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.
Highlights
Multiple factors contribute to the incidence of heat strokes; for example, environmental factors such as high temperatures and humidity, human factors such as dehydration, the presence of comorbidities, delayed heat acclimatization, aging and activity factors such as exercise and work in a hot environment [1]
Continued warming over time is expected [4] and up to 1.2 billion people worldwide will be at risk of a heat stroke each year by the year 2100 if global warming continues at this rate [5]
Sleep deprivation has been cited as a risk factor for a heat stroke and research on the health effects of nighttime temperatures associated with global warming and the heat island phenomenon will become increasingly important [38]
Summary
Multiple factors contribute to the incidence of heat strokes; for example, environmental factors such as high temperatures and humidity, human factors such as dehydration, the presence of comorbidities, delayed heat acclimatization, aging and activity factors such as exercise and work in a hot environment [1]. In. 2018, the number of people transported to emergency rooms for a heat stroke in Japan was. Continued warming over time is expected [4] and up to 1.2 billion people worldwide will be at risk of a heat stroke each year by the year 2100 if global warming continues at this rate [5]. A number of studies have been conducted on the relationship between maximum temperatures and heat strokes, reporting a strong correlation [6,7,8,9,10,11]. We previously noted a strong correlation between maximum temperatures and the number of emergency transports for heat strokes and were able to quantify the risk by temperature [12]. To date, most studies have focused on the maximum temperature
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