2026 Volume 54 Issue 2 Pages 69-75
The incidence of stroke varies depending on the meteorological conditions on the day of onset. This study aimed to clarify the characteristics of meteorological conditions associated with the onset of spontaneous subarachnoid hemorrhage (SAH). We retrospectively analyzed patients with spontaneous SAH who were newly registered at our institution over a 10-year period from January 2014 to December 2023. Meteorological data for Osaka City, including atmospheric pressure (local and sea level), humidity (mean and minimum), and temperature (mean, minimum, maximum, and net effective) were obtained from the Japan Meteorological Agency website. Each meteorological parameter was defined as “extremely low” (< 10th percentile), “low” (< 33.3rd percentile), “normal” (33.3rd–66.6th percentile), “high” (> 66.6th percentile), or “extremely high” (> 90th percentile). The association between these meteorological variables and SAH onset was also evaluated.
A total of 281 patients with SAH were included, of whom 169 were female (60.1%). The average age was 62.1±15.6 years. The onset of SAH was significantly associated with daily changes in minimum and net effective temperatures (p = 0.043 and 0.023, respectively). The incidence of SAH was significantly higher when the net effective temperature was low or extremely low compared with the previous day (p = 0.0004 and 0.0002, respectively). No significant associations were found between the onset of SAH and the atmospheric pressure or humidity. Similarly, the incidence of aneurysmal SAH was significantly higher under low or extremely low net effective temperature conditions relative to the conditions on the previous day (p = 0.0007 and 0.0002, respectively).
A higher proportion of days of SAH onset was observed after a decrease in the net effective temperature from the previous day. These findings suggest that exposure to sudden cold conditions may contribute to the onset of spontaneous SAH.
