Published ahead of print on February 16, 2006, doi:10.1164/rccm.200509-1393OC Am. J. Respir. Crit. Care Med., Volume 173, Number 10, May 2006, 1098-1105 A more recent version of this article appeared on May 15, 2006
Submitted on September 7, 2005 Particulate Levels are Associated with Early Asthma Worsening in Children with Persistent DiseaseNathan Rabinovitch1*,1 Division of Allergy and Immunology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO, USA, 2 Division of Biostatistics, National Jewish Medical and Research Center, Denver, CO, USA * To whom correspondence should be addressed. E-mail: rabinovitchn{at}njc.org.
Rationale: Ambient particulate concentrations have been associated with variable physiological effects in children with persistent asthma taking controller medications. Objective: To determine whether exposure to particulate matter has immediate effects on asthma control in children with persistent disease. Methods and Measurements: In a school-based cohort, 73 children primarily with moderate and severe asthma were followed daily over one or two winters (2001-2002, 2002-2003) in Denver. The association between ambient fine particulate, bronchodilator use and urinary leukotriene E4 levels was assessed. Results: Daily concentrations of fine particulate peaked in the morning hours when children were commuting to school. In a multivariable analysis which controlled for meteorology, time trends and upper respiratory infections, an increase of one interquartile range (IQR) in morning maximum fine particulate levels was related to an average increase of 3.8% in bronchodilator usage at school (95% confidence interval (CI) = 0.2, 7.4%; p= 0.04). Children with severe asthma demonstrated significantly stronger associations (8.1% increase; 95% CI=2.9, 13.4%; p=0.003) than those with mild/moderate disease (1.6% increase; 95% CI=-2.2 to 5.4%; p=0.41; p=0.03 for difference between groups). Morning maximum fine particulate levels were also associated with urinary leukotriene E4 measured during school hours (average increase of 6.2% per IQR increase; 95% CI=1.9 to 10.5%; p=0.006). These associations were not discernable when 24-hour averaged concentrations were utilized. Conclusions: Peak concentrations of ambient fine particulate are associated with early increases in bronchodilator use and urinary leukotriene E4 levels among children with persistent asthma, despite the use of controller medications. Key words: Air pollution, PM2.5, severe asthma, children, LTE4
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