Glycaemic control, disease duration and beta-cell function in patients with Type 2 diabetes in a Swedish community. Skaraborg Hypertension and Diabetes Project.

AIMS To examine determinants for glycaemic control in primary care patients with Type 2 diabetes. METHODS In a community-based surveillance of primary care patients with Type 2 diabetes, 190 men and 186 women were consecutively identified and examined for cardiovascular risk factors. Insulin resistance and beta-cell function were estimated using homeostasis model assessment (HOMA). Good glycaemic control was defined as HbA(1c) < 6.5%. RESULTS Following adjustment for age and gender, HbA(1c) > or = 6.5% was associated with duration of diabetes (10.6 vs. 6.4 years, P < 0.001), lower levels of serum insulin (6.3 vs. 8.0 mU/l, P = 0.012), higher serum triglyceride levels (2.0 vs. 1.7 mmol/l, P = 0.002) and impairment of beta-cell function (HOMA index 19.5 vs. 45.8, P < 0.001). The association between HbA(1c) levels and duration remained with adjustment for age, gender, waist-hip ratio (WHR) and serum triglycerides (odds ratio (OR) for HbA(1c) > or = 6.5% by 5 years diabetes duration = 1.7; 95% confidence interval (CI) 1.4--2.1) but was lost following additional adjustment for beta-cell function (OR for HbA(1c) > or = 6.5% = 1.3; 95% CI 0.96-1.7). In a separate linear regression with beta-cell function as the dependent variable there was a significant association with HbA1c after adjustments for differences in age, gender, WHR, serum triglyceride levels and diabetes duration (P < 0.001). CONCLUSIONS Increasing HbA1c by time was associated with declining beta-cell function.