More than one in three children and teenagers worldwide are shortsighted, according to the largest study of its kind, prompting calls to discourage screen time and increase physical activity.
Shortsightedness, or myopia, is an eye condition where someone cannot see objects far away clearly. It is usually corrected with glasses or contact lenses.
Experts are unsure why it occurs but studies have shown that children who use computers or smart devices for long periods are at greater risk. Some say that spending more time outdoors can help.
The most comprehensive global analysis to date reveals a dramatic increase in myopia over the last30 years, with the toll of myopia among children and teenagers set to top 740m cases by 2050.
Girls, and children or teenagers living in urban areas, are more likely to develop the condition, according to the analysis published in the British Journal of Ophthalmology.
Myopia typically starts in early childhood and tends to worsen with age, according to the researchers led by Sun Yat-sen University in Guangzhou, China. The condition has emerged as a major public health concern, they added.
The most recent global review of its prevalence went up to 2015. To obtain a more up to date picture, to inform healthcare policy and preventive efforts, the researchers estimated the current and future prevalence of myopia up to 2050 among people aged between five and 19.
They drew on all relevant research and government reports published to June 2023. They included a total of 276 studies, involving more than five million children and teenagers and almost 2m cases of myopia from 50 countries in Europe, North and South America, Asia, Africa and Oceania.
The data was then pooled from all the studies, accounting for geographical and other variables.
The analysis revealed a rise in prevalence from 24% in 1990-2000 to 25% in 2001-10, followed by sharper increases to 30% in 2011-19, and 36% in 2020-23.
Based on the figures and trends up to 2023, global myopia prevalence is projected to reach about 40% by 2050, exceeding 740m cases, up from 600m in 2030, the researchers estimated.
It is expected to be higher among girls and young women than boys and young men, and higher among 13 to 19-year-olds than among six to 12-year-olds.
The Covid pandemic may have played a role in the sharp increase after 2020, the researchers said. “Emerging evidence suggests a potential association between the pandemic and accelerated vision deterioration among young adults,” they wrote.
Sex differences in prevalence might be explained by the fact that girls reach puberty faster than boys and tend to spend less time outdoors and more time on close-range activities, the researchers suggested. They called for more physical activity and less screen time for all children and teenagers.
The researchers acknowledged limitations to their findings, including differences in the design and methodology of the studies included in their pooled data analysis.
“Despite these known limitations, given the large sample size included, our estimates of the prevalence of myopia are considered to be close to the precise number,” they wrote, adding: “It is crucial to recognise that myopia may become a global health burden in the future.”