Inhaled corticosteroids and the risks of diabetes onset and progression.

BACKGROUND Systemic corticosteroids are known to increase diabetes risk, but the effects of high-dose inhaled corticosteroids are unknown. We assessed whether the use and dose of inhaled corticosteroids increase the risk of diabetes onset and progression. METHODS We formed a new-user cohort of patients treated for respiratory disease during 1990-2005, identified using the Quebec health insurance databases and followed through 2007 or until diabetes onset. The subcohort treated with oral hypoglycemics was followed until diabetes progression. A nested case-control analysis was used to estimate the rate ratios of diabetes onset and progression associated with current inhaled corticosteroid use, adjusted for age, sex, respiratory disease severity, and co-morbidity. RESULTS The cohort included 388,584 patients, of whom 30,167 had diabetes onset during 5.5 years of follow-up (incidence rate 14.2/1000/year), and 2099 subsequently progressed from oral hypoglycemic treatment to insulin (incidence rate 19.8/1000/year). Current use of inhaled corticosteroids was associated with a 34% increase in the rate of diabetes (rate ratio [RR] 1.34; 95% confidence interval [CI], 1.29-1.39) and in the rate of diabetes progression (RR 1.34; 95% CI, 1.17-1.53). The risk increases were greatest with the highest inhaled corticosteroid doses, equivalent to fluticasone 1000 μg per day or more (RR 1.64; 95% CI, 1.52-1.76 and RR 1.54; 95% CI, 1.18-2.02; respectively). CONCLUSIONS In patients with respiratory disease, inhaled corticosteroid use is associated with modest increases in the risks of diabetes onset and diabetes progression. The risks are more pronounced at the higher doses currently prescribed in the treatment of chronic obstructive pulmonary disease.