CI 0.050-0.331, p = 0.011). Greater oral dysbiosis was associated with higher PHQ-9 scores (β = 0.101, 95% CI 0.059-0.144, p < 0.001) and greater odds of clinically relevant depressive symptoms (OR = 1.069, 95% CI 1.035-1.105, p < 0.001). The indirect association for continuous PHQ-9 was 0.0188 (bootstrap 95% CI 0.0033-0.0402), representing approximately 6.0% of the total association. Conclusions: A less favorable lifestyle profile was associated with greater depressive symptom burden and oral microbial imbalance. Oral dysbiosis statistically accounted for a small proportion of this association. Given the cross-sectional design and study-specific indices, these findings should be interpreted as exploratory rather than causal.