The association between weight-adjusted-waist index and serum neurofilament light chain: Results from NHANES 2013 to 2014

Neurofilament light chain (NfL) is an important biomarker for neuronal damage, widely used in the study of neurodegenerative diseases. The weight-adjusted-waist index (WWI), as a measure of abdominal obesity, is closely related to metabolic diseases. However, the association between WWI and NfL has not been systematically investigated. This study aimed to evaluate the association between WWI and serum neurofilament light chain (sNfL) levels. This study was based on data from the 2013 to 2014 cycle of the National Health and Nutrition Examination Survey, including 1964 adult participants. Multiple linear regression models were used to analyze the association between WWI and sNfL, adjusting for covariates such as sex, age, race, and lifestyle factors. Restricted cubic spline models were applied to assess potential nonlinear relationships. Subgroup analyses were conducted for sex, age, race, education level, smoking, drinking, depression, and diabetes. WWI was positively correlated with sNfL. In the unadjusted Model 1, the regression coefficient was 0.18 (95% CI: 0.15-0.22, P < .001); after adjusting for all covariates, the association remained significant (β = 0.04, 95% CI: 0.002-0.07, P = .04). The restricted cubic spline analysis revealed a U-Shaped nonlinear relationship between WWI and sNfL, with a threshold inflection point at 10.38 cm/√kg. Subgroup analysis indicated that the positive association between WWI and sNfL was significant across most subgroups, particularly in older populations. This study demonstrates a significant U-Shaped nonlinear association between WWI and sNfL levels. These findings provide new evidence linking abdominal obesity to neuronal health and offer critical insights for developing obesity-related intervention strategies aimed at mitigating neurodegenerative risks.