More Diabetes in African American Heavy Smokers

● African Americans who smoke more than 1 pack of cigarettes per day have a higher incidence of diabetes mellitus.
● High numbers of cigarettes smoked per day as well as higher total pack years of smoking are associated with impaired pancreatic beta cell function.

Cigarette smoking is a well-known cause of disease and mortality impacting multiple organ systems, in particular the respiratory and cardiovascular systems. Conflicting evidence exists as to whether smoking effects insulin resistance and the incidence of diabetes mellitus.

Wendy B. White, MD, PhD, deputy director, Jackson Heart Study Undergraduate Training and Education Center, Tougaloo College, in Tougaloo Mississippi and fellow researchers point out that racial/ethnic disparities in smoking behaviors have been described, including longer smoking durations for blacks vs whites and lower cessation rates in blacks vs both whites and Hispanics. But little is known about the effect of smoking on African American patients with regards to diabetes mellitus. Further, the mechanisms that might lead smoking to predispose patients to develop diabetes mellitus are not clear.

The authors sought to explain the relationship between smoking intensity and dose on incident diabetes mellitus in the African American community. They report their findings in a recent Journal of the American Heart Association article.

The Study

The Jackson Heart Study was a prospective cohort study looking at 5301 African American patients in Mississippi over 4 years. Smoking data were compared to incidence of diabetes mellitus; 2991 participants were included in the final results.

The Results

●  No difference was found between unadjusted fasting glucose levels (P=0.71), or hemoglobin A1c values (P=0.67) when smoking was considered.
●  Plasma insulin levels were lower in subjects who smoked more than 20 cigarettes per day (P<.001).
●  Body mass index and waist circumference were significantly lower in high-intensity smokers (P<.001 and P+0.006 respectively).
●  Diabetes incidence rates were 15%, 20%, and 17% in never smokers, past smokers and current smokers respectively.
●  Following adjustment, smoking status was not associated with risk of diabetes mellitus.
●  Smoking intensity was associated with higher incidence of diabetes mellitus when compared to never smokers (P=0.01).
●  Pack years were also associated with higher incidence of diabetes mellitus (P=0.02).
●  Smoking status and intensity did not affect insulin resistance, however pack years (dose) did increase pancreatic beta cell insulin resistance.

Implications for Physicians

● Smoking cessation should be encouraged in all patients.
● Patients at high risk for diabetes such as African Americans with other independent risk factors should be targeted aggressively for smoking cessation.

Source: White WB, Cain LR, Benjamin EJ, et al. High-intensity cigarette smoking is associated with incident diabetes mellitus in black adults: The Jackson Heart Study. J Am Heart Assoc. 2018;7:e007413; originally published January 12, 2018; doi: 10.1161/JAHA.117.007413