Association between peripheral neutrophil percentage and depressive symptoms among adults with a history of cancer: a population-based NHANES study

Abstract

Depressive symptoms represent a prevalent and burdensome comorbidity among adults with a history of cancer, yet the relationship between routinely available inflammatory markers and depression in this population remains insufficiently characterized, particularly regarding potential nonlinear patterns. This cross-sectional study analyzed data from 4,175 adults with a history of cancer in the National Health and Nutrition Examination Survey (NHANES) to examine the association between neutrophil percentage and clinically significant depressive symptoms, defined as a Patient Health Questionnaire-9 (PHQ-9) score ≥ 10, using multivariable logistic regression, restricted cubic spline (RCS) regression, and piecewise threshold analyses with sequential covariate adjustment. When neutrophil percentage was categorized into quartiles, participants in the third quartile (Q3) exhibited significantly higher odds of depressive symptoms compared with the lowest quartile (adjusted OR = 1.91, 95% CI: 1.11–3.29). RCS regression revealed a significant nonlinear association, with inflection points identified at 50.15% and 64.42%. Within this intermediate range, each 1% increment in neutrophil percentage was associated with a 16.4% increase in depression odds (OR = 1.164, 95% CI: 1.090–1.242, P < 0.001), whereas no significant associations were observed outside this interval. These findings indicate that in adults with a history of cancer, the segmented neutrophil percentage is non-linearly associated with depressive symptoms, and the higher odds of clinically significant depressive symptoms is confined to a specific intermediate range. The identified inflection point should be regarded as an exploratory, study-derived threshold for stratification, and further prospective validation is required.