Objective: To determine the current prevalence of impaired glucose tolerance (IGT) and non-insulin-dependent diabetes mellitus (NIDDM) in Melanesians of three coastal Papua New Guinean communities, to relate this to previous studies, and to investigate plasma glucose distributions in these populations.
Design: Cross-sectional survey, using 75 g oral glucose tolerance tests and World Health Organization criteria.
Setting: Rural Papuan villages of Wanigela and Kalo, and Wanigela people of the urban squatter settlement of Koki, Port Moresby.
Subjects: All adults aged 25 years or more living in the three communities were eligible, with response rates of 77.2% (Koki), 88.1% (Wanigela) and 72.5% (Kalo).
Main outcome measures: Prevalence of abnormal glucose tolerance, risk factor levels, fasting and two-hour plasma glucose concentration.
Results: Age-standardised prevalence of NIDDM in Koki Wanigelas was 27.5% in men and 33.0% in women; an additional 20.5% of men and 22.0% of women had IGT. Even in the youngest age group (25-34 years), 36.5% of subjects had abnormal glucose tolerance. The overall prevalences of NIDDM and IGT in rural Wanigelas were 11.7% and 17.0% respectively. In Kalo both were uncommon. The prevalences of IGT and NIDDM in Koki had doubled over a 14-year period. The age-standardised prevalence of abnormal glucose tolerance in the Koki Wanigelas is the second highest in the world after the Arizona Pima Indians, and higher than in Micronesian Nauruans, even though the latter are more obese. Both fasting and two-hour glucose concentrations in all age groups in Koki were clearly bimodal, a mixture of two log-normal distributions.
Conclusions: The Wanigela people of Papua New Guinea have an extra-ordinary susceptibility to glucose intolerance which is exposed after adoption of modern lifestyle habits. A "founder effect" may explain the high frequency of a diabetogenic genotype in this population.