Current but Not Former Smoking Is Associated With Higher HbA1c in Adults Without Diabetes

AimWe examined associations between smoking and HbA1c among U.S. adults, and whether these associations vary by diabetes status. MethodsWe analyzed NHANES data from 2015-2018 for adults aged [&ge;]20 years. Smoking was assessed by self-report and serum cotinine. Survey-weighted multivariable linear regression was used to evaluate the association between smoking and HbA1c in the full population (N=9,214) and in adults without diabetes (N=7,328), adjusting for demographics, blood pressure, waist circumference, lipids, and C-reactive protein. ResultsAfter adjustment for cardiometabolic covariates, there was no significant association between smoking and HbA1c in the full population (former: {beta}=0.029%, p=0.30; current: {beta}=0.053%, p=0.13). Among adults without diabetes, former smoking was not associated with HbA1c, whereas current smoking remained significantly associated (former: {beta}=-0.001%, p=0.923; current: {beta}=0.067%, p<0.001). These findings were similar when cotinine was used as the exposure measure, with active smoking ([&ge;]3.0 ng/mL) associated with higher HbA1c among non-diabetic adults (p<0.001), but not in the full population. ConclusionsAmong adults without diabetes, current but not former smoking was associated with higher HbA1c. The absence of an association in former smokers suggests that this effect may attenuate following cessation. These findings support early cessation interventions and may inform cessation counseling and diabetes screening.