The Effect of Minimum and Maximum Air Temperatures in the Summer on Heat Stroke in Japan: A Time-Stratified Case-Crossover Study

Abstract

An increase in the global surface temperature and changes in urban morphologies are associated with increased heat stress especially in urban areas. This can be one of the contributing factors underlying an increase in heat strokes. We examined the impact of summer minimum air temperatures, which often represent nighttime temperatures, as well as a maximum temperature on a heat stroke. We collected data from the records of daily ambulance transports for heat strokes and meteorological data for July and August of 2017–2019 in the Tottori Prefecture, Japan. A time-stratified case-crossover design was used to determine the association of maximum/minimum air temperatures and the incidence of heat strokes. We used a logistic regression to identify factors associated with the severity of heat strokes. A total of 1108 cases were identified with 373 (33.7%) calls originating in the home (of these, 59.8% were the age of ≥ 75). A total of 65.8% of cases under the age of 18 were related to exercise. Days with a minimum temperature ≥ 25 °C had an odds ratio (95% confidence interval) of 3.77 (2.19, 6.51) for the incidence of an exercise-related heat stroke (reference: days with a minimum temperature < 23 °C). The odds ratio for a heat stroke occurring at home or for calls for an ambulance to the home was 6.75 (4.47, 10.20). The severity of the heat stroke was associated with older age but not with air temperature. Minimum and maximum air temperatures may be associated with the incidence of heat strokes and in particular the former with non-exertional heat strokes.

Enhancing health resilience in Japan in a changing climate

“…103 A high proportion of elderly patients are transported by ambulances for heatstroke in Japan. 51 Environments with prolonged extreme heat have been linked to the increasing trend in the number of heatstroke cases among older adults, 44 , 48 , 57 , 104 , 105 with a high risk of symptom onset at home, including bedrooms. 50 A rise in ambient temperature has also been reported to increase the risk of out-of-hospital cardiac arrest.…”

A novel indicator for temperature control in heat stroke treatment

“…3 And up to 1.2 billion people worldwide will be at risk of a HS each year by the year 2100 if global warming continues at this rate. 4 Statistical data have shown that the incidences of HS and HS-induced deaths in China are increasing each year. However, the existing data are limited to some cities or provinces with small sample sizes, and large-scale HS epidemiology data are still lacking in our county or elsewhere in China.…”

“…Seriously, the morbidity rate of HS rises each year with global warming 3 . And up to 1.2 billion people worldwide will be at risk of a HS each year by the year 2100 if global warming continues at this rate 4 . Statistical data have shown that the incidences of HS and HS‐induced deaths in China are increasing each year.…”

Analysis of clinical characteristics and risk factors for patients with heatstroke in western China in 2022: a multicenter retrospective study

“…Temperatures are expected to continue to warm over time, and if global warming continues at this rate, up to 1.2 billion people worldwide will be at risk of heatstroke each year by 2100 9 . Many studies have discussed the relationship between maximum temperature and HS, revealing a signi cant correlation between the two 11,12 . That is, high temperatures contribute to the increased incidence of HS 12,13 .…”