Rising diabetes prevalence among urban-dwelling black South Africans

Abstract

Objective: To examine the prevalence of and the association of psychosocial risk factors with diabetes in 25-74-year-old black Africans in Cape Town in 2008/09 and to compare the prevalence with a 1990 study.

Research design and methods: A randomly selected cross-sectional sample had oral glucose tolerance tests. The prevalence of diabetes (1998 WHO criteria), other cardiovascular risk factors and psychosocial measures, including sense of coherence (SOC), locus of control and adverse life events, were determined. The comparison of diabetes prevalence between this and a 1990 study used the 1985 WHO diabetes criteria.

Results: There were 1099 participants, 392 men and 707 women (response rate 86%). The age-standardised (SEGI) prevalence of diabetes was 13.1% (95% confidence interval (CI) 11.0-15.1), impaired glucose tolerance (IGT) 11.2% (9.2-13.1) and impaired fasting glycaemia 1.2% (0.6-1.9). Diabetes prevalence peaked in 65-74-year-olds (38.6%). Among diabetic participants, 57.9% were known and 38.6% treated. Using 1985 WHO criteria, age-standardised diabetes prevalence was higher by 53% in 2008/09 (12.2% (10.2-14.2)) compared to 1990 (8.0% (5.8-10.3)) and IGT by 67% (2008/09: 11.7% (9.8-13.7); 1990: 7.0% (4.9-9.1)). In women, older age (OR: 1.05, 95%CI: 1.03-1.08, p<0.001), diabetes family history (OR: 3.13, 95%CI: 1.92-5.12, p<0.001), higher BMI (OR: 1.44, 95%CI: 1.20-1.82, p = 0.001), better quality housing (OR: 2.08, 95%CI: 1.01-3.04, p = 0.047) and a lower SOC score (≤ 40) was positively associated with diabetes (OR: 2.57, 95%CI: 1.37-4.80, p = 0.003). Diabetes was not associated with the other psychosocial measures in women or with any psychosocial measure in men. Only older age (OR: 1.05, 95%CI: 1.02-1.08, p = 0.002) and higher BMI (OR: 1.10, 95%CI: 1.04-1.18, p = 0.003) were significantly associated with diabetes in men.

Conclusions: The current high prevalence of diabetes in urban-dwelling South Africans, and the likelihood of further rises given the high rates of IGT and obesity, is concerning. Multi-facetted diabetes prevention strategies are essential to address this burden.

Figure 1. Prevalence of glycaemic categories based on 1998 WHO criteria presented by age categories.

Footnote: IFG: impaired fasting glycaemia; IGT: impaired glucose tolerance.

Figure 2. Diabetes prevalence based on 1985 WHO criteria presented by age categories for men and women in 1990 and 2008/09.

Footnote: *1990: 65+ years, 2008/09: 65–74 years.