Introduction: As global temperatures rise, extreme heat events are becoming increasingly prevalent in urban areas. While links between colder weather and increased rates of aneurysmal subarachnoid hemorrhage (aSAH) are well documented, the effects of extreme heat on aSAH have yet to be evaluated as such. This study investigates rupture rates in 13,397 intracranial aneurysm (IA) patients at Barrow Neurological Institute in Phoenix, Arizona where temperatures frequently exceed 90°F.
Methods: Retrospective data from January 2016 to December 2023 was analyzed for patients with intracranial aneurysms at Barrow. Data on patient sex, age, hypertension status, and tobacco use were collected and controlled for. Weather data was obtained from the National Centers for Environmental Information, using measurements from the Phoenix Airport Station matched to admission date. Extreme heat was defined as average temperatures above 90°F by FEMA. Logistic regression and multivariate analyses were conducted using R (version 4.3.2), with significance defined as p < 0.05.
Results: Of the total patient population, 3,670 were male and 9,727 female. 1,235 were diagnosed with ruptured IAs, and the remaining 12,162 with unruptured IAs.
Monthly fluctuations showed peaks in rupture occurrences in July and December, but these variations were not statistically significant (p=0.266). At average temperatures above 90°F, there was a 0.71% increase in rupture risk (RR) compared to temperatures between 80°F-90°F (p=0.019). Each 1°F increase above 90°F correlated with a 0.36% increase in RR when controlling for age, sex, hypertension, and tobacco use (p=0.028). Additionally, when maximum temperatures reached 100°F or higher, each 1°F increase was associated with a 0.69% increase in RR (p < 0.001).
Conclusion : Extreme heat should be considered a potential risk factor for aSAH. Contrary to studies in other regions, intracranial aneurysm rupture rates in Phoenix are not lower during summer. Temperatures above 90°F are significantly associated with higher aSAH rates.
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