Incidence of Type 2 diabetes in the elderly German population and the effect of clinical and lifestyle risk factors: KORA S4/F4 cohort study

Aims To determine the incidence of Type 2 diabetes in an elderly population in Germany and its association with clinical and lifestyle factors. Methods Oral glucose tolerance tests (OGTT, World Health Organization criteria) were carried out in a random sample of 1353 subjects (age group 55-74 years; 62% response) in Augsburg (Southern Germany) (1999-2001). The cohort was re-investigated in 2006-2008. Of those individuals without diabetes (baseline), 887 (74%) participated in the follow-up. Results Ninety-three (10.5%) developed diabetes during the 7-year follow-up period {standardized incidence rates [95% confidence interval (CI)] per 1000 person-years: total 15.5; 12.6, 19.1; men 20.2; 15.6, 26.1; women 11.3; 7.9, 16.1}. In both sexes, those who developed diabetes were slightly older, were more obese, had a more adverse metabolic profile (higher glucose values, HbA(1c), fasting insulin, uric acid, and triglycerides) and were more likely to have hypertension at baseline than were participants remaining free of diabetes (P < 0.05). On stepwise logistic regression, age, parental diabetes, body mass index, uric acid, current smoking, HbA(1c) and fasting and 2-h glucose (OGTT) were strong predictors of diabetes incidence. The risk of diabetes was higher in subjects with isolated impaired glucose tolerance (odds ratio 8.8; 95% CI 5.0, 15.6) than in isolated impaired fasting glucose (4.7; 2.2, 10.0), although the difference did not reach statistical significance. Conclusions For the first time, we have estimated the incidence of Type 2 diabetes in an elderly German cohort and demonstrated that it is among the highest in Europe. The OGTT appears to be useful in identifying individuals with high Type 2 diabetes risk. Our results support a role of smoking in the progression to diabetes.