Seasonal variation in mortality in Scotland

Background Seasonal patterns in mortality have been recognized for many yea rs. This study assesses seasonal variation in mortality in Scotland between 1981 and 1993 and considers its association with socioeconomic status and outdoor temperature. Methods Lagged Poisson regression analysis of numbers of deaths and average weekly temperature with adjustment for serial autocorrelation and influenz a epidemics. Results There was significant seasonal variation in weekly death rates with a difference of about 30% between a summer trough and a winter peak. This variation was principally attributable to respiratory disease, cerebrovascu lar disease and coronary artery disease. Seasonal variation in mortality fe ll from around 38% in 1981-1983 to around 26% in 1991-1993. There was no cl ear evidence of a relationship between socioeconomic status and seasonal mo rtality, however the extent of the fall in seasonal variation was greater i n deprived areas than in affluent areas. Overall, a 1 degrees C decrease in mean temperature was associated with a 1% increase in deaths one week late r. The lag in this relationship varied by cause of death and underlying tem perature. Conclusions Seasonal variations in mortality and the relationship between t emperature and mortality are a significant public health problem in Scotlan d. It is likely that the strength of this relationship is a result of the p opulation being unable to protect themselves adequately from the effects of temperature rather than the effects of temperature itself.