Age-Associated Increase in Abdominal Obesity and Insulin Resistance, and Usefulness of AHA/NHLBI Definition of Metabolic Syndrome for Predicting Cardiovascular Disease in Japanese Elderly with Type 2 Diabetes Mellitus

BACKGROUND: Management of metabolic syndrome (MetS) seems to constitute an efficient strategy to attain successful ageing. Although the clinical entity of MetS in patients with diabetes mellitus has been discussed, there is very little information on MetS-type cardiometabolic risk factor clustering in diabetic elderly. OBJECTIVE: To determine the relationship among age-associated changes in obesity, insulin resistance, and clustering of MetS-type risk factors, in association with vascular complications, in Japanese elderly with type 2 diabetes. METHODS: A cross-sectional study was conducted of 812 diabetic elderly enrolled in the Japanese Elderly Diabetes Intervention Trial. Information on diabetes, blood examinations and complications was obtained. Abdominal obesity, insulin resistance and prevalence of MetS risk factor clustering, defined by three sets of criteria from the International Diabetes Federation (IDF), the Japanese Society of Internal Medicine (JSIM), and the American Heart Association and the National Heart, Lung, and Blood Institute (AHA/NHLBI), were analyzed. RESULTS: Waist circumference and insulin resistance estimated by homeostasis model assessment insulin resistance (HOMA-IR) increased with age, followed by a partial decrease at age 80 and over. Prevalence of IDF-MetS and JSIM-MetS also increased with age at least until the age of 80, whereas the incidence of AHA/NHLBI-MetS did not show any apparent age changes. There was a significant crude linear association between waist circumference and HOMA-IR, which was highly elevated in IDF and AHA/NHLBI overlapping with MetS, and also elevated in AHA/NHLBI without abdominal obesity. Although IDF-MetS and JSIM-MetS, which specify abdominal obesity, did not always appear to be associated with cardiovascular diseases, AHA/NHLBI-MetS, comprising both abdominal obesity and non-abdominal obesity, independently correlated with coronary heart disease and stroke after adjustment for other risk factors of atherosclerotic diseases. CONCLUSION: There was an age-associated increase in the prevalence of abdominal obesity and insulin resistance in elderly diabetic Japanese subjects, with a clear relationship between waist circumference and insulin resistance. However, insulin resistance was elevated not only in cases with but also in those without abdominal obesity if accompanied by clustering of metabolic disorders. The AHA/NHLBI definition of MetS proved to be the most useful to predict cardiovascular disease in the diabetic elderly.