To examine the independent and combined relationship of race/ethnicity and cotinine-based smoking status in relation to poor glycemic control in US adults with T2DM in a sex-stratified analysis.

We abstracted data from the 1999 to 2018 NHANES examination. We defined poor glycemic control as glycated hemoglobin A1C ≥ 8% (if aged ≥ 75 years) or A1C≥ 7% (aged 20–65 years). Participants were nonpregnant individuals aged ≥ 20 years with known diabetes. Race/ethnicity was self-reported and categorized as non-Hispanic white (NHW), non-Hispanic black (NHB) and Hispanic. We used generalized linear models to estimate prevalence ratio of poor glycemic control, after adjusting for confounders.

We included 7,537 adults with T2DM. The overall prevalence of poor glycemic control was 44.9%. Among nonsmokers, the risk of poor glycemic control increased by 14% (P=.06) in NHB and 30% (P<.0001) in Hispanic, compared with their relatives in NHW group. When compared with NHW not exposed to tobacco smoking, the risk of poor glycemic control was significantly higher in Hispanic men, independent of smoking status. The prevalence ratio was 1.31 (95% CI: 1.10–1.57) in nonsmokers and 1.32 (95% CI: 1.00–1.74) in smokers. In women not exposed to tobacco smoke, the prevalence ratio was significantly higher in both NHB [1.29 (95% CI: 1.04–1.58)] and Hispanic [1.33 (95% CI: 1.08–1.63)].

Overall, tobacco smoking did not appear to confer additional risk for poor glycemic control beyond that of race/ethnicity.