Abstract Rationale Extreme heat events are becoming more frequent, prolonged, and intense due to anthropogenic climate change, with disproportionate health impacts among older adults. Although prior studies link high temperatures to increased mortality, the strength and consistency of associations with respiratory morbidity remain less well characterized. Objectives To systematically review and quantitatively synthesize evidence on the association between extreme heat and respiratory morbidity and mortality among elderly populations worldwide. Methods We searched peer-reviewed studies (2000-2025) examining extreme heat and respiratory outcomes in individuals aged ≥60 years, including acute care encounters (e.g., emergency department visits or ambulance attendances), hospital admissions, and mortality. Eligible studies used time-series, case-crossover, or other population-based designs and reported relative risks (RRs) with 95%CIs. Heat exposure was defined by absolute thresholds, percentile-based cutoffs, diurnal temperature range (DTR), or multi-day heatwave criteria. Pooled RRs were estimated using DerSimonian-Laird random-effects meta-analysis. Measurements and Main Results Extreme heat exposure was associated with significantly increased respiratory morbidity and mortality among older adults. The pooled morbidity RR for acute care encounters increased 11% (RR = 1.11, 95%CI: 1.04-1.19) and for hospital admissions increased 6% (RR = 1.06, 95%CI: 1.04-1.08). Respiratory mortality increased 18% (RR = 1.18, 95%CI: 1.07-1.29). Associations remained robust in sensitivity analyses and were consistent across continents, exposure metrics, and outcome definitions, with risk magnitudes comparable to or exceeding those linked to ambient particulate matter. Conclusions Extreme heat poses a substantial and growing respiratory health threat to aging populations, underscoring the need for targeted adaptation and mitigation strategies. This abstract is funded by: This study was funded by NIH: NIEHS grants P20-ES034490 (ALM and GDL), and R01-ES034490 (GDL). Alexandra Purcell was funded by the Internal Medicine Scholars Training for Academic Research (IMSTAR) and the Pulmonary Medical Student Scholars Program.
Purcell et al. (Fri,) studied this question.