Psoriasis and new-onset diabetes: a Danish nationwide cohort study

OBJECTIVE Psoriasis is associated with increased risk of cardiovascular events and increased prevalence of cardiovascular risk factors. Diabetes mellitus (DM) is a major contributor to cardiovascular morbidity and mortality that may be associated with psoriasis, but conflicting results have been presented and nationwide data on the risk of new-onset DM in patients with psoriasis have not been reported. RESEARCH DESIGN AND METHODS The study comprised a Danish population ≥10 years of age on 1 January 1997 who were followed until new-onset DM, death, or 31 December 2009. Information on comorbidity, concomitant medication, and socioeconomic status was linked on an individual level. The primary study end point was DM requiring pharmacotherapy. Incidence rates for the development of DM events per 1,000 observational years were calculated and adjusted. Incidence rate ratios (IRRs) were estimated by Poisson regression. RESULTS A total of 4,614,807 subjects were eligible for analysis, with a maximum follow-up of 13 years. In the study period, 52,613 patients with psoriasis, including 6,784 patients with severe psoriasis, were identified. The overall incidence rates for new-onset DM were 3.67 (CI 3.65-3.69), 6.93 (6.63-7.25), and 9.65 (8.68-10.73) for the reference population, mild psoriasis, and severe psoriasis, respectively. Compared with the reference population, the IRR of new-onset DM was increased in all patients with psoriasis, i.e., IRR 1.49 (CI 1.43-1.56) and 2.13 (1.91-2.37) for those with mild and severe psoriasis. CONCLUSIONS In this nationwide cohort, psoriasis was associated with increased incidence rates of new-onset DM. The association remained statistically significant after adjustment for confounding factors.