Sudden Death in the Bath in Kagoshima Prefecture in 2010 -Relationship between the Incidence of the Deaths and Ambient Temperature, Air Temperature Differences within a Day and Those from the Previous Day.

In Japan, sudden death in the bath (what is called ‘bath-related death’ ) has been reported to occur particularly in the elderly population in the winter. Our continuous investigations into bath-related death in Kagoshima Prefecture from 2006 to 2009 have shown that the death in Kagoshima occur at similar frequency as other prefectures in Japan. In this study, retrospective investigation of the inquest records in Kagoshima Prefecture in 2010 was performed in order to obtain the epidemiological data associated with bath-related death, especially, the relationship between the occurrence of the deaths and ambient temperature, air temperature differences within a day and those from previous day. The total number of the case was 199 (98 males and 101 females), which corresponds to a crude mortality rate of 11.7 per 100,000 person-year. The rate was the highest of the past 5 years. As previously reported, most deaths occurred during winter season (45.7%), particularly on cold days. There was a significant negative correlation between the occurrence rate of the deaths (the value indicates that the number of bath-related death is divided by the total number of the day at each temperature on weather observation spots) and ambient temperature including maximum, minimum and mean air temperature of the day. Particularly, deaths occurred frequently on the days when the maximum, minimum and mean air temperature was <18℃, <7℃, <13℃, respectively. Moreover, the occurrence rate of the deaths showed a significant positive correlation with air temperature difference within a day, and significantly increased on the days when the difference was more than 15℃. Further, the occurrence rate of the deaths showed a significant negative correlation with mean air temperature difference from the previous day when the temperature of the day was lower than that of the previous day, and significantly increased when the temperature dropped more than 3℃. In addition, the occurrence rate of the death in 2010 did not increase in the winter, but in the spring compared with those in 2009. In 2010, the average of the maximum temperature in the