Extreme Temperatures and Stroke Mortality: Evidence From a Multi-Country Analysis

• DOI: 10.1161/strokeaha.123.045751
• Publication Date: 2024-05-22T16:11:22Z
• Authors: Barrak Alahmad; Haitham Khraishah; Meghana Kamineni; Dominic Royé; Stefania I. Papat...; Ana Maria Vicedo-...; Yuming Guo; Eric Lavigne; Ben Armstrong; Francesco Sera; Aaron S. Bernstein; Antonella Zanobetti; Eric Garshick; Joel Schwartz; Michelle L. Bell; Fahd Al-Mulla; Petros Koutrakis; Antonio Gasparrini; Achilleos Souzana; Fiorella Acquaotta; Shih-Chun Pan; Micheline Sousa Z...; Valentina Colistro; Tran Ngoc Dang; Do Van Dung; Francesca K. De’ ...; Alireza Entezari; Yue-Liang Leon Guo; Masahiro Hashizume; Yasushi Honda; Ene Indermitte; Carmen Íñiguez; Jouni J.K. Jaakkola; Ho Kim; Whanhee Lee; Shanshan Li; Joana Madureira; Fatemeh Mayvaneh; Hans Orru; Ala Overcenco; Martina S. Ragettli; Niilo R.I. Ryti; Paulo Hilario Nas...; Noah Scovronick; Xerxes Seposo; Susana Pereira Silva; Massimo Stafoggia; Aurelio Tobias
• Keywords: Male; Take urgent action to combat climate change and its impacts; Extreme temperatures; Cross-Over Studies; Hot Temperature; Extreme Heat; Middle Aged; Stroke; Make cities and human settlements inclusive, safe, resilient and sustainable; Hemorrhagic Stroke; climate change; extreme cold; hemorrhagic stroke; ischemic stroke; temperature; Humans; Female; Mortality; Ensure healthy lives and promote well-being for all at all ages; Aged; Ischemic Stroke

BACKGROUND: Extreme temperatures contribute significantly to global mortality. While previous studies on temperature and stroke-specific outcomes presented conflicting results, these studies were predominantly limited to single-city or single-country analyses. Their findings are difficult to synthesize due to variations in methodologies and exposure definitions.

METHODS: Within the Multi-Country Multi-City Network, we built a new mortality database for ischemic and hemorrhagic stroke. Applying a unified analysis protocol, we conducted a multinational case-crossover study on the relationship between extreme temperatures and stroke. In the first stage, we fitted a conditional quasi-Poisson regression for daily mortality counts with distributed lag nonlinear models for temperature exposure separately for each city. In the second stage, the cumulative risk from each city was pooled using mixed-effect meta-analyses, accounting for clustering of cities with similar features. We compared temperature-stroke associations across country-level gross domestic product per capita. We computed excess deaths in each city that are attributable to the 2.5% hottest and coldest of days based on each city’s temperature distribution.

RESULTS:

We collected data for a total of 3 443 969 ischemic strokes and 2 454 267 hemorrhagic stroke deaths from 522 cities in 25 countries. For every 1000 ischemic stroke deaths, we found that extreme cold and hot days contributed 9.1 (95% empirical CI, 8.6–9.4) and 2.2 (95% empirical CI, 1.9–2.4) excess deaths, respectively. For every 1000 hemorrhagic stroke deaths, extreme cold and hot days contributed 11.2 (95% empirical CI, 10.9–11.4) and 0.7 (95% empirical CI, 0.5–0.8) excess deaths, respectively. We found that countries with low gross domestic product per capita were at higher risk of heat-related hemorrhagic stroke mortality than countries with high gross domestic product per capita ( P =0.02).

CONCLUSIONS: Both extreme cold and hot temperatures are associated with an increased risk of dying from ischemic and hemorrhagic strokes. As climate change continues to exacerbate these extreme temperatures, interventional strategies are needed to mitigate impacts on stroke mortality, particularly in low-income countries.