Grandmother's smoking habits increase asthma risk in grandchildren

The new study, presented today (30 September, 2015) at the European Respiratory Society's International Congress, 2015, is the first to investigate the risk in a whole population and use evidence about smoking habits taken directly from grandmothers at the time they were pregnant.

There has been a rapid increase in asthma in the last 50 years. Changing environmental exposures are thought to be responsible for this and more recently researchers are looking at these exposures in previous generations. It is known that tobacco use can affect the activity of genes and the researchers in this new study hypothesised that these changes could then be passed to subsequent generations.

Researchers investigated whether smoking in grandmothers, while they were pregnant with daughters, was linked with an increased risk of asthma in their grandchildren. Data was taken from the Swedish Registry and included 44,853 grandmothers from 1982 to 1986. Smoking exposure was recorded during pregnancy and use of asthma medication was recorded in 66,271 grandchildren.

The results found that if grandmothers had smoked whilst they were pregnant, there was an increased risk of asthma in grandchildren, even if their mothers had not smoked during pregnancy. The risk of asthma was increased by 10 to 22%.

Dr Caroline Lodge, an author of the study and Research Fellow at the University of Melbourne, Australia, said: "We found that smoking in previous generations can influence the risk of asthma in subsequent generations. This may also be important in the transmission of other exposures and diseases."

"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. Additionally, researchers in this area need to be aware, when interpreting the asthma risk from current exposures and genetic predisposition, that individuals may carry an inherited, non-genetic, risk from exposures in previous generation. This knowledge will help to clarify the findings concerning current risk factors in asthma research."

Professor Bertil Forsberg, presenting author of the study from Umeå University, Sweden, said: "The next stage for the research team is to investigate the potential inheritance of asthma risk through the male line, by assessing the risk of asthma in grandchildren whose grandmothers smoked whilst pregnant with their fathers. The findings also encourage research into inherited disease risks for other environmental exposures."