Relationships between diabetes duration, metabolic control and beta-cell function in a representative population of type 2 diabetic patients in Sweden.

To clarify whether metabolic control and beta-cell function deteriorate with increasing duration of diabetes, we investigated in a cross-sectional study Type 2 diabetic patients in an area-based population. Type 2 diabetic patients (n = 231: 112 males, 119 females) were identified by age at onset > or = 35 years, fasting levels of C-peptide > 0.04 nmol l-1, and absence of islet cell antibodies. Body weight was slightly elevated (BMI 26.8 +/- 0.3 kg m-2), however 76/210 (36%), had normal weight (BMI < 25 kg m-2). Fasting blood glucose rose significantly during the first 10 years of known diabetes from 8.2 +/- 0.3 mmol l-1 in patients with 0-5 years of duration to 9.9 +/- 0.7 mmol l-1 in those with 5-10 years of duration, p < 0.01 and HbA1c from 6.4 +/- 0.2 to 7.4 +/- 0.4%, p < 0.05. Fasting C-peptide levels decreased after 10 years duration from 0.90 +/- 0.06 nmol l-1 during 5-10 to 0.69 +/- 0.08 nmol l-1 during 10-15 years of diabetes, p < 0.05. The proportion of insulin treated patients increased from 13% (12/94) with 0-5 years of duration to 33% (13/39) with 10-15 years and 60% (18/30) with more than 15 years of duration. In conclusion in Type 2 diabetic patients without signs of autoimmunity, metabolic control, and beta-cell function deteriorate with increasing duration of diabetes, leading to common but not inevitable occurrence of 'secondary failure'.