The relationship between insulin resistance and cardiovascular risk factors in overweight/obese non-diabetic Asian adults: the 1992 Singapore National Health Survey

OBJECTIVE: Insulin resistance (IR) is associated with cardiovascular risk factors including hypertension, dyslipidemia, glucose intolerance and hyperuricemia. The relationship between IR and these cardiovascular risk factors in obese non-diabetic individuals is not well studied. We explore this relationship by comparing the cardiovascular risk factors among insulin-sensitive and insulin-resistant overweight/obese non-diabetic Asian adults in the 1992 National Health Survey of Singapore. DESIGN AND MEASUREMENTS: A total of 3568 subjects were examined in the survey, which involved a combination of disproportionate stratified sampling and systematic sampling. Anthropometric measurements, level of physical activity, blood pressure, insulin, lipid profile, uric acid and standard 75 g oral glucose tolerance test were performed after a 10 h overnight fast. Subjects with diabetes were excluded from the analysis. Homeostasis model assessment (HOMA) was used to assess insulin sensitivity. Relative LDL size was derived from the formula LDL/ApoB. We defined insulin-sensitive individuals as having a HOMA value <1.479 (below median in individuals without diabetes; n = 3226) and overweight/obesity as body mass index (BMI) greater than or equal to 25.0 kg/m(2). RESULTS: There were 156 insulin-sensitive (S) and 679 insulin-resistant (R) overweight/obese individuals, respectively. The groups did not differ in terms of gender and ethnic distribution and level of physical activity. However, subjects in group S were younger than those in group R (mean +/- s.d.; 40.1 +/- 12.1 vs 42.4 +/- 12.7 y; P < 0.05). Group R individuals were also slightly more obese globally and centrally than group S (BMI = 28.2 +/- 3.2 vs 27.1 +/- 2.8 kg/m(2); waist circumference (WC) = 86.7 +/- 9.3 vs 82.5 +/- 8.3 cm; P < 0.01). There were more subjects with impaired glucose tolerance (IGT) in group R than in group S (29.7 vs 16.0%; P < 0.01). After adjustment for age and indices of global and regional obesity (ie BMI and WC), insulin-resistant individuals showed higher apolipoprotein B, triglyceride, fasting (FPG) and 2 h post-load plasma glucose (2hPG) but lower HDL and LDL size. Further adjustment for FPG, 2hPG and level of physical activity had minimal impact on the results. CONCLUSIONS: Insulin-resistant overweight/obese non-diabetic Asian adults had greater burden of the cardiovascular dysmetabolic syndrome than insulin-sensitive overweight/obese individuals. This could not be fully explained by differences in global and regional obesity, glucose tolerance and level of physical activty.