The Prevalence of Diabetes in the Kingdom of Tonga

Abstract

OBJECTIVE—To determine the prevalence of diabetes, impaired glucose metabolism, and related risk factors in Tonga.

RESEARCH DESIGN AND METHODS—A randomly selected representative national sample of 1,024 people aged >15 years was surveyed. Each participant had fasting blood glucose and HbA_1c measured. Subjects with a fasting blood glucose >5.0 mmol/l (90 mg/dl) and <11.1 mmol/l (200 mg/dl) or a fasting blood glucose ≤5.0 mmol/l and an HbA_1c >6.0% and every fifth subject with a fasting blood glucose ≤5.0 mmol/l and a normal HbA_1c had a 75-g oral glucose tolerance test (OGTT). A total of 472 individuals had an OGTT based on these criteria. Subjects with a fasting blood glucose ≥11.1 mmol/l and an elevated HbA_1c were diagnosed as having diabetes.

RESULTS—The mean age was 41.3 years, and the mean BMI was 32.3 kg/m². The age-standardized prevalence of diabetes was 15.1% (CI 12.5–17.6), 12.2% (8.7–15.8) in men and 17.6% (14.0–21.1) in women (NS), of which only 2.1% was previously diagnosed. A total of 75% of people with newly diagnosed diabetes had a fasting plasma glucose ≥7.0 mmol/l (126 mg/dl). The prevalence of impaired glucose tolerance was 9.4% (7.3–11.5) and of impaired fasting glycemia 1.6% (0.7–2.6). Undiagnosed diabetes was significantly associated with increasing age, obesity, hypertension, and a family history of diabetes.

CONCLUSIONS—The current prevalence of diabetes in Tonga is 15.1%, of which 80% is undiagnosed. A similar survey in 1973 reported a 7.5% diabetes prevalence, indicating a doubling of diabetes over the past 25 years. In addition, lesser degrees of glucose intolerance are common, and much of the community is overweight