Prevalence and Risk Factors
From 1993-1995, 728 members of the Sandy Lake community aged 10-79 years were screened for diabetes using World Health Organization diagnostic criteria. The results were as follows:
Diabetes Impaired Glucose Tolerance (IGT)
(*adjusted using the 1991 Canadian population)
(reference: Harris SB, Gittelsohn J, Hanley AJG, Barnie A, Wolever TMS, Gao XJ, Logan A, Zinman B. The prevalence of NIDDM and associated risk factors in Native Canadians. Diabetes Care 1997;20:185-187)
When results for the sub-group aged 30-65 years were examined separately and adjusted to the world-standard population, Sandy Lake was found to have the 3rd highest prevalence of diabetes in the world.
A number of factors that are associated with increased risk of diabetes in Sandy Lake have been identified:
Obesity: Individuals who were overweight were at very high risk of developing diabetes. Those who had excess fat around their mid-sections (abdominal obesity) were at particularly high risk.
(reference: Harris SB, Gittelsohn J, Hanley AJG, Barnie A, Wolever TMS, Gao XJ, Logan A, Zinman B. The prevalence of NIDDM and associated risk factors in Native Canadians. Diabetes Care 1997;20:185-187)
Diet: Diabetes was associated with low consumption of dietary fibre and vegetables, and with a high intake of dietary fat.
(references: (i) Wolever TMS, Hamad S, Gittelsohn J, Gao XJ, Hanley ALG, Harris SB, Zinman B.. Low dietary fibre and high protein intakes associated with newly diagnosed diabetes in a remote aboriginal community. Am J Clin Nutr 1997;66:1470-4.
(ii) Gittelsohn J, Wolever TMS, Harris SB, Harris-Giraldo R, Hanley AJG, Zinman B. Specific patterns of food consumption and preparation are associated with diabetes and obesity in a Native Canadian Community. Journal of Nutrition 1998;128:541-547)Physical Activity: Low levels of physical activity and poor physical fitness were associated with a number of conditions closely related to diabetes, including obesity and elevated insulin levels.
(references: (i) Hanley AJG, Harris SB, Gao XJ, Kwan J, Zinman B.. Serum immunoreactive-leptin concentrations in a Canadian aboriginal population with high rates of non-insulin-dependant diabetes mellitus Diabetes Care 1997;20:1408-15. (ii) Hanley AJG, Harris SB, Gittelsohn J, Wolever TMS, Saksvig B, Zinman B. Overweight among children and adolescents in a Native Canadian community: prevalence and associated factors. Am J Clin Nutr 2000;71:693-700).
Inherited Factors: Individuals who have inherited a variant of the HNF-1a gene were found to be at high risk for diabetes. This genetic risk factor appears to be unique to the Sandy Lake community. We are currently attempting to discover the way in which this gene increases a person’s likelihood of developing diabetes.
(reference: Hegele RA, Cao H, Harris SB, Hanley AJG, Zinman B.. The hepatic nuclear factor-1a G319S variant is associated with early onset type 2 diabetes in Canadian Oji-Cree. J Clin Endocrinol Metab 1999;84:1077-82.)
People with diabetes are at very high risk of developing a number of complications, including heart disease, blindness, kidney failure, and amputations. We are currently developing a strategy to document to prevalence of complications in Sandy Lake, and to implement a screening programme to detect the early signs of complications (which will allow for more effective prevention and treatment).
The frequency of hospitalizations for heart disease among Sandy Lake residents has increased substantially over the past 15 years. It is likely that this is due to the large increase in diabetes prevalence over past 20-30 years. Results from the prevalence survey showed that community members with diabetes have substantially higher levels of blood lipids (fats) compared to those without diabetes.
(source: Harris SB, Hanley AJG, Gittelsohn J, Hegele R, Connelley P, Zinman B. The impact of type 2 diabetes mellitus on cardiovascular risk factors and ischaemic heart disease in an isolated Canadian Native population. (manuscript under review))