This Could Be Why You Have Asthma

by Katherine Don

Women get a lot of flack about their health choices while pregnant, from eating sushi to having that morning cup 'o Joe. Same goes when it comes to our vices. Need a drink? That’s a big no-no, since drinking — especially heavy drinking — can increase your child's risk of birth defects (and more). Want a cigarette? Better hold off — smoking increases your kid’s chances of low birth weight and respiratory illnesses. And now there's this: Smoking while pregnant could give your grandchildren asthma, too. According to new research presented at the European Respiratory Society’s International Congress last week, you're 10 to 22 percent more likely to develop asthma if your grandma smoked while pregnant. So yeah, it looks like mommy guilt isn't the only thing we've got to watch out for; grandmommy guilt could be a thing, too.

For the study, researchers analyzed data from the Swedish Registry, which included 44,853 grandmothers and data on 66,271 grandchildren. It just so happened that the registry included information about smoking habits and asthma medication, so it was a gold mine of information for researchers looking for links between a grandparent's smoking habits and their grandkids' health. And the data basically confirmed their hunch.

The study's findings were yet another reminder that many of our behaviors today could have terrible health consequences for our kids, and their kids, and their kids ad infinitum. That’s pretty terrifying. It also makes me wonder if I should climb into an underground bunker and do nothing all day. What if my laptop is currently emitting some sort of radiation that will ruin the life of my great-great-great grandchild?! (And if you think I'm exaggerating on that one, guess what: Laptops do emit electromagnetic frequencies at levels a National Institutes of Health study calls "not negligible.") But I digress.

Turns out that this somewhat bizarre finding might change the way scientists think about the genetic transmission of health problems. As we all learned in high school biology, genetic traits are passed down from grandparent to parent to grandkid. But increasingly, scientists are learning that traits seem to be epigenetic, meaning that although a trait is indeed inherited, the inheritance arrived because during development, the gene was affected by external environmental factors, such as smoking.

So how exactly does Grandma’s love for lighting up cause a grandkid to have asthma decades later? As explained by Nathan Collins at Pacific Standard, “the rough idea is that smoking affects not only a fetus' genes, but also the reproductive material — the eggs, that is — already under development in a fetus while still in the womb.”

In other words: Grandma's smoking most likely affected Mom's little developing eggs, and those eggs later provided the genetic material for that her kids (a.k.a. you). Put that that way, it kind of makes your head spin, no? According to Dr. Caroline Lodge, one of the study’s authors, this finding suggests that the behaviors of one generation can affect multiple generations down the road:

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.

The study’s authors hypothesize that this might partially explain why asthma incidence is on the rise: Smoking was common when the grandmas from the Swedish Registry data were pregnant. The latest numbers from the National Center For Health Statistics show that the incidence of asthma rose from 7.3 percent in 2001 to 8.4 percent in 2010. It's weird to think that our grandmas might have something to do with this, but this new finding shows that this is at least a possibility.

But wait! There is a silver lining. According to this logic, asthma might become less common in a couple of decades, when Gen Z decides to have grandkids, because the incidence of smoking is actually decreasing. (So, yay?) OK, that may not be a huge silver lining, I suppose — it’s more of a smoky-grey one — but hey, it's something.

Image: Toni Blay/Flickr