Men exposed to secondhand smoke in childhood may pass lung problems to their own kids, study says

If men were exposed to secondhand smoke during childhood, their own children are more likely to have poor lung health, a new study has found.

Scientists have long known that exposure to secondhand smoke can have health consequences for non-smokers. But the new study suggests this impact goes far beyond the people directly exposed to secondhand or “passive” smoke, potentially affecting the next generation.

The study, which was published in the journal Thorax, underscores that the health problems tied to smoking can be “intergenerational”.

“These findings suggest that smoking may adversely affect lung function not only in smokers but also in their children and grandchildren,” the researchers wrote.

The study included 890 fathers whose children were born in early 1960s Australia, with researchers following the pairs until the children were aged 53 in the 2010s.

They found that fathers who had been exposed to secondhand smoke in their own childhoods – meaning at least one parent smoked at least six days per week before they reached puberty – were more likely to have children with lung health problems that lasted well into adulthood.

By age 53, these children were 56 per cent more likely to have poor lung function, measured as forced expiratory volume in one second (FEV1), which is the amount of air someone can forcefully exhale in one second.

They were also more likely to have signs that their lung function was decreasing quickly – even if they did not yet meet the criteria for chronic obstructive pulmonary disease (COPD), which is one of the leading causes of death globally.

“Impaired lung function may begin long before respiratory illnesses become clinically apparent,” Shyamali Dharmage, one of the study’s authors and a professor in the allergy and lung health unit at the University of Melbourne in Australia, told Euronews Health.

The effects held up after the researchers accounted for other factors that might explain the connection, such as socioeconomic status and parents’ history of asthma. They were even stronger if the children had also been exposed to secondhand smoke during childhood.

Notably, nearly 69 per cent of the fathers and 57 per cent of their children were exposed to secondhand smoke in childhood. About half of the children had been smokers at some point in their lives as well.

But the researchers found that the children’s own exposure to secondhand smoke could explain just 10 per cent of the relationship between their lung health problems and their fathers’ exposure to smoke.

The findings are in line with previous research that shows that children could be at higher risk of developing asthma if their parents were exposed to secondhand smoke in their own childhoods.

The analysis was from an observational study, meaning the researchers cannot prove that fathers’ secondhand smoke exposure directly caused their children’s poor lung health. They said other unknown factors, such as genetics, could also play a role.

But they offered a few possible explanations. For example, if boys are exposed to the “harmful substances” in cigarettes before they reach puberty, it may alter the genetic expression of their developing sperm cells, affecting what traits are passed down to their own children, the researchers said.

Whatever the mechanism, the researchers urged fathers to try to break the intergenerational cycle by avoiding smoking around their children.

“Protecting children from passive smoke could benefit not only their own respiratory health but also that of their offspring,” Dharmage said.