Quantifying the risk of infectious diseases for people with diabetes.

OBJECTIVE In vitro evidence shows that immune function is compromised in people with diabetes. Although certain rare infections are more common and infection-related mortality is higher, the risk of acquiring an infectious disease for diabetic patients has never been quantified. RESEARCH DESIGN AND METHODS A retrospective cohort study using administrative data compared all people with diabetes in Ontario, Canada, on 1 April 1999 to matched nondiabetic people (n = 513,749 in each group). The risk ratios of having an infectious disease and of death attributable to infectious disease between those with and without diabetes were calculated. Secondary analysis individually examined common infectious diseases. The study was repeated using a second pair of cohorts defined in 1996 to confirm stability of the estimates. RESULTS Nearly half of all people with diabetes had at least one hospitalization or physician claim for an infectious disease in each cohort year. The risk ratio for diabetic versus nondiabetic people was 1.21 (99% CI 1.20-1.22) in both cohort years. The risk ratio for infectious disease-related hospitalization was up to 2.17 (99% CI 2.10-2.23). The risk ratio for death attributable to infection was up to 1.92 (1.79-2.05). Many individual infections were more common in people with diabetes, especially serious bacterial infections. CONCLUSIONS Diabetes confers an increased risk of developing and dying from an infectious disease, corroborating both in vitro evidence and commonly held clinical belief. In addition to microvascular and macrovascular sequelae, clinicians should consider infection a complication of diabetes.