First-born children run higher risk of becoming nearsighted later in life, compared with their later-born siblings, a study says.
Parents pushing the eldest kid to do better in studies may be partly blamed for the higher myopia risk among the first-borns, the researcher found.
"Our study provides an extra piece of evidence linking education and myopia, consistent with the very high prevalence of myopia in countries with intensive education from an early age," study author Jeremy Guggenheim, of Cardiff University in Britain, was quoted as saying.
For the study, researchers examined birth order and nearsightedness in about 89,000 people, ages 40 to 69, in Britain.
First-borns were 10 percent more likely to be nearsighted and 20 percent more likely to be severely nearsighted than their subsequent siblings, the findings showed, the study said.
Reduced parental investment in education of children with later birth order may be partly responsible, the researchers said.
Education accounted for about 25 percent of the link between birth order and the risk of nearsightedness.
However, in addition to education, there may be other, unmeasured factors that could partially mediate the relationship between birth order and one's risk of nearsightedness, Live Science reported.
The study was published in the journal JAMA Ophthalmology.