Aim: To determine the prevalence of insulin resistance, impaired fasting glycaemia, impaired glucose tolerance, and diabetes mellitus in a rural Maori community, and to compare different methods for identifying individuals with insulin resistance.
Methods: 589 randomly selected individuals from the Ngati Porou Hauora Register aged 25 years and over and resident on New Zealand's East Coast north of Gisborne were invited to participate in the study. A questionnaire was administered, anthropometric measures made, and blood samples taken for an oral glucose tolerance test and biochemical analysis. Impaired fasting glycaemia, impaired glucose tolerance, and diabetes mellitus were defined according to World Health Organization (WHO) diagnostic criteria, and among those persons with normal glucose tolerance, insulin resistance was calculated according to the McAuley formula and three other recognised methods for calculating insulin sensitivity.
Results: The overall age-standardised prevalence of diabetes (both known and newly diagnosed) was 10.6% and the age-standardised prevalence of insulin resistance was 37.0%. Age-specific diabetes rates were high among the older age groups, peaking at 34.1% for 60-69 year olds, whereas age-specific insulin resistance rates were high among the young age groups with the highest rate (44.3%) occurring among 30-39 year olds. Persons identifying as insulin-resistant reported higher rates of gout and family history of diabetes--and were found to have a higher waist circumference, blood pressure, and lower high-density lipoprotein (HDL) cholesterol than those without a glucose metabolism disorder.
Conclusion: Diabetes is a common disorder among this population, but insulin resistance is even more prevalent, especially among young age groups. This is considerable cause for concern given that insulin resistance is believed to be the underlying cause of most cases of type 2 diabetes mellitus, and is confirmed by these data to be associated with a high degree of cardiovascular risk.