Intra-urban differences in the prevalence of the metabolic syndrome in southern India -- the Chennai Urban Population Study (CUPS No. 4).

Abstract

To assess the influence of socioeconomic status on the prevalence of the metabolic syndrome in an urban south Indian population in Chennai. The Chennai Urban Population Study is an epidemiological study involving two residential colonies in Chennai (formerly Madras) in south India representing the middle and lower income groups. All individuals > or = 20 years of age living in the colonies were invited to participate in the study. Of the total 1399 eligible subjects, 1262 individuals (479 belonging the middle income group colony and 783 from the low income group colony) participated in the study. The overall response rate was 90.2%. The main outcome measures were the prevalence rates of the various components of the metabolic syndrome. There were significant differences in the socioeconomic status and lifestyle of the inhabitants of the two areas. The mean monthly income of the Tirumangalam (middle income) group (Rs8075 +/- 3859) was significantly higher than the T. Nagar (low income) group (Rs1399 +/- 916). The dietary profile of the middle income group showed higher intake of calories, fat and sugar compared to low income group (P < 0.001). The age-standardized prevalence rates of the various components of the metabolic syndrome were significantly higher in the middle compared to the low income group - diabetes (12.4 vs. 6.5%), impaired glucose tolerance (7.5 vs. 2.9%), hypertension (14.9 vs. 8.4%), obesity (males 38 vs. 13.4%, females 33.1 vs. 24.2%), hypercholesterolaemia (24.2 vs. 14.2%) and hyperinsulinaemia (16.7 vs. 6.6%) P < 0.001). Although the prevalence of coronary artery disease and hypertriglyceridaemia were higher in the middle income group, the differences did not reach statistical significance. The relative odds ratio for diabetes and impaired glucose tolerance increased significantly with increase in income while hypercholesterolaemia, hypertriglyceridaemia, hypertension and coronary artery disease showed no significant changes. Logistic regression analysis revealed that geographical area (higher social class) had a strong association with the components of the metabolic syndrome even after inclusion of other risk factors like age and body mass index in the model. Significant differences exist in the prevalence of various components of the metabolic syndrome even within an urban environment and this appears to be influenced by socioeconomic status.