Development of a heat mortality surveillance approach for England

Abstract Background England’s unprecedented temperatures in 2022 and 2023 highlighted the severe risks of rising global temperatures on public health. This study considers the impact of heatwave events on mortality rates, supporting the development of improved health surveillance and intervention strategies. Methods Firstly, heat-associated mortality for each heat episode was estimated by comparing observed daily mortality values with the expected baseline of daily deaths. Secondly, the historic temperature-mortality relationship was established at national and regional levels using a distributed lag non-linear model with temperature and mortality data from the previous 5 years. Finally, modelled estimates of heat-associated excess mortality were generated based on the historic temperature-mortality relationships, to assess any difference between observed and modelled estimates. Results In 2022 which saw record-breaking maximum temperatures in the UK, an estimated 2,985 (2,258-3,712) heat-associated deaths were recorded across five heat episodes, the highest annual count to date. Despite relatively cool temperatures, 2023 saw the third-highest heat-associated mortality since reporting began in 2016 of 2,295 (1,681-2,910). Comparisons between modelled and observed mortality were generally similar, but showed statistically significant discrepancies for certain heat episodes across the two summers. Conclusions Heatwaves have a rapid and clear impact on health, emphasising the need for effective early warning systems and interventions. The comparison of observed mortality with predictions from historic temperature-mortality relationships at regional level demonstrates the need for a nuanced approach to surveillance and health protection for adverse heat, with factors other than temperature also playing a critical role in health impacts. This will inform continuous improvements in England’s impact-based Heat Health Alerting system. Key messages • Heatwaves pose a significant risk to public health, as evidenced by the unprecedented excess deaths during the record-breaking temperatures in England in Summer 2022. • Comparison of observed mortality with predictions from historic data can provide insight into contextual factors modulating the health impacts of heat, and inform future surveillance and response.