Wheeze During the First 18 Months of Life: A Prospective Cohort Study to Explore the Associations With Indoor Nitrogen Dioxide and Formaldehyde—Preliminary Results

Abstract

O-30A7-4 Background/Aims: To examine whether exposures to nitrogen dioxide (NO2) and formaldehyde at home increase the risk of wheezing in the first 18 months of life. Methods: Young infants born in Hong Kong during 1 April 2008 to 31 March 2009 were recruited from Maternity and Child Health Centers into a prospective cohort. Parents were interviewed with the modified International Study of Asthma and Allergies in Childhood questionnaire to obtain baseline information on respiratory health, as well as family and home environment characteristics when the infants were 4 months old. The indoor air levels of NO2 and formaldehyde were measured in the bedrooms of the infants at 5 months. With the aid of a respiratory health diary parents recorded and reported respiratory symptoms and illnesses of the infants until they were 18 months old through monthly telephone interviews. New onset wheezing was used as outcomes, and Cox proportional hazards model was used to document the effects of NO2 and formaldehyde on the risk of wheeze after adjusting for possible confounders. Results: Of the 544 infants recruited into the cohort with baseline exposure measurements on NO2 and formaldehyde, 179 have been followed up to 18 months by mid-March 2010, and 31 (17.3%) reported new onset wheezing during follow-up. In the Cox model adjusted for gender and family history of asthma, exposure to indoor formaldehyde was significantly associated with new onset wheezing. The result indicated that for every 10 μg/m3 increase in formaldehyde concentration, the risk of new onset wheezing increased by 5.1% (95% CI: 1.1%–9.3%). NO2 did not appear to have an independent effect on the outcome. Conclusion: Indoor formaldehyde exposure was associated with the new development of wheezing in the first 18 months of life.