Between 1959 and 1967, thousands of pregnant women in California sat down for interviews and described their diets, their days, and how much they and their husbands smoked and drank. They answered plainly. Nobody yet thought of tobacco or alcohol as a danger in pregnancy.
Six decades on, those answers are being put to a new use. A study in the journal Autism Research reports that men who were heavy drinkers or smokers when their wives were pregnant had grandchildren with a higher rate of autism spectrum disorder.
The data come from the Child Health and Development Studies, which has followed more than 15,000 California families across three generations of births. The new analysis covered 6,336 grandparents who had at least one of the exposures examined: tobacco, alcohol, coffee and tea.
What the numbers show
Grandchildren of men who drank five or more servings of hard liquor a week during their wife’s pregnancy were nearly three times as likely to be diagnosed with autism as grandchildren of non-drinkers. Tobacco followed a similar pattern. Men who used any form, whether pipes, cigars or cigarettes, had grandchildren with a 76 percent higher risk. For those who smoked 20 or more cigarettes a day, the risk was roughly double.
Adjusting for age, education and race did not erase the links. Coffee and tea showed nothing comparable, in either grandparent.
Heavy drinking by the father’s mother was also tied to higher autism risk, but very few grandmothers drank heavily, so the researchers said they could not rely on that result.
Barbara Cohn, the study’s senior author and director of the Child Health and Development Studies at the Public Health Institute, pointed to the era itself. Smoking and heavy drinking were near-universal among American men in the 1950s and 1960s. “Understanding risks that carry across generations may help explain why more children are being diagnosed with autism today given profound changes in environmental exposures and risky behaviors around the 1950s and 1960s,” she said.
How a grandfather’s habits might matter
The mechanism is unknown. One idea involves the germline epigenome, the chemical tags that help decide which genes are switched on. Chemical exposures may disturb those tags in the cells that become sperm, and the disturbance could persist into the next generation’s germline. In plain terms, a man’s habits around conception might leave a mark on reproductive cells that surfaces two generations later.
The design adds weight. This was a prospective study: habits were written down first, and diagnoses came decades afterward, so no one’s memory could have been colored by the outcome.
Limits worth keeping in mind
Only 86 grandchildren in the cohort had an autism diagnosis, 72 boys and 14 girls. That is enough to detect an association, but not enough for firm conclusions about combined exposures or about whether the effect runs through the mother’s line or the father’s. State disability records mostly capture children who need more support, so milder autism is probably undercounted. Wives reported the grandfathers’ habits, and some data were missing, although the authors tested for distortion and found their conclusions held. Other factors that were not measured could play a part.
The findings describe risk across a population. They do not explain why any one child is autistic, and they do not prove cause.
Still, early findings suggest a practical point. “The practical implication is that men planning to have children may have reason to quit smoking and drinking,” Cohn said. The study, led by M. Pearl, K. Berger and P. M. Cirillo among others, was supported by a Department of Defense autism research award and the Escher Fund for Autism. If researchers can find biological markers left by a grandparent’s exposures, they may be able to trace how the risk travels and where it can be interrupted. Anyone with questions about autism risk or about cutting back on tobacco and alcohol should talk to their doctor.
Sources
- Science Spotlight:Study Links Grandfathers’ Smoking and Drinking to Autism Risk in Grandchildren – Public Health Institute
- New Research: Grandfathers’ Smoking & Drinking Linked Autism Risk in Grandchildren | Explore Fiscal Sponsorship with PHI at APHA | Now Hiring
