A studyof the association of cold weather and all-cause and cause-specific mortality on the island of Ireland between 1984 and 2007.

Abstract

Background: This study explored the differences between the seasonal mortality rates (by age and gender) between the two jurisdictions (the Republic of Ireland (RoI) and Northern Ireland (NI)). The study assessed the relationship between cold temperatures and daily mortality, and assessed for effect modification of the cold weather-mortality relationship by age and gender. Methods: Mortality rates were calculated for each cause-specific mortality group during various seasons in both jurisdictions. A time-stratified case-crossover approach was applied to examine the cold weather-mortality relationship, 1984-2007. The daily mortality risk was explored in association with exposure to daily maximum temperatures on the same day and up to 6 weeks preceding death, during the winter months and extended cold period (October-March), using distributed lag models. Model stratification by age and gender assessed for modification of the cold weather-mortality relationship. Results: The winter mortality rates were significantly greater than the summer rates. NI experienced higher mortality from cardiovascular disease, respiratory disease and stroke. The impact of cold weather in the winter months persisted up to 35 days in the RoI, with a cumulative mortality increase for all-cause of 6.4% (95%CI: 4.8%-7.9%) with regards to every 1oC drop in the daily maximum temperature with similar associations for cardiovascular disease and stroke with twice as much for respiratory diseases. The associations were less pronounced and less persistent in NI. Conclusions: The study observed excess winter mortality. The cold weather-mortality associations increased with age with some suggestion of gender differences. There were strong cold weather-mortality associations in both jurisdictions, with suggestive differences in associations by age and gender. The findings suggest the potential contribution of societal differences, and require further exploration. These findings will hopefully contribute to the current efforts to modify fuel policy and reduce winter mortality in both jurisdictions