Objective: To investigate methods for the detection of different clusterings of the insulin-resistant abnormalities consistent with the concept of the 'metabolic syndrome' in clinical practice, and to research the occurrence of these clusters in a middle-aged Finnish population.
Methods: We studied a random sample of 207 middle-aged subjects in the city of Tampere, and all 1148 subjects of four middle-aged age groups in Pieksamaki town, in central Finland. Clusterings of the following eight markers of insulin resistance were recorded as the main outcome measures: 1) at least one first-degree relative with non-insulin-dependent diabetes (NIDDM); 2) obesity: body mass index (BMI) > or = 30 kg/m2; 3) central adiposity: waist-to-hip ratio (WHR) > or = 1.00 in men and > or = 0.88 in women; 4) hypertension: systolic blood pressure > or = 160 mmHg or diastolic blood pressure > or = 95 mmHg, or receiving drug treatment for hypertension; 5) hypertriglyceridaemia > or = 1.70 mmol/l; 6) low high-density lipoprotein (HDL) cholesterol: < 1.0 mmol/l in men and < 1.20 mmol/l in women; 7) abnormal glucose metabolism according to WHO criteria and 8) hyperinsulinaemia: fasting plasma insulin > or = 13.0 mU/l.
Results: The metabolic syndrome, defined as a clustering of dyslipidaemia (hypertriglyceridaemia, low HDL cholesterol, or both) and insulin resistance (abnormal glucose tolerance, hyperinsulinaemia, or both) was present in 17% of men and in 8% of women; this sex difference was statistically significant (P< .001). The syndrome was detectable with a sensitivity of 96% and a specificity of 55% by the combined four markers of insulin resistance (NIDDM in a close relative, obesity, central adiposity and hypertension).
Conclusion: In clinical practice, the metabolic syndrome can be detected during normal clinical examination. The occurrence of the syndrome is already high by middle age.