Do early onset and pack-years of smoking increase risk of type II diabetes?

Background: Type II diabetes is not only major public health problem but also heavy fiscal burden to each nation's health care system around the world. This study aimed to investigate the effect of early onset and pack-years of smoking on type II diabetes risk.

Methods: We used the most recent cross-sectional National Health and Nutrition Examination Survey set of South Korea (2010) and the United States (2009-2010). Participants who were diagnosed with diabetes after age 20 were included (South Korea: n = 7273, 44% male; U.S.: n = 3271, 52% male). Cox proportional models, stratified by sex and country, were used to estimate hazard ratios.

Results: 7.1% of South Korean men, 5.5% of South Korean women, 15.5% of U.S. men, and 12.4% of U.S. women had type II diabetes; 40% of South Korean men, 34% of U.S. men, and 21% of U.S. women began smoking before age 20 (57%, 49%, 36% of those who had type II diabetes, respectively). Type II diabetic participants were older and married; have a higher BMI, low income, and less education; lack moderate physical activity, smoked more and earlier compared to those without type II diabetes. Differences in risk factors including life-style behaviors and SES were found in both diabetic and non-diabetic populations. Men who began smoking before age 16 had a higher type II diabetes risk than who never smoked (South Korea: hazard ratio [HR] 2.46, 95% confidence interval [CI] 1.04-5.79; U.S.: HR 1.64, 95% CI 1.01-2.67), as did U.S. men who began smoking between 16 and 20 years (HR 1.58, 95% CI 1.05-2.37). Smoking pack-years were also associated with type II diabetes in U.S. men (HR 1.07, 95% CI 1.01-1.12). In women population, however, associations were not found.

Conclusions: Early onset of smoking increases type II diabetic risk among men in South Korea and the U.S., and type II diabetic risk increases with higher pack-years in U.S. men, however, no associations were found in women population. Underage tobacco policy and education programs are strongly needed in both countries.