Risk factors of asthma in the Asian population: a systematic review and meta-analysis

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background and objective</jats:title><jats:p>An increasing trend of asthma prevalence was observed in Asia; however, contributions of environmental and host-related risk factors to the development of this disease remain uncertain. This study aimed to perform a systematic review and meta-analysis for asthma-associated risk factors reported in Asia.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We systematically searched three public databases (Web of Science, PubMed, and Scopus) in Feb 2021. We only included articles that reported environmental and host-related risk factors associated with asthma in the Asian population. Random-effect meta-analyses were conducted for frequently reported asthma-associated risk factors to provide an overall risk estimate of asthma development.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Of 4030 records obtained from public databases, 289 articles were selected for review. The most frequently reported asthma-associated risk factor was the family history of allergy-related conditions. The random-effect asthma risk estimates (pooled odds ratio,<jats:italic>OR</jats:italic>) were 4.66 (95% confidence interval (<jats:italic>CI</jats:italic>): 3.73–5.82) for the family history of asthma, 3.50 (95%<jats:italic>CI</jats:italic>: 2.62–4.67) for the family history of atopy, 3.57 (95%<jats:italic>CI</jats:italic>: 3.03–4.22) for the family history of any allergic diseases, 1.96 (95%<jats:italic>CI</jats:italic>: 1.47–2.61) for the family history of allergic rhinitis, and 2.75 (95%<jats:italic>CI</jats:italic>: 1.12–6.76) for the family history of atopic dermatitis. For housing-related factors, including the presence of mold, mold spots, mold odor, cockroach, water damage, and incense burning, the random-effect pooled<jats:italic>OR</jats:italic>ranged from 1.43 to 1.73. Other risk factors with significant pooled<jats:italic>OR</jats:italic>for asthma development included male gender (1.30, 95%<jats:italic>CI</jats:italic>: 1.23–1.38), cigarette smoke exposure (1.44, 95%<jats:italic>CI</jats:italic>: 1.30–1.60), cigarette smoking (1.66, 95%<jats:italic>CI</jats:italic>: 1.44–1.90), body mass index (<jats:italic>BMI</jats:italic>)–related parameters (pooled<jats:italic>OR</jats:italic>ranged from 1.06 to 2.02), various types of air pollution (NO<jats:sub>2</jats:sub>, PM10, and O<jats:sub>3</jats:sub>; pooled<jats:italic>OR</jats:italic>ranged from 1.03 to 1.22), and pre- and perinatal factors (low birth weight, preterm birth, and cesarean section; pooled<jats:italic>OR</jats:italic>ranged from 1.14 to 1.32).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>The family history of asthma was the most frequently reported risk factor for asthma development in Asia with the highest risk estimate for asthma development. This suggests a major role of the genetic component in asthma pathogenesis. Further study on asthma genetics is required to improve the current understanding of asthma etiology.</jats:p></jats:sec>