Lymphocyte-based inflammatory biomarkers during the postpartum period and postpartum depression symptoms in U.S....

Postpartum depression (PPD) has multiple cascading negative effects on maternal and infant health. Inflammation is a potential factor for the development of PPD. However, lymphocyte-based inflammatory biomarkers, including platelet-to-lymphocyte ratio (PLR), neutrophil-lymphocyte ratio (NLR) and monocyte-lymphocyte ratio (MLR), and PPD remains understudied, especially in U.S. women.

We conducted a cross-sectional study based on the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2020 pre-pandemic data. Based on demographics and reproductive questionnaires, two strategies were employed to include eligible postpartum women. PPD symptoms were assessed using the PHQ-9 questionnaire. Weighted logistic regression models, restricted cubic spline (RCS) models, eXtreme Gradient Boosting (XGBoost) machine learning (ML) model, subgroup analysis and sensitivity analyses were performed to analyze the relationships between these biomarkers and PPD symptoms.

A total of 1,361 postpartum women within the 3-year postpartum period based on strategy 1, and 762 women ranges from one to twenty-eight months postpartum based on strategy 2 were included in analyses. After adjusted for all covariates, PLR during the postpartum period was significantly associated with the reduced risk of PPD symptoms based on both strategies (OR = 0.49, 95% CI: 0.26-0.94, P = 0.033; OR = 0.30, 95% CI: 0.15-0.60, P < 0.001). There was a non-linear relationship between PLR and the risk of PPD symptoms (P-non-linear = 0.011, P-non-linear = 0.001). ML revealed PLR as one important variable for PPD symptoms. Interestingly, postpartum time modified the association between PLR and PPD symptoms (P for interaction = 0.026). The association was significant in women within 12 months postpartum (OR = 0.23, 95% CI: 0.11-0.49, P < 0.001) but not in women with beyond 12 months postpartum. Sensitivity analyses validated the robustness of our findings.

PLR during the postpartum period is an independent risk factor for PPD symptoms in U.S. women, exhibiting its potential as a novel marker for PPD symptoms.