Smoking during pregnancy results in an increased risk of asthma even in adulthood

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Exposure to cigarette smoke is known to increase the risk of asthma in childhood, but research findings on its later effects are scarce. A study investigated 5,200 individuals born in Northern Finland in 1966. The mother's smoking during pregnancy resulted in an approximately 1.5-fold asthma risk in the child in adulthood, at the ages between 31 and 46. The risk was higher for those who had reported suffering from respiratory symptoms previously or who were carriers of the RUNX-1 susceptibility gene.

"The findings may point to the early vulnerability of the airways and permanent harm caused by cigarettes," says Docent Sanna Toppila-Salmi from the University of Helsinki and the Hospital District of Helsinki and Uusimaa.

According to Toppila-Salmi, families planning for a pregnancy and expectant mothers should be encouraged to give up smoking. This would lower the risk of adult-onset asthma in their children and improve the health of the airways.

The study was carried out collaboratively by the University of Helsinki, the University of Oulu and the National Institute for Health and Welfare.

Abstract
Rationale: Environmental tobacco smoke exposure (ETS) increases asthma risk in children. There is limited knowledge of prenatal ETS for adult onset asthma.
Objectives: To determine the association between prenatal ETS and adult onset asthma.

Measurements and main results: Questionnaire and clinical data of 5200 people, free of physician-diagnosed asthma by the age 31 years, of Northern Finland Birth Cohort 1966 Study was used. The association of maternal smoking during the last three months of pregnancy with onset of physician-diagnosed asthma and with lung function in adult offspring were studied by adjusted multivariate regression analyses. The cumulative incidence of physician-diagnosed asthma between the ages of 31 and 46 years was 5.1% among men and 8.8% among women. Gestational smoke exposure was associated with adult onset asthma among the offspring (adjusted odds ratio 1.54, 95% confidence interval 1.04–2.29), namely among offspring who reported either past non-diagnosed asthma (odds ratio 9.63, 95% confidence interval 2.28–40.67), or past cough with wheeze (3.21, 95% CI 1.71–6.05). Significant association was detected between gestational smoke exposure and offspring's FEV1/FVC ratio at 31 years of age. In offspring with the haplotype rs11702779-AA of RUNX1 gestational smoke exposure was associated with adult onset asthma (5.53, 95% CI 2.11–14.52, adjusted p for interaction 0.10).
Conclusions: Maternal smoking during pregnancy is associated with the cumulative incidence of asthma in offspring between 31 and 46 years. The association was accentuated in offspring who reported at age 31 as having past respiratory problemsand/or, who had haplotype rs11702779-AA. Also a reduction in FEV1/FVC ratio was observed at age 31 years in offspring with gestational smoke exposure. These results could reflect early vulnerability of offspring's airways to ETS and its putative long-term effects.

Authors
Sanna Toppila-Salmi, Annika T. Luukkainen, Baizhuang Xu, Jussi Lampi, Juha Auvinen, Kishor Dhaygude, Marjo-Riitta Järvelin, Juha Pekkanen

University of Helsinki material

European Respiratory Journal abstract

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