Abstract
Background:
Stroke is a leading cause of morbidity and mortality worldwide, with rising incidence and healthcare burden. Climate change–related environmental stressors, particularly thermal discomfort from heat and cold extremes, may influence stroke risk, though findings remain inconsistent and mechanisms vary by subtype. This study evaluates associations between temperature variability and stroke risk across subtypes and U.S. climate regions.
Methods:
We analyzed nationwide U.S. Veterans Affairs (VA) data (2010–2014), identifying stroke encounters using ICD-9 codes and classifying them into hemorrhagic, intracranial (ICAD), extracranial (ECAD), and acute cerebrovascular disease (ACVD). A case-crossover design matched cases to control periods within 5±2 months prior. Exposures included ambient temperature, thermal discomfort (deviation from monthly norms), and thermal shock (hourly variability). Conditional logistic regression modeled associations across eight climate regions.
Results:
Among 354,742 encounters, stroke incidence peaked in August and was lowest in February, with regional variation. Stroke risk increased under both extreme heat and cold: 46% higher at 3 SD below and 76% higher at >3 SD above monthly norms. Each 10°C increase in lagged temperature was associated with a 9.4% higher stroke risk (OR 1.009, p<0.01), and temperature variability increased risk by 1.9% (OR 1.019, p<0.01). Heat stress was associated with ECAD and ICAD, while cold stress was linked to ACVD. Hemorrhagic stroke showed no significant association. Older individuals were at greater risk.
Conclusions:
Thermal extremes and variability increase stroke risk in subtype- and region-specific patterns, supporting targeted, climate-informed prevention strategies.