Leukocyte count, C-reactive protein level and incidence risk of type 2 diabetes among non-smoking adults: A longitudinal finding over 12 years from the Korean Genome and Epidemiology Study

Aims: Chronic low-grade inflammation is closely linked to the development and progression of type 2 diabetes mellitus (T2DM). Since inflammatory markers tend to be chronically elevated in current smokers, we examined the association of inflammatory markers, including leukocyte counts and C-reactive protein (CRP) levels, with incidence risk of T2DM in non-smoking adults. Methods: 5568 non-smoking participants aged 40–69 years without diabetes at baseline were selected from the Korean Genome and Epidemiology Study (KoGES), a large prospective cohort study. The hazard ratios (HRs) with 95% confidence intervals (CIs) for incident T2DM according to leukocyte and CRP quartiles, respectively, were calculated using multivariate Cox proportional hazards regression models. Results: During the 12-year follow-up period, T2DM developed in 1030 subjects (18.5%, 1030/5568), with an incidence rate of 3.1–4.9 per 2 years. The cumulative incidence of T2DM increased proportionally with increasing leukocyte and CRP quartiles. Compared with the reference first quartile, the HRs of incident T2DM in the second, third, and fourth quartiles of leukocyte counts and third and fourth quartiles of CRP levels increased in a dose-dependent manner after adjusting for potentially confounding variables. Conclusions: Leukocyte counts and CRP levels are predictors of incident T2DM independent of tobacco smoking.