The frequencies and characteristics of heatstroke occurred in secondary/high schools were investigated by using the data of NAASH (National Agency for the Advancement of Sports and Health), and analysis was dune for a period of 10 years from 2005 to 2014. The investigated cities were Sapporo City, Sendai City, Tokyo City, Nagoya City, Osaka City, Hiroshima City, Fukuoka City, Kumamoto City and Kagoshima City in Japan. The environmental factors, e.g., outdoor temperature, relative humidity and global solar radiation, were obtained from the closest meteorological observatories from the respective cities at the time of occurrence.
During the 10-year period, out of 915,447 cases of accidents and injuries, 3,819 cases of heatstroke were reported in the data of NAASH for the investigated secondary/high schools of the cities. Of the 3,819 cases, 2,204 occurred at school grounds, e.g., schoolyard, gymnasium, pool and school building. Of the 2,204 cases occurred at school grounds, 1,430 occurred in the schoolyard, 557 in the gymnasium, 145 in the school building, and 26 were in the swimming pool. Out of 2,204 cases of heatstroke at school, 1,538 cases occurred during athletic club activities, 309 occurred on field day, 142 occurred during the physical education class.
The relationships between the environmental factors, i.e., outdoor temperature and WBGT (wet-bulb globe temperature) and the risk factor, i.e., the frequencies of heatstroke accidents and the odds ratio of heatstroke, were obtained. The risk factors of heatstroke for schoolyard, gymnasium, and school building, had a good correlation with WBGT, and this relationship would be used for the evidence when designing safe school environment. It showed that the odds ratio of heatstroke for schoolyard at 31 °C of WBGT was 7.09 based on the standard WBGT of 22 °C. On the other hand, the odds ratio for gymnasium at 31 °C of WBGT turned out to be 4.92 and that for school building 3.67. The rather high risk level for gymnasium and school house could be interpreted to mean the importance of indoor climatic control for avoiding heatstroke in schools.
As it can be seen in the number of heatstroke occurred during each class schedule, the frequencies of heatstroke during the athletic club activities were appreciably high for schoolyard and in gymnasium. It was confirmed that the frequencies of heatstroke of male students occurred on schoolyard was almost three times higher than those of female students. On the other hand, the frequencies of female students in gymnasium were somewhat greater than those of male students. These finding may indicate that the athletic club activities which mostly female students participate have a significant influence on the frequencies of heatstroke occurred in gymnasium.
The accidents of heatstroke on schoolyard during athletic club activities, physical education, and field day occurred most frequently at the grade of 31 °C WBGT. The frequencies of heatstroke occurred in gymnasium during athletic club activities passed its peak at the grade of 31 °C WBGT as well. The quasi-peak of frequencies in gymnasium during cultural club activities and cultural festival is, however, distributed in a wide range of WBGT.
The results of the frequencies of heatstroke during each sports club activities showed that the number of heatstroke occurred on schoolyard during baseball, basketball, and soccer was quite frequent. If the number of accident during each club activity is divided by the population of the concerned club, the determined accident ratio in gymnasium during female badminton club was the considerably the highest. Although badminton is played in gymnasium, the risk level during badminton under hot and humid condition would be equal to that of baseball or rugby on schoolyard.
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