Quitting Smoking For 8 Years Linked To Fewer Diabetes Eye And Kidney Complications

Researchers analyzed national health insurance data from 209,698 adults with type 2 diabetes in Korea (average age 57.2, 61% female), following them from a final health checkup between 2009 and 2013 through the end of 2023. People were sorted into never smokers (162,861), quitters who stayed smoke-free across at least four repeated checkups (11,848), and continuous smokers (34,989).

Compared with people who kept smoking, those who had quit for 8 or more years had a 19% lower risk of any diabetic microvascular complication (adjusted hazard ratio 0.81), a 21% lower risk of diabetic kidney disease (0.79), a 41% lower risk of diabetic eye disease (0.59), and a 20% lower risk of diabetic nerve damage (0.80). Quitting for 6 to 7 years was linked to a 24% lower risk of nerve damage (0.76), but quitting for under 2 years was linked to a 12% higher risk of kidney disease (1.12). The incidence rate of any complication was 301.9 per 10,000 person-years among continuous smokers versus 237.6 per 10,000 person-years among those quit 8 or more years.

Smoking is known to damage small blood vessels throughout the body by driving inflammation and impairing the endothelium, the inner lining of blood vessels; this general mechanism is the background link between smoking and nerve, eye, and kidney damage in diabetes. The lower risk in this study reached statistical significance only among men; the female-only analysis was limited by a small number of events.