Relationship between the occurrence of spontaneous intracerebral hemorrhage and holidays and traditionally unlucky days in Fukuyama City, Hiroshima Prefecture, Japan.

To investigate whether calendrical information influences the occurrence of spontaneous intracerebral hemorrhage, we statistically compared the incidence of intracerebral hemorrhage for inpatients at Teraoka Memorial Hospital (164 patients), against various calendrical factors such as the day of the week, national holidays, and RokuYo (a recurring six-day series of lucky and unlucky days in the Japanese traditional calendar) over the period from January 1, 2001 to December 31, 2003. On Japanese national holidays the relative risk of intracerebral hemorrhage is significantly higher than on other days, certainly due to much more alcohol consumption on holidays. During RokuYo, the relative risk of intracerebral hemorrhage is extremely low on the traditionally unlucky days of ButsuMetsu and TomoBiki, as many Japanese people restrain their activities on these days. Certain days of the year and certain times of the Japanese supplemental calendars correlate significantly with the incidence of intracerebral hemorrhage.