First Born Kids Are More Likely to be Nearsighted, Study Says

First time parents might want to take note.

In most researches about birth order, the first born kids are usually, if not often, the outperformers among siblings. But while the advantages of being the first child in the family cannot be overstated, a new research published Thursday in JAMA Ophthalmology presents an interesting finding that tip the other scale.

The data, as per Live Science, show that first-borns are 10 percent more likely to be near-sighted and 20 percent more likely to have severe myopia, as compared to their siblings. The same report furthers that the chances of being nearsighted or developing myopia is said to be "progressively lower" the younger you are in terms of birth order.

According to TIME, lead author Jeremy Guggenheim, a professor of optometry and vision sciences at Cardiff University's Eye Clinic, and team analyzed data of approximately 90,000 adults ages 40 to 69 from the British Biobank longitudinal survey, combining both demographic and behavioral information. Researchers asked, for instance, how much time the subjects spent outdoors, coupled with their educational information and their "ophthalmological past."

Apart from the younger siblings being less at risk for myopia, Guggenheim and the team also kept on the lookout for other influencing factors. The authors suggest, as per TIME, that a child's education is one reason for his/her nearsightedness, citing previous research that show parents to be investing more in the educational completion of their first kid. With a provision for and access to books, gadgets like iPads, toys, chalkboards, and the like, the child is in a setup conducive to eye strain. Combined with genetics, this then equate to nearsightedness.

"My assumption is that individuals who go on to spend more years in full-time education spend relatively less time outdoors and relatively more time in tasks such as reading during their childhood," Guggenheim said in a statement to TIME.

TIME reports that Guggenheim and co-authors did not expect that the link between birth order and myopia was "educational investment."

"Our original hypothesis was that it would be related to the tendency for first-born children to be a little lighter at birth than average," they said. However the 2013 study Guggenheim referred to is inconclusive, therefore making educational investment a better theory and explanation.

"To be honest, the relationship with birth order interested us because it seemed a little quirky," Guggenheim said. "Scientists are always very careful not to presume causality when they see a correlation, but then again, if a correlation keeps appearing then it must have a cause, even if the cause is indirect."