Abstract
Background: The factor most greatly affecting the incidence of stroke is atmospheric temperature. Incidences have been reported to be the highest in winter and the lowest in summer, but this is not necessarily consistent. This is because meteorological effects are complex, and furthermore, problems have been pointed out in the research methodology, such as limited periods of observation and limited study population sizes.
Method: The subjects of the present study were 46,031 stroke patients who were admitted to the Rosai General Hospitals located in various cities in Japan for medical treatment from the 2002 fiscal year to the 2008 fiscal year. The number of incidences were compared by month and by type of stroke. For meteorological classification, four regional groups were studied.
Results: The incidence of cerebral hemorrhage was low in summer and high in winter for both males and females, with the lowest month differing by one month between Northern and Western Japan. The incidence of subarachnoid hemorrhage was high in females and was low in summer and higher from autumn to winter. The incidence of cerebral hemorrhage did not show an evident seasonal difference. The incidence of both lacunar infarction and atherothrombotic infarction showed a bimodal distribution with a rapid increase in summer and a repeat increase in January. Cardioembolic infarction showed a high incidence only in winter.
Conclusion: Measures should be taken to prevent stroke, taking into consideration not only the living environment but also the occupational environment that accompanies changes in the global environment.
