Change from oral antidiabetic therapy to insulin and risk of urinary tract infections in Type 2 diabetic patients: a population-based prescription study

Abstract

Background Diabetes is a risk factor for urinary tract infections (UTI), but the impact of insulin treatment and glycaemic control on UTI risk is not clear. Methods We determined the risk of antibiotic-treated UTI episodes in a population-based cohort of 2737 Type 2 diabetic patients who switched from oral antidiabetic drug (OAD) to insulin therapy. Each patient was observed for 365 days before and after the switch date, excluding a 120-day time window around this date. Episodes of UTI were defined as filled prescriptions for a UTI-specific antibiotic. We used conditional logistic regression to estimate the relative risk (odds ratio) of having one or more UTIs in the insulin vs. OAD period overall and stratified by glycaemic change. Results After the switch to insulin, 53% of all patients experienced a decrease in individual mean hemoglobin A1c (median decrease=1.5%, interquartile range 0.9%-2.3%). Episodes of treated UTIs occurred in 446 (16.3%) Type 2 diabetic patients in the insulin period and 437 (16.0%) in the OAD period (relative risk 1.04, 95% CI 0.86–1.26). Stratified analyses showed no consistent association between levels of glycaemic improvement and decreased UTI risk during insulin treatment. Conclusions Among patients with Type 2 diabetes, no evidence was found that switch to insulin therapy with or without tightened glycaemic control decreased their high annual risk of antibiotic-treated UTI episodes.