Mysterious effects of smoking could appear even 3 generations later, study finds

The great-granddaughters of men who smoked cigarettes as prepubescent boys are more likely to carry excess fat on their bodies as young women decades later, according to a rather startling study.

The finding – which scientists say is one of the “first human demonstrations of the transgenerational effects of environmental exposure across four generations” – suggests that ancestral exposures to things like tobacco smoke may have consequences that linger. within families undetected for entire generations.

“If these associations are confirmed in other data sets, this will be one of the first human studies with appropriate data to begin to examine these associations and to begin to uncover the origin of potentially important intergenerational relationships,” says the researcher. epidemiologist Jean Golding from the University of Bristol in the UK.

In 2014, Golding and fellow researchers assessed data from the Avon Longitudinal Parent and Child Study (aka the “Children of the 90s” study), an observational study of pregnant women and their families, which began in the early 1990s and was initially led by Golding.

The 2014 analysis of questionnaire data from the Children of the 90s study found that sons of fathers who started smoking before age 11 were more likely to have a body mass index (BMI) higher in adolescence, with increased average waist circumference and full-body fat mass.

This, wrote Golding and his co-authors, was a rare example of a non-genetic transgenerational signal inherited by human offspring, much of the existing evidence for the effects of ancestral exposures coming from studies involving animal models.

Now, a deeper dive into the Children of the 90s dataset reveals that the phenomenon extends even further across generations, and not just from father to son, but from grandfather to his granddaughter, and also from a great-grandfather to his great-granddaughter.

“We now show that if the paternal grandfather started smoking before puberty [younger than 13], compared to later childhood (13-16 years), his granddaughters, but not his grandsons, had signs of excess body fat at two ages [17 and 24 years of age]“, explain the researchers in their new article.

“When the fathers of maternal grandfathers had started smoking before puberty, their great-granddaughters, but not the great-grandsons, had excess body fat [at 17 and 24].”

The researchers say a similar effect can be seen even when middle generations do not smoke regularly when they are under 13, highlighting a cross-generational effect across four generations.

“Before puberty, a boy’s exposure to particular substances can have an effect on the generations that follow him,” says Golding, noting that an important takeaway from the finding is the implications it a for our understanding of people’s health today, and how it can be shaped by unseen influences.

“One of the reasons why children become overweight may not have to do so much with their current diet and exercise as with the lifestyle of their ancestors or the persistence of associated factors over the years. .”

The team say we will need a lot more research into this phenomenon to understand what is going on here, and acknowledge that their own analysis has a number of limitations, including that there was a large amount of missing data in terms of respondents’ awareness of childhood and the situation of their parents and grandparents.

Nonetheless, they say their study offers unprecedented evidence of cross-generational effects, although how these effects occur is still largely unknown at this point.

It is possible that this is simply a correlation, and not an effect caused by exposure to tobacco smoke; the researchers acknowledge that it is vaguely possible that the prepubertal smokers in the study had an inherited predisposition to obesity that only surfaced a few generations down the line.

“It should be noted that the associations shown are related to obesity; it is generally recognized that obesity is a complex disorder caused by the interaction of genetic, epigenetic and environmental factors,” the researchers conclude.

“However, before hypotheses are generated as to the mechanisms by which the effects we have shown may have occurred, it is important to seek confirmatory evidence in other studies.”

The findings are reported in Scientific reports.

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