Household Incense Burning and Children's Respiratory Health: A Cohort Study in Hong Kong

Background: Incense burning is an important source of indoor air pollution in many Asian regions. We investigated the associations between household incense burning and lung function, lung function growth and respiratory diseases and symptoms in primary school children in Hong Kong.

Methods: A total of 4041 children (mean age: 9.1 years) were recruited from 27 primary schools in Hong Kong. Information on incense burning and medical history of respiratory diseases and symptoms was collected by questionnaire. Spirometry tests were performed to measure the children's lung function. A follow-up study was carried out after 1-year interval. Linear and logistic regression models were used to investigate the associations between incense burning, lung function, and lung function growth, and respiratory diseases and symptoms, respectively.

Results: At baseline, incense burning was associated with 48.6 mL/min [95% confidence interval (CI): -96.7, -0.5] lower maximum mid-expiratory flow (MMEF) in boys. In follow-up, incense burning was associated with reduced peak expiratory flow (PEF) growth in all participants. We also found that incense burning was associated with increased prevalence of bronchitis [odds ratio (OR) = 1.39, 95%CI: 1.11, 1.72] and bronchiolitis (OR = 1.72, 95%CI: 1.14, 2.56). Incense burning was also associated with higher prevalence of pneumonia (OR = 2.79, 95%CI: 1.10, 6.87) and wheezing (OR = 1.49, 95%CI: 1.08, 2.05) in boys, but not in girls.

Conclusions: We found that incense burning may adversely affect children's respiratory health. Further studies are warranted to elucidate the underlying mechanisms.