High prevalence of diabetes mellitus and metabolic syndrome in a South African coloured population: baseline data of a study in Bellville, Cape Town.

Objective: The coloured population has the second-highest prevalence of diabetes in South Africa. However, the data were based on a study conducted almost 20 years ago in a peri-urban coloured population of the Western Cape. We aimed to determine the prevalence of diabetes mellitus and metabolic syndrome in an urban coloured population in South Africa.

Design: In a cross-sectional survey, 642 participants aged ≥31 years were drawn from an urban community of Bellville South, Cape Town, from mid-January 2008 to March 2009. Type 2 diabetes was assessed according to the WHO criteria, and metabolic syndrome was based on the International Diabetes Federation (IDF), ATP III and 2009 Joint Interim Statement (JIS) definition.

Results: The crude prevalence of 28.2% (age-adjusted 26.3%, 95% confidence interval (CI) 22.0 - 30.3) for type 2 diabetes was: 4.4% (age-adjusted 3.2%, 95% CI 1.6 - 4.9) for impaired fasting glycaemia, and 15.3% (age-adjusted 15.0%, 95% CI 11.4 - 18.6) for impaired glucose tolerance. Undiagnosed type 2 diabetes was present in 18.1% (age-adjusted 16.8%, 95% CI 13.3 - 20.4). The crude prevalence of metabolic syndrome was higher with the JIS definition (62.0%) than the IDF (60.6%), and the National Cholesterol Education Program (NCEP) ATP III (55.4%). There was good overall agreement between the MetS criteria, k=0.89 (95% CI 0.85 - 0.92).

Conclusion: The prevalence of diabetes has increased hugely in the coloured community, and the high prevalence of undiagnosed diabetes portends that cardiovascular diseases might grow to epidemic proportions in the near future in South Africa.