Sleep Duration and the Association Between Systemic Inflammatory Response Index and Depressive Symptoms Among...

ObjectiveThis study examined the association between the Systemic Inflammatory Response Index (SIRI) and depressive symptoms among emerging adults aged 18-25 years, with an emphasis on the indirect role of sleep duration.MethodThis cross-sectional study utilized data from the National Health and Nutrition Examination Survey (NHANES) 2005-2023. A total of 6563 participants with complete data on the Patient Health Questionnaire-9 (PHQ-9), complete blood count parameters for SIRI calculation, and self-reported sleep duration were included. Depressive symptoms were defined as a PHQ-9 score ≥10. Weighted multivariable logistic regression, restricted cubic spline analysis, and bootstrap-based exploratory mediation analysis (n = 1000) were employed.ResultsOverall, 604 participants (9.2%) met the criteria for depressive symptoms. After full adjustment for covariates, SIRI demonstrated a significant positive association with depressive symptoms (Model 4: OR = 1.16, 95% CI = 1.02-1.33, P = 0.03). Participants in the highest SIRI quartile (Q4) exhibited 33% higher odds of depressive symptoms compared to the lowest quartile (Q1) (OR = 1.33, 95% CI = 1.09-1.61, P = 0.005). No significant nonlinearity was observed (P for nonlinearity = 0.066). Exploratory mediation analysis revealed a negative indirect effect through sleep duration (β = -0.009), accounting for approximately 6.2% of the total effect.ConclusionsHigher SIRI levels were associated with increased odds of depressive symptoms among emerging adults. Sleep duration played a modest suppressor role in this relationship, suggesting complex interactions between inflammation, sleep, and mental health warranting further investigation through prospective studies.