Asthma in babies: risk higher if fathers smoke during mother’s pregnancy, study shows
- A Taiwanese study looked at paternal smoking during pregnancy and its effects on immune system genes
- More than 1,600 babies were involved in the study, and 756 of those were followed for six years
Babies have a greater risk of asthma if their father smoked before their birth, according to a new study of Taiwanese families.
The research, published today in Frontiers in Genetics to coincide with the World Health Organisation’s World No Tobacco Day, also reveals how immune genes can predict the level of risk.
More than 1,600 Taiwanese couples with newborn babies took part in the study which analysed their lifestyle and genetic make-up.
Exposure to tobacco smoke during development is already known to harm children in many ways, and non-coding ‘epigenetic’ changes to DNA have been repeatedly found.
However, this is the first study to show that, just like maternal smoking or air pollution, paternal smoking during pregnancy can program epigenetic modifications in important immune system genes and these modifications increase the associated risk of childhood asthma.
“We found that prenatal exposure to paternal tobacco smoking is associated with increased methylation of certain immune genes, which alters how the genetic code is read,” says lead author Dr Wu Chih-chiang of Po-Jen Hospital in Kaohsiung, Taiwan.
“This smoking associated DNA methylation is significantly retained from birth to six years of age, and correlates with development of childhood asthma.”
There is no cure for asthma, a condition in which the airways narrow and swell and produce extra mucous. It makes breathing difficult and triggers coughing, wheezing and shortness of breath.
The researchers followed 1,629 children from birth to 18 months old and 756 of these until the age of six. They were regularly assessed and given a DNA analysis.
Twenty-three per cent of the fathers were smokers, compared to just three per cent of the mothers.
Infants with prenatal parental tobacco smoking exposure had a significantly higher risk of asthma by the age of six than those without.
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“Children with prenatal parental tobacco smoking exposure corresponding to more than 20 cigarettes per day had a significantly higher risk of developing asthma than those with fewer than 20 cigarettes per day,” reports senior author Dr Kuender Yang of Mackay Children’s Hospital in Taipei.
More striking, however, were the results of the DNA analysis.
The higher the parental tobacco smoking exposure dose, the higher the level of methylation of LMO2, IL10 and GSTM1 – the genes known to have key roles in immune function.
And the higher the methylation level, the higher the associated risk of asthma.
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“It remains to be determined whether the DNA methylation associated with parental tobacco smoking originated from tobacco smoke exposure in utero, from preconception changes to the father’s sperm, or if there is an alternative explanation,” Dr Wu says.
Researchers hope future studies can clarify the relationship and find ways to reverse the genetic changes.