Predictors of insulin initiation in Metformin and sulfonylurea users in primary care practices: The role of kidney function

Abstract

Aims: The aims were to investigate predictors of insulin initiation in new users of metformin or sulfonylureas in primary care practices, in particular, its association with decreased renal function. Methods: Data from 9103 new metformin and 1120 sulfonylurea users with normal baseline glomerular filtration rate (EGFR) >90 ml/min/1.73 m2 from 1072 practices were retrospectively analyzed (Disease Analyzer Germany: 01/2003-06/2012). Cox regression models and propensity score matching was used to adjust for confounders (age, sex, practice characteristics, comorbidity). Results: Insulin treatment was started in 394 (4.3%) metformin and in 162 (14.5%) sulfonylurea users within 6 years (P < .001). Kaplan-Meier curves (propensity score matched patients) showed that the metformin group was at a lower risk of insulin initiation compared to sulfonylurea users throughout the study period. A substantial EGFR decline (category: 15-<30 ml/min/1.73 m2) was significantly associated with a higher likelihood to have insulin initiated (adjusted hazard ratio [HR]: 2.39; 95% CI: 1.09-5.23) in metformin but not in sulfonylurea (HR: 0.45; 95% CI: 0.16-1.30) users. Conclusions: New users of sulfonylurea monotherapy in primary care practices in Germany were about 3-fold more likely to start insulin therapy than those with metformin. Kidney function decline was associated with earlier insulin initiation in metformin but not in sulfonylurea users.