The relation between ambulance transports stratified by heat stroke and air temperature in all 47 prefectures of Japan in August, 2009: Ecological study

Objective Our aim was to investigate the link between ambulance transports stratified by heat stroke and air temperature in August 2009 in Japan. Methods Monthly observations for ambulance transports stratified by heat stroke in August 2009, in all 47 prefectures of Japan were obtained from the Ministry of Internal Affairs and Communications. Daily air temperature data from the Japan Meteorological Agency in August 2009 for all 47 prefectures in Japan were also used. The effect of high air temperatures on ambulance transports stratified by heat stroke was analyzed in an ecological study. Results Various air temperature parameters , i.e., the mean of the mean air temperature, mean of the highest air temperature, mean of the lowest air temperature, the highest air temperature, and the lowest air temperature in August 2009 were significantly and positively correlated with ambulance transports stratified by heat stroke (per total number of ambulance transports and per 10,000 persons) in the 47 prefectures of Japan. The correlation coefficient between the mean of the highest air temperature in August 2009 and ambulance transports stratified by heat stroke (per 10 000 persons) was the highest among the examined parameters (r = 0.799, p<0.0001). Conclusion Higher air temperatures were closely associated with higher numbers of ambulance transports stratified by heat stroke in August 2009 in Japan.