Examining the health impacts of climate change through electronic health records: A rapid review

Introduction: Temperature extremes, including elevated heat and cold, are important environmental determinants of health, the frequency and duration of which are increasing due to climate change. Ecological and time-series studies have established links with adverse outcomes but often lacked individual-level detail. Electronic health records (EHR) provide an alternative source, yet their use in climate-health research remains inconsistent. Aim: First, to undertake a methodological examination of how the health impacts of temperature extremes are captured and coded in EHR-based studies across healthcare settings and to describe the current methods and coding practices in the existing evidence base; and second, to synthesize evidence on the health outcomes associated with extreme temperature events to identify gaps in the current literature to inform future research. Methods: We conducted a rapid review of studies using EHR data to examine associations between temperature extremes and health outcomes across healthcare settings. The aim was to assess how health impacts of temperature extremes have been captured and coded within EHR-based research, and to identify methodological and coding-related gaps. Searches of seven databases identified eligible studies, and data were extracted on exposure definitions, outcome coding, methods, findings, and limitations, using key terms for climate change exposure and health outcomes from EHRs. The findings and limitations were narratively summarized and tabulated to highlight trends, methodological issues, and evidence gaps. Results: Of the 1,616 studies identified, 526 duplicates were removed, leaving 1,090 for screening; 58 studies met our inclusion criteria. Extreme heat was most frequently studied, with fewer analyses of extreme cold. Common outcomes included morbidity, cardiovascular admissions, asthma, and pregnancy-related conditions. Mental health outcomes were rarely assessed, subgroup analyses were mostly age-based, and studies focused on high-income countries. Exposure metrics and coding practices varied widely, with limited reporting of diagnostic codes and individual-level mediators. Conclusion: Harmonized exposure definitions, broader outcome coverage, and integration of socio-demographic and individual-level factors are needed to strengthen EHR-based climate-health research and guide targeted interventions.