Modifying Effect of Age on the Association between Ambient Ozone and Nighttime Primary Care Visits Due to Asthma Attack

Shin Yamazaki,Hiroshi Nitta,Masayuki Shima,Michiko Ando

doi:10.2188/jea.je20081025

Abstract

BackgroundWe examined the association between short-term exposure to outdoor air pollution and nighttime primary care visits due to asthma attack. We also investigated the modifying effects of age on this association.MethodsA case–crossover study was conducted at a primary care clinic in metropolitan Tokyo. The subjects were 308 children aged 0–14 years and 95 adolescents and adults aged 15–64 years. All subjects made visits to the clinic for an asthma attack at between 7 PM and 12 AM. Data on hourly concentrations of particulate matter with a 50% cut-off aerodynamic diameter ≤2.5 µm (PM2.5), ozone, and nitrogen dioxide (NO2) were obtained. A conditional logistic regression model was used to estimate odds ratios (ORs) of primary care visits per unit increment of each air pollutant.ResultsAmong children, the ORs in warmer months per 10 ppb increment of the 24-hour mean concentration of ozone were 1.16 (95% confidential interval [CI], 1.00–1.33) adjusted for temperature, and 1.29 (95% CI, 1.08–1.55) adjusted for PM2.5, NO2, and temperature. With respect to modification of the association by age, the ORs for 24-hour mean concentration of ozone—after adjustment for PM2.5, NO2 and temperature in warmer months—in children aged 0–1 years, 2–5 years, and 6–14 years were 1.06 (95% CI, 0.63–1.78), 1.37 (95% CI, 1.05–1.71), and 1.25 (95% CI, 0.87–1.82), respectively. There was no association between ozone and primary care visits among adults.ConclusionsAn association was found between ozone and nighttime primary care visits for asthma attack in warmer months; the association was greater among preschool children.

Highlights

Children’s exposure to air pollution is a special concern because their immune system and lungs are not fully developed
Children are considered to be more sensitive to air pollution than adults,[4] and asthmatic children are vulnerable to the adverse health effects of air pollution
In our analysis we first converted the hourly air pollution data into 6-hour mean concentrations, and we examined the associations between the 6-hour mean concentrations of each air pollutant and the risk of nighttime primary care visits due to asthma attack

Summary

Introduction

Children’s exposure to air pollution is a special concern because their immune system and lungs are not fully developed. Studies of asthmatic children conclude that exposure to high concentrations of O3 or PM significantly increases the risk of respiratory symptoms and asthma medication use, and diminishes lung functions such as peak expiratory flow rate and forced expiratory flow rate.[5,6,7,8,9] among children, age-related sensitivity to air pollutants and adverse respiratory effects has been investigated in only a small number of studies. We examined the association between short-term exposure to outdoor air pollution and nighttime primary care visits due to asthma attack. Conclusions: An association was found between ozone and nighttime primary care visits for asthma attack in warmer months; the association was greater among preschool children

Methods

Results

Conclusion