Objective: To investigate the relationship between hair nicotine levels at 15 months of age and prior parent-reported smoking exposure, and the risk of wheezing and current asthma from 15 months to 6 years of age.
Study design: We measured hair nicotine levels at 15 months of age in 376 of 535 infants enrolled in a prospective birth cohort in Christchurch, New Zealand. We obtained detailed information from parents about smoking exposure during pregnancy and in the home at 3 and 15 months of age. Data for demographics, wheezing, and asthma were obtained from yearly questionnaires up to age 6 years. We assessed hair nicotine levels in relation to reported smoke exposure in pregnancy and up to age 15 months, and the association between high levels of hair nicotine and annual reports of current wheeze and current asthma using multiple logistic regression.
Results: Hair nicotine increased with numbers of smokers and daily cigarettes smoked at home, and was also strongly associated with smoking in pregnancy. High level of hair nicotine was associated with increased risk of wheeze (Odds ratio 2.30, P = 0.001) and, though not significant, of current asthma (Odds ratio 2.02, P = 0.056) at 15 months of age, after controlling for socio-economic status, ethnicity, body mass index, respiratory infections in the first 3 months of life, and duration of exclusive breastfeeding. At older ages the associations were non-significant.
Conclusion: In children aged 15 months hair nicotine level was related to smoking exposure, and was associated with increased risk of wheeze and asthma.
Keywords: asthma & early wheeze; cohort studies; environmental exposure; epidemiology; nicotine analysis; risk factors; tobacco.
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