I am a first-born child. I am also extremely nearsighted. I always thought of these facts as unrelated, but recent research suggests otherwise.
Over the past few years, researchers have produced tentative evidence that myopia is related to birth order. Now, a large-scale study from the United Kingdom confirms that being the first born of your family significantly increases the odds you will be nearsighted.
You read that right. No need to adjust your glasses.
The paper, just published in the journal JAMA Ophthalmology, shows this is not a new phenomenon. The study also points to a partial explanation for this puzzling discovery.
First-born kids feel more parental pressure to achieve, which leads them to spend more time reading and studying, and subsequently increases their odds of becoming nearsighted.
A research team led by Cardiff University's Jeremy Guggenheim examined data on 89,120 British adults gathered between 2006 and 2010. It included detailed demographic information, including the level of education achieved. Participants ranged in age from 37 to 73, making them considerably older than the teens and pre-teens surveyed in previous research on this topic.
"First-born individuals were approximately 10 percent more likely to have myopia, and approximately 20 percent more likely to have high myopia, than later-born individuals," the researchers conclude. "Therefore, the association between birth order and myopia is not owing to a new environmental pressure in the last 30 to 40 years."
That association was significantly weakened when the researchers adjusted for two measures of education: The participants' achievement level (as measured by the diploma or certificate they earned), and the age at which they stopped going to school full-time.
This suggests a possible mechanism driving this dynamic: The fact that first-born children tend to spend more time studying, and less time outdoors, than their younger siblings. As the researchers note, previous studies have found that "children with an earlier birth order do relatively better at school, owing to parents investing more time, effort, and/or resources in educating" them.
That explanation is also consistent with the results of a separate study published earlier this year. It found attending an "academically selective school" increased the odds of nearsightedness in a sample of 12- and 13-year-olds in Northern Ireland.
So first-born kids feel more parental pressure to achieve, which leads them to spend more time reading and studying, and subsequently increases their odds of becoming nearsighted. That dynamic accounts, in part, for these findings; other factors remain (forgive me) blurry.
As Guggenheim and his colleagues note, this is not just an interesting bit of trivia: It's also a public health issue. Myopia, they note, "is a cause of visual impairment and blindness, either directly or indirectly through a predisposition to cataract, glaucoma, and retinal detachment."
Given those down-the-road consequences, parents might want to make sure their children—especially that achievement-oriented first-born daughter or son—balance their reading and computer work with abundant time outdoors.
This will be an important issue to explore in the future, given that so many of today's children spend an enormous amount of time staring at small screens—regardless of their birth order or interest in education.
Does this mean we're producing a nearsighted generation? If so, we'll have to somehow acknowledge the likely cause of our mass myopia. Perhaps we will refer to our spectacles as "Google glasses."
Findings is a daily column by Pacific Standard staff writer Tom Jacobs, who scours the psychological-research journals to discover new insights into human behavior, ranging from the origins of our political beliefs to the cultivation of creativity.