Seasonal patterns of all-cause and cause-specific mortality in Antananarivo, Madagascar, 1976-2011

Deaths are not randomly distributed in the course of the year; they often exhibit distinct seasonal variations. In the northern hemisphere, seasonal patterns are mostly characterized by a summer trough and a winter peak in adult mortality, predominantly due to respiratory, cerebrovascular, and ischemic heart diseases. There has been little research conducted on seasonal mortality in developing countries because of the lack of adequate data. Tacking advantage of a long series of death records registered in the urban setting of Antananarivo since 1976, we examine seasonal patterns of all-cause and cause-specific mortality. We show that the seasonality of mortality is much more marked in young children and the elderly than in adults of working age. Child mortality is higher during the rainy season because of infectious and parasitic diseases, as well as nutritional deficiencies. By contrast, the elderly die more during the cold months of July and August, mainly because of diseases of the circulatory and respiratory systems. The seasonality of child deaths has significantly reduced over the last thirty years whereas it has not changed for people aged 60 and over.