Epidemiological aspects of diabetes in Cameroon: what is the role of tropical diabetes?

Diabetes is a worldwide public health problem made more acute in Africa by low socio-economic standards. Cases with an unusual clinical course are frequent and probably related to tropical diabetes, a syndrome that has not yet been precisely defined. This study reports the results of a prospective study carried out in Cameroon on 550 diabetic patients attending the Yaounde Central Hospital who were followed between December 1990 and July 1994. They were classified according to WHO criteria into 136 insulin-dependent diabetes mellitus (IDDM) (24.7%), 405 non-insulin- dependent diabetes mellitus (NIDDM) (73.7%) and 9 diabetes secondary to other diseases (1.6%). No cases of malnutrition-related diabetes mellitus (MRDM) were found, but 18 subjects were considered to have so-called "African diabetes". Investigation of the cohort showed epidemiological and clinical features markedly different from those of Caucasian diabetic subjects. The age of onset in IDDM occurred in all age groups, with a mean (+/- SD) close to that of NIDDM (40.9 +/- 4.8 years vs 49 +/- 10.9; P < 0.001). A clear male preponderance was found (M/F sex ratio = 1.63), as it has been reported in most studies from sub-Saharan Africa, in contrast with the slight female predominance noted in the Sahel and Saharan countries. An increased prevalence of young and non-obese NIDDM was also found. Seventy-nine NIDDM cases (19.5%) were detected in individuals under 40 years of age, including 31 with normal weight. Many atypical features were noted: IDDM in obese patients, NIDDM in ketotic subjects and patients with varying insulin requirements, all of which led to difficulties in classifying many diabetic patients according to current practices. All these uncommon features are concordant with the nature of tropical diabetes, including not only MRDM but also African diabetes which occurs in individuals older than MRDM patients who show no signs of malnutrition. Thus, tropical diabetes is apparently a syndrome with aetiological heterogeneity which requires further definition through clinical, genetic and immunological studies.