Nocturnal warming and emergency department admissions: a nationwide association and projection study in Singapore

Climate change is increasingly influencing the prevalence and severity of various diseases. While previous studies have linked climate variables to emergency department (ED) admissions, few have examined cause-specific patterns, particularly in tropical urban settings. We quantified exposure–response relationships between minimum temperature (T-min) and cause-specific ED admissions in Singapore and projected future admission rates and excess incidence ratios (EIRs) from 2021 to 2060 under three Shared Socioeconomic Pathway (SSP) climate scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5). We also compared admissions during extreme warm-night events with those under normal temperature conditions. We analyzed weekly cause-specific ED admissions across nine disease categories from 2010 to 2018, linked to daily minimum temperature and precipitation. Generalized additive models with negative binomial distributions were used to estimate lagged associations (up to six weeks) between weekly mean T-min and ED admission rates, with population as an offset. EIRs were derived to characterize temperature–admission relationships, compare historical and future periods, and estimate excess admissions attributable to warm nights. Model performance was evaluated using temporal hold-out validation, and uncertainty was quantified via simulation-based uncertainty propagation. Distinct nonlinear temperature–disease relationships were observed. Cardiovascular, endocrine, genitourinary, infectious/parasitic, musculoskeletal, and skin diseases exhibited higher incidence rates when T-min exceeded ~ 25.1 °C, while chronic respiratory diseases responded only above 25.9 °C. Oral diseases increased at cooler temperatures. Projections indicated significant increases in ED admissions across most categories under future scenarios, especially under SSP585. Elevated nighttime temperatures substantially increase cause-specific ED admissions in tropical Singapore, and continued warming is projected to exacerbate healthcare demand. Elevated nighttime temperatures are associated with increased emergency department admissions across multiple disease categories in Singapore. There is an urgent need for both mitigation and adaptation strategies–such as urban cooling, improved housing design, and early-warning systems–to reduce health risks in a warming climate.