Is Hyperinsulinaemia a Central Characteristic of a Chronic Cardiovascular Risk Factor Clustering Syndrome? Mixed Findings in Asian Indian, Creole and Chinese Mauritians

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Abstract
The aim of the study was to investigate whether the constellation of cardiovascular disease risk factors, described as Insulin Resistance Syndrome, exists in the multi‐ethnic population of Mauritius, and to assess whether hyperinsulinaemia is the key feature of this syndrome. A sample of 5080 Mauritian subjects (aged 25–74 years) was examined in a non‐communicable diseases survey in 1987. Survey procedure included an oral glucose tolerance test, and anthropometric, blood pressure, plasma lipids and serum insulin measurements. Abnormal glucose tolerance (diabetes and impaired glucose tolerance), general obesity, upper‐body obesity, hypertension, low HDL‐cholesterol, and hypertriglyceridaemia were defined as risk factor conditions. Mean values for a series of risk factor variables were compared between reference subjects (no risk factors) and those with a risk factor condition (either one condition only, or in combination with one or more others). Prevalence estimates for each risk factor condition in combination with three or more other conditions were three to four times greater than expected by chance, and levels of risk factors for subjects with more than one risk factor condition were further away from the reference levels than for those with just one condition. Fasting and 2‐h serum insulin levels were elevated for each condition when in combination with others, or to a lesser extent when isolated. However, this was not the case for isolated hypertension where insulin levels were not elevated. When adjusted for age, sex, and body mass index, insulin levels were only significantly elevated in subjects with upper‐body obesity if in association with general obesity. A clustering of cardiovascular risk factors was therefore found in Mauritius. However, insulin levels although high for most conditions were not high in hypertension.