A new study has found that children are significantly more likely to develop asthma if their father was exposed to tobacco smoke as a child.
And they are at even greater risk of developing the common lung disease if their father was a smoker himself, according to an international team of researchers.
The findings, published in the European Respiratory Journal, provide further evidence of the possible existence of a “transgenerational effect”, in which smoking can harm the health of people born two generations later.
“We found that the risk of non-allergic asthma in children increased by 59% if their parents were exposed to secondhand smoke during childhood, compared to children whose parents were not exposed.
“The risk was even higher, 72%, if the parents were exposed to secondhand smoke and started smoking themselves,” said Jiang Liu of the University of Melbourne, one of the co-authors.
The study was conducted by a team of researchers from Australia, Great Britain and Sri Lanka.
Dr Ding Bui, another co-author, said: “Our results show how the harm caused by smoking can affect not only smokers but also their children and grandchildren.”
Given their findings, men should try to avoid smoking if at all possible to reduce the risk of affecting the health of their own sons or their offspring, Bui added.
John Foster, health policy manager at Asthma + Lung UK, said: “This research is truly shocking, showing that the negative effects of smoking can last for generations. The fact that children born today have a 59% higher risk of developing asthma if their father was exposed to second-hand smoke as a child shows the huge impact smoking has on other people’s health.”
The findings are based on the researchers’ analysis of detailed health data from 1,689 pairs of parents and their offspring collected as part of the long-term Tasmanian Longitudinal Health Study in Australia.
The paper says: “Our results suggest that when boys are passively exposed to their parents’ tobacco smoke before the age of 15, their offspring have an increased risk of nonallergic childhood asthma, but not allergic asthma.
“Exposure to parental smoke before age 15 is a major risk factor for the development of nonallergic asthma.”
Professor Jonathan Grigg, chairman of the European Respiratory Society’s tobacco control committee, who was not involved in the study, said it added to the evidence of intergenerational smoking risks.
He said children must be protected from further harm if ministers take further action to stop smoking. He called for an increase in stop-smoking services and for adults to be regularly asked at NHS appointments whether they smoked and offered help to quit if they did.
Bui said epigenetic changes caused by smoking — modifications to genes in which the sequence of a person’s DNA does not change — were the most likely reason for the significantly increased risk of asthma in children whose parents were exposed to secondhand smoke when they were young.
“Epigenetic changes can be caused by environmental exposures, such as smoking, and can be passed down to the next generation. Specifically, when a boy is exposed to tobacco smoke, it can cause epigenetic changes in his gametes. These are the cells that go [on] produce sperm.
“These changes will later be passed on to his children, which in turn can harm their health, including increasing the risk of developing asthma. In boys, germ cells continue to develop until puberty, and this is a vulnerable period when exposure to tobacco smoke can affect the cells and cause epigenetic changes,” Bui said.