Social determinants of heat-related mortality in England: a time-stratified case-crossover study using primary care records.

Background: Despite increases in heat-related deaths in England, there has been limited progress in developing interventions in primary care that identify and target individuals at risk. Lack of understanding of individual-level socioenvironmental risk factors limits development of an evidence-based approach to targeted prevention. Objective: To identify individual-level non-clinical risk factors for heat-related mortality in England using primary care records and to assess the potential of these socio-environmental factors as effect modifiers for the association between ambient temperature and death. Methods: A time-stratified case-crossover analysis was undertaken of nine potential risk factors at the individual level and categorised into risk factor subgroups. 430 682 patients with valid records were included in the study population, obtained from the Clinical Practice Research Datalink. Conditional logistic regression was used to characterise associations between temperature and the risk of death on hot days and to investigate the modifying effect of each risk factor. Results: Older ages, females, ethnic minorities and those living in the most deprived areas all had increased risk of death during periods of heat. An increasing trend in ORs was observed with increasing amounts of alcohol intake and increasing body mass index, excluding the obese-3 group. No differences in risks were observed by marital status or frailty category. Conclusions: This is the first study in England to assess the role of socioenvironmental factors in modifying heat risk at an individual level. The results provide important evidence on the role of disadvantage in driving the inequitable distribution of climate change impacts, and the need for better socioeconomic data linked to health records. For clinical practice, the findings highlight the importance of incorporating an assessment of individual socioenvironmental circumstances when prioritising patients at highest risk during heat events.