MORTALITY SEASONALITY IN ESCAZU, COSTA-RICA, 1851-1921

Mortality seasonality has been frequently reported in populations livi ng under various ecological conditions. The number of deaths apparentl y varies by month as a result of fluctuating climatic variables. Here, I examine whether mortality was seasonally distributed in Escazu, Cos ta Rica, from 1851 to 1921. I also investigate which cause of death ma de the greatest contribution to mortality periodicity and which climat ic variable caused the seasonality of deaths. Two different methodolog ical approaches are used: chisquare and Freedman tests to determine th e presence of seasonality and Box-Jenkins time series analysis. The te sts to determine the presence of seasonality show that mortality was s trongly seasonal in Escazu, with the highest number of deaths occurrin g during the early months of the rainy season. The Box-Jenkins analysi s successfully modeled the series from 1851 to 1891 with a seasonal pa rameter. However, the more recent years of the data were modeled witho ut seasonal parameters. Thus the time series approach indicates that m ortality became less seasonally distributed in more recent years. An a nalysis of gastrointestinal- and respiratory-related deaths showed tha t gastrointestinal causes had a strong seasonal distribution (with mor e deaths in the early months of the rainy season) and that respiratory causes did not. Therefore rainfall appears to have been responsible f or mortality seasonality through its impact on the frequency of gastro intestinal maladies. The analysis of cause of death also shows that th e seasonal fluctuation of gastrointestinal-related deaths decreased in the more recent years. Such a decrease is reflected in the nonseasona l Box-Jenkins model for the 1892-1921 years.