Short-Term Effects of Ambient Temperature on Acute Heart Failure Decompensation: Phenotype-Specific Risk in a Time-Stratified Case-Crossover Study

BACKGROUND: Acute decompensated heart failure (ADHF) exhibits seasonal variations, yet the short-term effects of ambient temperature, independent of seasonality, remain poorly studied. Moreover, temperature-sensitive exacerbation phenotypes are not well defined, limiting the development of effective preventive strategies. We aimed to investigate the effects of ambient temperature on ADHF admissions and clinical presentation profiles. METHODS: We included 26 874 patients with ADHF who had been registered in the Tokyo Coronary Care Unit Network Database between January 2014 and December 2019. The onset date of ADHF leading to hospitalization, along with clinical characteristics such as age, left ventricular function, cause of ADHF, and hemodynamic profile, was assessed by cardiologists at each participating center. Climate data were obtained from an observatory near the admitting hospital. We used a time-stratified case-crossover design with distributed lag nonlinear models to explore the association between ambient temperature and ADHF admissions over lag days 0 to 5, with stratified analyses by the clinical presentations. RESULTS: Exposure to extremely low temperatures (-4.5 °C [first percentile]) increased the risk of ADHF (1.80, 95% CI, 1.40-2.31) when referenced to the temperature of lowest risk (29.0 °C [99th percentile]). The excess risk of lower temperature appeared immediately on the day of exposure (lag 0). This risk was larger in patients aged ≥70 years and otherwise consistent across subgroups. Notably, the temperature-risk relationship differed by hemodynamic profiles; risk for ADHF with hypertension rose at low temperatures, whereas ADHF with low blood pressure showed the opposite pattern, with risk increasing at high temperatures (odds ratio, 6.25 [95% CI, 1.07-36.6] at the 99th percentile). CONCLUSIONS: Low ambient temperature increased ADHF risk, especially in older adults, while temperature effects differed by hemodynamic phenotype. Incorporating temperature exposure into risk assessment may enable targeted prevention of climate-related decompensation. REGISTRATION: URL: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000015310; Unique identifier: UMIN000013128.