The association between neutrophil percentage-to-albumin ratio (NPAR) and depression among US adults: a cross-sectional study

Inflammation plays an important role in depression, and the neutrophil-to-albumin ratio (NPAR) is a cost-effective and readily available novel biomarker of inflammation. The association between NPAR and depression is unclear; therefore, to assess the relationship between NPAR and depression, we conducted a cross-sectional study of 33,768 participants ≥ 18 years of age from the 2005-2018 NHANES database. NPAR was calculated as Neutrophil percentage (in total WBC count) (%) × 100/Albumin (g/dL). Multivariate logistic regression models were used to test the independent association between NPAR and depression, adjusting for demographic factors, education, smoking status, alcohol consumption, hypertension, diabetes mellitus, body mass index, the ratio of income to poverty, and history of cardiovascular disease. Results showed that NPAR was significantly and positively associated with depression. When NPAR were analyzed as a categorical variable, there was a 20% increase in the prevalence of depression in the quartile with the highest NPAR compared to the quartile with the lowest NPAR (OR 1.20[95% CI 1.06, 1.36]). Smoothed curve fitting and threshold effect analyses also showed a positive association between NPAR and depression, with an inflection point for threshold and saturation effects of 12.65. NPAR was positively associated with the likelihood of developing depression when NPAR > 12.65 (OR 1.06[95% CI 1.04, 1.09]). The results of subgroup analyses and interaction tests indicated that smoking status had a significant effect on the relationship between NPAR and depression (P < 0.05). Our study reveals a positive association between NPAR levels and depression, suggesting that higher NPAR levels are associated with an increased likelihood of developing depression.