Smoking Cessation Linked to Higher Short-Term Risk for Type 2 Diabetes
Although cigarette smoking increases the risk for type 2 diabetes, smoking cessation predicts higher short-term risk for the development of type 2 diabetes, according to the results of a prospective cohort study reported in the January 5, 2010, issue of the Annals of Internal Medicine.
“Cigarette smoking is an established predictor of incident type 2 diabetes mellitus, but the effects of smoking cessation on diabetes risk are unknown,” write Hsin-Chieh Yeh, PhD, from Johns Hopkins University in Baltimore, Maryland, and colleagues from the Atherosclerosis Risk in Communities (ARIC) Study.
The goal of this study was to test the hypothesis that smoking cessation would increase diabetes risk in the short term, possibly caused by weight gain related to quitting smoking. The study cohort consisted of 10,892 middle-aged adults free of diabetes at study enrollment from 1987 to 1989. Interview at baseline and at subsequent follow-up determined smoking status. Incident diabetes was identified by fasting glucose assays through 1998 and by self-report of physician diagnosis or use of diabetes medications through 2004.
Incident type 2 diabetes developed in 1254 adults during 9 years of follow-up. For adults in the highest tertile of pack-years vs those who never smoked, the adjusted hazard ratio (HR) of incident diabetes was 1.42 (95% confidence interval [CI], 1.20 – 1.67).
In the first 3 years of follow-up, 380 participants quit smoking. Compared with adults who never smoked, the HRs of incident diabetes among former smokers, new quitters, and continuing smokers were 1.22 (95% CI, 0.99 – 1.50), 1.73 (95% CI, 1.19 – 2.53), and 1.31 (95% CI, 1.04 – 1.65), respectively, after adjustment for age, race, sex, education, adiposity, physical activity, lipid levels, blood pressure, and ARIC Study center. These risks decreased dramatically after further adjustment for weight change and leukocyte count.
The highest risk for the development of type 2 diabetes occurred in the first 3 years after quitting (HR, 1.91; 95% CI, 1.19 – 3.05), but this risk gradually declined to 0 at 12 years.
“Cigarette smoking predicts incident type 2 diabetes, but smoking cessation leads to higher short-term risk,” the study authors write. “For smokers at risk for diabetes, smoking cessation should be coupled with strategies for diabetes prevention and early detection.”
Limitations of this study include observational design, precluding determination of causality; possible residual confounding, even with careful adjustment for known diabetes risk factors; lack of confirmation of diabetes self-report to classify persons as having diabetes; ascertainment of diabetes and smoking status based on telephone interviews for the supplementary analysis; and possible underrepresentation of smokers in later years of follow-up because of higher mortality or lower response rates.
“Despite the well-established association of cumulative smoking with long-term diabetes risk, smoking cessation does not seem to reduce the short-term risk for diabetes but rather increases it,” the study authors conclude. “Of course, smoking cessation has many beneficial health effects that outweigh this short-term risk….Our results imply that smoking prevention should be superior to smoking cessation as a means of reducing smoking-related risk for diabetes in the general population.”