Seasonal incidence of diabetes mellitus in tropical Africa.

During a 6-year period from 01 June 1981 to 30 May 1987, 1250 newly diagnosed African diabetic patients were registered at Muhimbili Medical Centre, Dar es Salaam, Tanzania. A seasonal pattern in the presentation of patients for both insulin-requiring and non-insulin-requiring diabetic patients was observed (p less than 0.001). The peak months of presentation were August through to November, with the greatest number of patients presenting in September (170 patients in 6 years) and the smallest number in June (55 patients). Similar patterns were found for month of onset of symptoms, with the peak month August (180 patients) and the trough month May (56 patients) (p less than 0.001). A similar pattern of presentation was observed in Morogoro, a town in another region of Tanzania. Seasonality in the presentation of insulin-requiring and non-insulin-requiring diabetes may therefore occur in tropical as well as temperate climates.