How smoking can raise asthma risk for generations to come

By Mark Waghorn via SWNS

Dads who smoke around young sons raise asthma risk by nearly three-quarters - for their future grandkids - according to new research from Australia.

Children whose fathers were exposed to second-hand smoke when growing up are more prone to the breathing disorder.

And the danger further increases in cases where the offspring go on to become smokers themselves, according to the results from the University of Melbourne.

Passive smoking is believed to alter genes that pass down the generations. The mutations, carried in sperm, will be inherited by those who have not even been born.

Lead author Jiacheng Liu said: "We found the risk of non-allergic asthma in children increases by 59 percent if their fathers were exposed to second-hand smoke in childhood, compared to children whose fathers were not exposed.

"The risk was even higher, at 72 percent, if the fathers were exposed to second-hand smoke and went on to smoke themselves."

His team analyzed data from the Tasmanian Longitudinal Health Study (TLHS) - the largest and longest of its kind. It has tracked participants' respiration since 1968.

Co-lead author Dr. Dinh Bui explained: "Our findings show how the damage caused by smoking can have an impact not only on smokers but also their children and grandchildren."

"For men who were exposed to second-hand smoke as children, our study suggests they can still lower the risk they pass on to their own children if they avoid smoking."

The study included 1,689 boys - comparing those who had been diagnosed with asthma by the age of seven years.

It also looked at whether the fathers grew up with parents who smoked when they were under the age of 15 - and were current or former smokers.

Professor Shyamali Dharmage, head of TLHS, said: "We can't be certain of how this damage is passed on through generations, but we think it may be to do with epigenetic changes.

"This is where factors in our environment, such as tobacco smoke, interact with our genes to modify their expression. These changes can be inherited but may be partially reversible for each generation.

"It is possible tobacco smoke is creating epigenetic changes in the cells that will go on to produce sperm when boys grow up. These changes can then be passed on to their children."

About 1 in 12 people (about 25 million) have asthma, and the numbers are increasing every year, according to the CDC.

It is the most common long-term medical condition in children. Triggers include environmental factors, such as pollution.

Prof Jonathan Grigg, chair of the European Respiratory Society's Tobacco Control Committee who was not involved in the research, said: "Asthma is a common, long-term lung condition that affects children and adults and usually requires ongoing treatment.

"We already know smoking and being exposed to second-hand smoke can increase asthma risk.

"This study adds to growing evidence the damage caused by tobacco smoke can be passed on to children and even to grandchildren.

"We need to protect children from this damage with measures to discourage smoking and support to help smokers quit."

The findings were published in the European Respiratory Journal.