Firstborn Kids More Likely to Be Nearsighted

A new study finds firstborn children are more likely to develop nearsightedness. REUTERS/Lucy Nicholson

Myopia, or nearsightedness, is a common vision problem that affects as much as 30 percent of the U.S. population. Researchers have identified a number of factors that may figure into why a person's ability to see distances may deteriorate early in life. Part of the reason is certainly your DNA, though researchers have found genetic inheritance accounts for only a small number of people with myopia. The work of the modern world, where we all stare at computer screens hours each day, could also explain rising rates of nearsightedness. And now a new study finds birth order may also play a role in vision problems.

The study, published Thursday in JAMA Ophthalmology, looked at data from the UK Biobank, an initiative to track health and disease trends in the country, which was started by the government in partnership with a number of medical institutions. All subjects were white, between the ages of 40 and 69, and had vision assessments with no history of eye disorders. After adjusting for factors such as age and gender, the researchers found firstborn individuals were about 10 percent more likely to be nearsighted. They were also about 20 percent more likely to have severe distance vision problems than later-born individuals.

The authors suggested that nearsightedness may be more common among firstborn children due to the overzealous efforts of parents to encourage academic achievement and learning. This could mean eldest children end up doing activities that predisposes them to myopia—spending more time inside and on the computer, for example (other recent research has found children who are outdoors more often have better distance vision). By the time a second or third child comes around, parents may become a little more lax about academically enriching but eye-straining activities.

To test their hypothesis, the researchers then adjusted their data for "education exposure"—specifically, whether the individual had received a full-time education and their highest degree earned. After that, the researchers observed the association between birth order and myopia decreased by approximately 25 percent.

"These results add to the extensive literature implicating a role for education in the etiology of myopia," the researchers wrote in the study. "Although a causal relationship cannot be confirmed using observational data."