INTRODUCTION: Secondhand smoke (SHS) exposure is a significant health risk, but current research often overlooks its broader impact on functional impairments in the general public. METHODS: This study utilized serum cotinine levels (SCL) from the 2013-2018 NHANES dataset to investigate physical disabilities associated with SHS exposure. SCL represents the combined concentration of cotinine and hydroxycotinine. The physical disabilities assessed include difficulties with hearing, vision, concentration, walking, dressing or bathing independently, and running errands alone. Logistic regression was applied to evaluate the relationship between SCL and physical disabilities in adults, with stratified analyses by age, gender, and race. A p<
0.05 was considered significant. RESULTS: Logistic regression analyses showed that SHS exposure was significantly associated with walking difficulty. Participants in the highest quartile of SCL (Q4) had significantly higher odds of walking difficulty compared to those in the lowest quartile (Q4 vs Q1, AOR=2.03
95% CI: 1.24-3.31, p-trend=0.010). Higher hydroxycotinine were associated with increased walking difficulty (AOR=1.48
95% CI: 1.06-2.08, p=0.030). Individuals in the highest quartile of hydroxycotinine (Q4) faced more difficulty running errands (AOR=2.09
95% CI: 1.13-3.88, p-trend=0.036). Among males, the highest quartiles of cotinine and hydroxycotinine were more strongly associated with walking difficulty than in females (cotinine: AOR=2.92 vs 1.49
hydroxycotinine: AOR=3.23 vs 1.78). In adults aged ≥60 years, higher SCL, cotinine, and hydroxycotinine levels were significantly associated with walking difficulty (SCL, AOR=1.58
95% CI: 1.24-2.02)
cotinine, AOR=1.80
95% CI: 1.21-2.67
hydroxycotinine, AOR=4.57
95% CI: 1.92-10.89). An 'L'-shaped association was observed for ln(hydroxycotinine) and walking difficulty, with a significant association beyond -1.306 (AOR=2.57
95% CI: 1.33-4.96, p=0.005). CONCLUSIONS: Higher SHS is significantly associated with various physical disabilities, especially in men and older adults.