Air pollution and family related determinants of asthma onset and persistent wheezing in children: nationwide case-control study

OBJECTIVE To identify risk factors (air pollution and family related) for the onset of asthma and persistent wheezing in children. DESIGN Nationwide case-control study. SETTING Denmark. PARTICIPANTS All Danish children born from 1997 to 2014 and followed for asthma onset and persistent wheezing from age 1 year to 15 years. MAIN OUTCOME MEASURE Onset of asthma and persistent wheezing. RESULTS A higher incidence of asthma was found in children of parents with asthma (adjusted hazard ratio 2.29 (95% confidence interval 2.22 to 2.35) and mothers who smoked during pregnancy (1.20, 1.18 to 1.22), whereas a lower incidence was found in children of parents with high educational attainment (0.72, 0.69 to 0.75) and high incomes (0.85, 0.81 to 0.89). Exposure to particulate matter