Why your first-born kid is more likely to be nearsighted

During the said study, researchers checked nearsightedness records and birth order of around 89,000 individuals aged between 40 and 69 years.

To make sure that there wasn’t something about having lots of kids that could affect eyesight, Guggenheim and his colleagues compared families with two children to the entire database, and found the relationship between myopia, firstborns and later siblings to be pretty much the same.

Myopia-the scientific term for nearsightedness-is a growing concern in fast-developing countries like India and China, where rates of childhood nearsightedness have skyrocketed in the past couple of generations. “Because the condition is a cause of visual impairment and blindness, it is becoming an increasingly important public health issue”.

Several factors were combined for the analysis, such as behavioral data – like the amount of time the participants spent outdoors -, demographic information, ophthalmologic past, and educational history. Another recent study has shown that most parents are more likely to invest into the educational development of their firstborn child than in that of their second and third children. Moreover, first-borns were 20 percent more likely to acquire high myopia- a more severe form.

Again, there is no empirical evidence that directly links firstborns to myopia, but we can’t deny the fact that the incidence of such an affliction increases given both the genetic background and the parent’s approach to his education.

Firstborn children are 10 percent more likely to be nearsighted than latter-borns, according to a study published Thursday in JAMA Ophthalmology.

Guggenheim explains that is a natural instinct from parents to provide the best education for their first child.

“In the current study we set out to test whether the link between birth order and myopia might have arisen because first-born individuals tend to spend slightly longer in full-time education than later-born individuals”, Jeremy Guggenheim, the lead author, told NPR.

The report suggests that spending more time outdoors reduces nearsightedness rates. So, the education of children with later birth order gets less intense.

Guggenheim and his team at first did not think the connection between birth order and myopia was related to 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”.