Unusual summer and winter temperatures between 2000 and 2008 were associated with an increased rate of death in Americans over 65, living in New England, USA, a paper published online in Nature Climate Change shows. The research suggests that swings in temperature during the seasons can have a comparable impact on mortality rates to particularly hot summer seasons or cold winter seasons.
Joel Schwartz and colleagues studied data from the US national health insurance programme, Medicare, which includes information on the age, race and sex of all individuals as well as their date of death. They cross-referenced 2,740,308 residents with local average temperature and temperature variability data for different postal (ZIP) codes to estimate the impact of changing temperatures on mortality.
The researchers found that although living in warmer ZIP codes was associated with reduced mortality in both summer and winter, living in ZIP codes with more variable in-season weather increased mortality rates. They speculate that living in areas with more variable temperatures made exercise and other behavioural changes more difficult, which may have contributed to increasing mortality rates.
The research suggests that climate change may affect mortality rates by making seasonal weather more unpredictable, creating temperature conditions significantly different to those to which people have become acclimatized.