Interaction Between Smoking and Olfactory Function on Frailty: A Population-Based Cross-Sectional Study.

Background and Aims: Frailty is a multidimensional syndrome characterized by decreased physiological reserves and is closely associated with aging-related adverse outcomes. Although smoking and olfactory dysfunction are individually associated with frailty, their potential interactions have not been thoroughly investigated. Methods: We used data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014, which included 5192 participants. Smoking status and self-reported olfactory function were assessed using standardized questionnaires. Frailty was defined using a 36-item Frailty Index (FI), with FI > 0.2 indicating frailty. Multivariate logistic regression models were used to examine the independent and joint associations of smoking and olfactory function with frailty, after adjusting for demographic and lifestyle covariates. Interaction and stratified analyses were also performed. Results: Current smoking status and altered olfactory function were independently associated with an increased risk of frailty. In fully adjusted models, nonsmokers had a lower odds of frailty compared with smokers (odds ratio [OR] = 0.41, 95% confidence interval [CI]: 0.29-0.58), and participants with normal olfactory function had a lower odds of frailty than those with altered olfactory function (OR = 0.57, 95% CI: 0.48-0.69). A significant interaction was observed between smoking and olfactory function (P interaction = 0.001). The highest odds of frailty were found in participants who smoked and had altered olfactory function (OR = 2.49, 95% CI: 1.88-3.31). Conclusion: Our findings revealed a synergistic association between smoking, altered olfactory function, and frailty risk. This interaction in relation to the healthcare of older people highlights the importance of sensory screening and behavioral risk assessment in the early identification of frailty, especially in smokers.