Health effects of milder winters: a review of evidence from the United Kingdom

Shakoor Hajat

Cold-related mortality and morbidity remains an important public health problem in the UK and elsewhere. Health burdens have often reported to be higher in the UK compared to other countries with colder climates, however such assessments are usually based on comparison of excess winter mortality indices, which are subject to biases. Daily time-series regression or case-crossover studies provide the best evidence of the acute effects of cold exposure. Such studies report a 6% increase in all-cause deaths in England & Wales for every 1 °C fall in daily mean temperature within the top 5% of the coldest days. In major Scottish cities, a 1 °C reduction in mean temperature below 11 °C was associated with an increase in mortality of 2.9%, 3.4%, 4.8% and 1.7% from all-causes, cardiovascular, respiratory, and non-cardio-respiratory causes respectively. In Northern Ireland, a 1 °C fall during winter months led to reductions of 4.5%, 3.9% and 11.2% for all-cause, cardiovascular and respiratory deaths respectively among adults. Raised risks are also observed with morbidity outcomes. Hip fractures among the elderly are only weakly associated with snow and ice conditions in the UK, with the majority of cases occurring indoors. A person's susceptibility to cold weather is affected by both individual- and contextual-level risk factors. Variations in the distributions of health, demographic, socio-economic and built-environment characteristics are likely to explain most differences in cold risk observed between UK regions. Although cold-related health impacts reduced throughout much of the previous century in UK populations, there is little evidence on the contribution that milder winters due to climate change may have made to reductions in more recent decades. Intervention measures designed to minimise cold exposure and reduce fuel poverty will likely play a key role in determining current and future health burdens associated with cold weather.