Food Insecurity Predicts Serum Cotinine in US Adults Who Use Tobacco Products: Evidence from NHANES 2015–2018 Combined Data

Background: Tobacco use and food insecurity frequently co-occur and may influence each other bidirectionally. While most prior research has focused on tobacco use as a driver of food insecurity, studies typically rely on self-reported tobacco measures. This study examined associations between food insecurity and serum cotinine, a biomarker of nicotine exposure, and evaluated potential mediating and moderating factors. Methods: Data from the 2015–2018 National Health and Nutrition Examination Survey (NHANES) were analyzed for 2,149 adult tobacco users. Cotinine concentrations were log-transformed and modeled using generalized linear models, adjusted for sociodemographic covariates, depression, and body mass index. Mediation was tested with causal mediation analysis and structural equation modeling, and moderation with interaction terms. Results: Each unit increase in food insecurity severity was associated with an approximately 10% increase in cotinine concentrations after adjustment for covariates (p = 0.018). Depression neither mediated nor moderated the food insecurity-cotinine association. Income-to-poverty ratio significantly moderated the relationship (p=0.009): the positive food insecurity-cotinine slope grew stronger as income rose, whereas at or below the poverty line food insecurity was not significantly associated with cotinine. In smoker subsample analyses, food insecurity also moderated the smoking frequency-cotinine slope, with the most food-insecure participants showing the shallowest dose-response relationships.Conclusions: Food insecurity is associated with elevated cotinine concentrations, but effects depend on household economic resources and on how smoking behavior translates into nicotine uptake. Stabilizing food security may be critical for reducing tobacco-related health disparities.