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

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 simulta neously 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 group s: 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 temperat ure (T-max) and daily average concentrations of NO2 and O-3 as model covari ates. 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 da ys in T-max and air quality covariates and terms to account for interaction s between pairs of model covariates were also included as additional risk f actors. Generalized linear models (GLMs), assuming a Poisson error structur e for heat stroke emergency transport cases, were used to determine which c ovariates were significant risk factors for heat stroke for the three age g roups of males and females. Same-day Tm, and concentrations of NO2 were the most significant risk factors for heat stroke in all age groups of males a nd females. The number of heat stroke emergency transport cases/million res idents was greater in males than in females in the same age groups. The sma llest number of heat stroke emergency transport cases/million residents occ urred for females 0-14 years of age and the greatest number of heat stroke emergency transport cases/million residents occurred for males > 65 years o f age.