Association of atmospheric pressure fluctuations with hemorrhage subtype in spontaneous intracranial hemorrhage.

To investigate whether short-term changes in meteorological parameters are associated with hemorrhage subtype in patients presenting to the emergency department (ED) with spontaneous intracranial hemorrhage, with a particular focus on intraparenchymal hemorrhage (IPH) and subarachnoid hemorrhage (SAH). This single-center retrospective observational study included adults presenting to the ED between 2013 and 2022 with spontaneous intracranial hemorrhage confirmed on initial non-contrast computed tomography. Of 901 screened patients, 238 with IPH or SAH were included in the final comparative analysis. Clinical variables and meteorological data, including atmospheric pressure (AP), air temperature, and relative humidity, were recorded. Group comparisons were followed by univariable and multivariable logistic regression analyses. Because AP-related variables showed substantial collinearity, full, backward, and forward models were compared, and the final model was selected based on performance and parsimony. AP showed the most consistent association with hemorrhage subtype, whereas air temperature and relative humidity were not consistently related to either group. Event-hour mean AP was independently associated with SAH, whereas 3-day pre-event mean AP was independently associated with IPH. In the final forward multivariable models, headache remained positively associated with SAH, while lateralized neurological findings, systolic blood pressure, family history of hypertension, and 3-day pre-event mean AP were positively associated with IPH. Model discrimination was acceptable, with an area under the receiver operating characteristic curves of 0.789 for SAH and 0.823 for IPH. Short-term AP changes, rather than air temperature or relative humidity, were associated with hemorrhage subtype in this ED cohort. Further multicenter studies are needed to validate these findings and clarify underlying mechanisms.