To assess and compare the prevalence of non-insulin-dependent diabetes mellitus (NIDDM) and impaired glucose tolerance (IGT) in two native Indian communities.
Two Algonquin communities in Quebec: River Desert and Lac Simon.
All native Indian residents aged at least 15 years were eligible; 621 (59%) of them volunteered to enroll in the study. The participation rate was 49% in River Desert and 76% in Lac Simon.
Fasting blood glucose level and serum glucose level 2 hours after 75-g oral glucose tolerance test, as described by the World Health Organization, in all subjects except those with confirmed diabetes. Other measures included body mass index (BMI), fat distribution and blood pressure.
The age-sex standardized prevalence rate of NIDDM was 19% in Lac Simon (95% confidence interval [CI] 16% to 21%); this was more than twice the rate of 9% in River Desert (95% CI 7% to 11%). The IGT rates were comparable in the two communities (River Desert 5%, Lac Simon 6%). NIDDM and IGT were uncommon under the age of 35 years. Only in Lac Simon was the NIDDM prevalence rate significantly higher among the women than among the men (23% v. 14%); almost half of the women aged 35 years or more had diabetes. In Lac Simon the rate of marked obesity (BMI greater than 30) was significantly higher among the women than among the men (37% v. 19%; p < 0.001); this sex-related difference was not found in River Desert (rates 31% and 23% respectively). Previously undiagnosed NIDDM accounted for 25% of all the cases. NIDDM and IGT were significantly associated with high BMI, sum of skinfold thicknesses and waist:hip circumference ratio (p < 0.001). The subscapular:triceps skinfold ratio, however, did not display such an association, nor did the age-adjusted systolic blood pressure.
The prevalence of NIDDM is high in Algonquin communities and may vary markedly between communities. Although widespread, particularly in women, obesity cannot entirely explain the much higher rate of NIDDM in Lac Simon. Family and lifestyle risk factors, in particular diet and activity patterns, are being analysed in the two communities.