Why More Firstborn Kids Need Glasses

By Elizabeth Preston | October 14, 2015 10:29 am

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It’s bad enough for the first kid when a new baby shows up to steal your thunder. But the injustice is compounded when you have to start wearing glasses while your little sibling stays as cute and non-four-eyed as ever. If this sounds familiar, you’re not alone: firstborn kids are more likely to be nearsighted. Part of the reason might be that they get more education.

A study in the United Kingdom and Israel found that myopia—that’s nearsightedness, if you’re one of those lucky people who hasn’t spent much time at the optometrist’s office—is about 10% more common in firstborn children. But that study only looked at subjects between 15 and 22 years old. Is this a new issue, or have older siblings always gotten the short end of the eyesight stick?

To find out, researchers in the UK gathered data from nearly 90,000 subjects. These people were part of a huge national project called the UK Biobank, which is tracking the health of about half a million adults. For this vision study, the scientists—Jeremy Guggenheim of Cardiff University and Cathy Williams of the University of Bristol—looked only at white adults between 40 and 69 years old. Overall, about 30% of them were myopic.

After controlling for age and sex, the researchers saw that first children were about 12% more likely to be nearsighted than second children. This was similar to the finding of the earlier study with younger subjects. Firstborns were also 21% likelier than second-borns to have severe myopia. And when compared to people born fourth or later, firstborns were almost 40% more likely to be nearsighted. (The researchers counted only children as firstborns too, but the results were the same when they removed only children from the analysis.)

Earlier research suggested that parents spend more resources on educating their oldest children than other kids. So Guggenheim and Williams adjusted their analysis for how many years of education people had received. This took away about a quarter of the extra myopia in firstborns.

The authors think this means education is a factor. They couldn’t specifically study anyone’s early childhoods to see how much time they had spent outdoors (which is good for the eyes) versus reading and studying (not so good). But it seems that somewhere along the way to completing their longer educations, oldest siblings were more likely to end up with glasses.

It wasn’t a large effect. The difference between firstborns and everyone else averaged out to less than –0.25 diopters in a glasses prescription. (Again, for those of you who aren’t experts, 0.25 is usually the smallest increment by which an eye doctor adjusts your prescription.) And since accounting for education only removed some of this difference, there must be other factors involved. The authors say these likely include social factors, birthweight, and time spent outside.

In many parts of the world, people’s eyes have gotten worse in recent decades. This has been especially dramatic in East Asia. Spending a lot of time on “near work,” such as reading, is a known risk factor. So is spending less time outdoors. Even among the subjects in this study, who were 40 to 69 years old, myopia was more common in younger people.

No matter how much you shun schoolbooks for nature, though, genetics and health factors can help send you to the optometrist’s office. You may as well pick out some cool frames and go back to your reading. If any younger siblings give you trouble, remind them that your parents are likely to invest more in your education (or just hold something way up high where they can’t reach it).


Image: by Brisbane Falling (via Flickr)

Guggenheim JA, Williams C, & UK Biobank Eye and Vision Consortium (2015). Role of Educational Exposure in the Association Between Myopia and Birth Order. JAMA ophthalmology, 1-7 PMID: 26448589

CATEGORIZED UNDER: education, medicine, parenting, top posts
MORE ABOUT: Personal health, Senses
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  • Dan Loeb

    I wonder if it makes a difference whether they were vaginally delivered or delivered via Ceasarean. The first born might suffer more trauma at birth.

  • OWilson

    The stereotypical nerd or librarian holds true.

    The more education, the more reading, the more glasses.

    (I wear glasses, and am a first born) :)

  • Susan Fuller

    It is the nicest way to earn more and more money at home.$40h – $90h…how? part time or full time,I’ve been bringing in $82h… It sounds unbelievable but you wont forgive yourself if you don’t check it out.

    http://www.theladder.cf
    qw

  • Luke101

    I read a book called:” The Birth Order Book”
    It was very interesting and got into all kinds of things that people do.

  • Chip

    It probably has to do with how hard the baby’s head gets squeezed, deforming the eye sockets, on the way out. I wonder if they normalized for birth method.

  • SadButTru

    If we are telling anecdotes, neither of my parents, and/or their parents/siblings had myopia, yet I do have it as the first kid in my family. My brother also has some myopia, but he can do without glasses. All our relatives before us were farmers or were the kind of people who didn’t get much education if any. I am the first one in my family to get higher education. Though, my myopia started when I was 5-6 yo, and I did have a lot of access to outdoors as a kid. So, I would say, this is multifactorial just like all things related to humans/animals.

  • moderatelymoderate

    I’d rather wear glasses than get skin cancer or more wrinkles from spending more time in the sun rather than reading.

  • Sconi grower

    Some scientists are thinking that the eye needs lots of natural sunlight to properly develop the lens. With less sunlight being a result of reading more, that would help explain why genetics matters less than expected.

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Inkfish

Like the wily and many-armed cephalopod, Inkfish reaches into the far corners of science news and brings you back surprises (and the occasional sea creature). The ink is virtual but the research is real.

About Elizabeth Preston

Elizabeth Preston is a science writer whose articles have appeared in publications including Slate, Nautilus, and National Geographic. She's also the former editor of the children's science magazine Muse, where she still writes in the voice of a know-it-all bovine. She lives in Massachusetts. Read more and see her other writing here.

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