Obesity and the use of insulin: a study of patients with type 2 diabetes in the UK

Objective: This analysis examines how obesity affects the prescribing of insulin for individuals with type 2 diabetes and poor glycemic control. Methods: Data were obtained from the UK General Practice Research Database for the years 2000-2004. Patients were eligible if they had been identified as having type 2 diabetes and had undergone at least two valid glycosylated hemoglobin (HbA(1c)) tests. Additionally, patients had to have poor glycemic control on the index date (HbA(1c)>7.4), no use of insulin 6 months prior to the index date, and at least 30 months of data after the index date (N=6468). Descriptive statistics were used to examine unadjusted differences between obese and nonobese patients. A Cox proportional hazards model was applied to examine the relationship between obesity and the relative likelihood of initiation of insulin while controlling for differences in patient characteristics, medication use, and RbA(1c) levels. Results: Obese individuals were significantly younger (P<.01), significantly more likely to be treated with two oral antidiabetic agents (P=.02), and significantly less likely to be treated with oral monotherapy (P=.02). Controlling for a wide range of factors that may impact receipt of insulin, results revealed that obese individuals had a "hazard' of initiation of insulin significantly lower than that of nonobese patients (hazard ratio=0.814, P=.01). Conclusions: Patient age, severity of illness, and prior medication use all affect whether the individual will be initially prescribed insulin. Moreover, the results of this study demonstrate that obesity is an additional critical factor in physicians' decision to begin treatment with insulin. (C) 2008 Elsevier Inc. All rights reserved.