Granny’s smoking increases grandchildren’s risk of asthma
Children may have a forty per cent higher chance of developing asthma if their grandmother smoked whilst pregnant.
Asthma rates have been increasing over the last fifty years and health researchers are piecing together the many factors that might explain it.
Speaking this week at the European Respiratory Society International Congress in Amsterdam, scientists have reported that some children whose grandmothers smoked during pregnancy could have as high as forty per cent increased risk of developing asthma.
"For us to understand more about the asthma epidemic, we require a greater understanding of how harmful exposures over your lifetime may influence the disease risks of generations to come,” says lead scientist Dr Caroline Lodge in a press release from the European Lung Foundation.
Lodge conducted the research whilst working at Umeå University, Sweden.
A big effect on kids who develop asthma early on
The work was presented by co-author Professor Bertil Forsberg, from Umeå University, Sweden. He describes how they categorised the children’s asthma into three groups:
First, those who developed asthma before the age of three, the so-called early onset group. Second, the late onset group who developed asthma after the age of three. Third, those who developed asthma before the age of three, and were still suffering from it between four and seven years of age--the so-called early onset persistence group.
“Smoking doesn’t affect the late onset group at all. For this group, neither the mothers or grandmothers smoking habits had any effect on the rates of childhood asthma,” says Forsberg.
“But in the early onset persistence group, the risk of developing asthma increased by about forty per cent if the Grandma smoked during her pregnancy,” he says.
This applied to children even if their own mother had not smoked during her pregnancy.
Grandma’s smoking habits twice as important as mum’s
The study is based on information from the Swedish Health Registry and includes almost 45,000 grandmothers who were pregnant with girls between 1982 and 1986.
“We see that grandmother’s smoking habits affected childhood asthma rates twice as much as the mother’s own smoking habits,” says Forsberg.
He describes the new research as distinct from previous studies in the same area due to the type of data they used.
“For the first time we’ve used prospective data on the grandmother’s smoking habits, collected by their midwifes during the grandmother’s first trimester, and recorded in the Swedish health registers” says Forsberg.
“In previous studies they relied on the mother’s recollection of whether or not their own mother had smoked during pregnancy--so this new registry data should be much more reliable,” he says.
Scientists yet to investigate the risks in boys
So far, they have looked at the female line of the family, but Forsberg suggests that future work will also consider the male line, and the effects of other sources of nicotine.
"The next step is to look at the male line, but we also plan to look at other types of nicotine exposures--where you are exposed without actually smoking, such as snuff and even e-cigarettes. We will find out if there are risks associated with these alternative sources of nicotine,” said Forsberg.
According to both Lodge and Forsberg, the new results may help scientists understand the inherited risk of diseases associated with other environmental exposures beyond smoking.