Ethnic differences in the relationships between obesity and glucose-metabolic abnormalities: a cross-sectional population-based study.

Abstract

To evaluate whether body mass index (BMI) and other anthropometric indices of visceral obesity vary by ethnic group in their distribution and their relationship to metabolic abnormalities. Cross-sectional study. Canadian men and women, aged 35-75 years, of South Asian (n=342), Chinese (n=317), European (n=326) and Aboriginal (n=301) descent were recruited using stratified random sampling. Anthropometric indices (BMI, waist to hip ratio (WHR) and waist circumference (WC)), metabolic markers (fasting glucose, HbA1c, the ratio of total cholesterol/HDL) and clinical markers (systolic blood pressure) were assessed. In subjects with BMI<30 kg/m2, the mean marker levels in people with elevated WC (>88 cm in women, >102 cm in men) vs people with normal WC were 6.16 vs 5.34 mmol/l for fasting glucose, 6.05 vs 5.66% for HbA1c and 5.46 vs 4.68 for the ratio of total cholesterol to HDL (P<0.001 in each case). At nearly every given level of BMI, non-European ethnic groups displayed significantly higher marker levels than Europeans. For example, for a given BMI, age and sex, the difference between European and non-European groups in HbA1c levels was 0.53% (95% confidence interval (CI): 0.37-0.69) for South Asians, 0.37% (95% CI: 0.2-0.54) for Chinese and 0.95% (95% CI: 0.78-1.12) for Aboriginal People. Uniform cut-points for the classification of obesity using BMI, WHR or WC result in marked variation in the levels of glucose-metabolic abnormalities between ethnic groups. Existing action thresholds for these anthropometric indices do not apply to non-European ethnic groups and warrant revision.