Temperature and air pollution as risk factors for heat stroke in Tokyo, July and August 1980-1995.

Abstract

Heat stroke is associated with prolonged exposures to high air temperatures that usually occur in the summer months of July and August in Tokyo, Japan. Also during July and August, residents of Tokyo are often exposed simultaneously to high concentrations of air pollutants. To assess the impacts of these combined exposures, daily numbers of heat stroke emergency transport cases/million residents for Tokyo were stratified by gender and three groups: 0-14, 15-64; and > 65 years of age, for the months of July and August in 1980-1995. A regression model was constructed using daily maximum temperature (Tmax) and daily average concentrations of NO2 and O3 as model covariates. Classification indices were added to make it possible to compare the expected number of heat stroke cases by age and gender. Lag times of 1-4 days in Tmax and air quality covariates and terms to account for interactions between pairs of model covariates were also included as additional risk factors. Generalized linear models (GLMs), assuming a Poisson error structure for heat stroke emergency transport cases, were used to determine which covariates were significant risk factors for heat stroke for the three age groups of males and females. Same-day Tmax and concentrations of NO2 were the most significant risk factors for heat stroke in all age groups of males and females. The number of heat stroke emergency transport cases/million residents was greater in males than in females in the same age groups. The smallest number of heat stroke emergency transport cases/million residents occurred for females 0-14 years of age and the greatest number of heat stroke emergency transport cases/million residents occurred for males > 65 years of age.ImagesFigure 1Figure 2Figure 3Figure 4Figure 5

Effects of temperature and air pollutants on cardiovascular and respiratory diseases for males and females older than 65 years of age in Tokyo, July and August 1980-1995.

“…The model for the expected daily number of emergency transports per million for each cardiovascular and respiratory disease (ET) for males and females > 65 years of age is given as ln(ET) = Xβ, [1] where X is a matrix that includes a column of 1s for the intercept; classification variable columns for sex and for annual trends; columns for the daily values for T max and/or daily average concentrations for each air pollutant variable with lag times of 1-4 days; columns for interaction effects between pairs of model covariates as indicated from the correlation analysis given in Table 3; and β is the vector of model coefficients for each model covariate. Population changes from 1980 to 1995 have been included as an offset or normalizing factor in this model so that the expected daily number of hospital emergency transports are expressed as the expected daily number of hospital emergency transports per million.…”

“…Previous studies have examined exposures to daily maximum temperatures and air pollutant concentrations during the warm summer months of July and August in Tokyo and their effect on the daily number of hospital emergency transports per million for heat stroke (1) and three cerebral vascular diseases: cerebral hemorrhage, cerebral infarction, and cerebral ischemia (2). Both studies indicated that males and females > 65 years of age had the highest daily number of heat stroke and cerebral vascular disease hospital emergency transports per million of any age group to four Tokyo city hospitals.…”

Temperature variation in the 24 hours before the initial symptoms of stroke

“…Palavras-chave: acidente vascular cerebral, temperatura, risco cardiovascular, sazonal. The correlation between strokes and seasonal variations have been studied in various places [1][2][3][4][5][6][7][8] . Some studies around the world have reported an increase of incidence, mortality, and stroke hospitalization during the coldest months of winter.…”

Air temperature was associated with ambulance transports in Osaka area, Japan

“…Qiu et al reported that an unusually hot spell in 1999 was followed by a high mortality rate in Hokkaido, Japan [12]. Piver et al showed that heat stroke was associated with prolonged exposures to higher air temperatures that usually occur in the summer months of July and August in 1980-1995 in Tokyo [13]. In our previous study, higher air temperature was closely associated with higher ambulance transports in Takamatsu and Okayama city using monthly data [3,4].…”