Around 1 in 3 children and teens around the world is short (near)-sighted, with the global prevalence of myopia set to top 740 million cases by 2050 in this age group, finds a pooled data analysis of the available evidence, published online in the British Journal of Ophthalmology.
Female sex, East Asian or urban area residence, and educational level all seem to be key factors influencing prevalence, the findings indicate.
Short (near)-sightedness (myopia), which describes difficulty seeing objects at a distance, typically starts in early childhood and tends to worsen with age, explain the researchers. It has emerged as a major public health concern, particularly in Southeast Asia, they add.
But the most recent global review of its prevalence only went up to 2015. To obtain a more up to date picture, with a view to informing healthcare policy and preventive efforts, the researchers estimated the current and future prevalence of myopia up to 2050 among 5 to 19 year olds.
They drew on all relevant research and government reports, published up to June 2023. They included a total of 276 studies, involving 5,410,945 children and teens and 1,969,090 cases of myopia, from 50 countries in Asia, Europe, Africa, Oceania, North and Latin America.
They pooled the data from all of these studies, taking account of geographical, temporal, and other variables.
Their analysis revealed a more than tripling in overall prevalence between 1990 and 2023, rising from 24% in 1990-2000 to 25% in 2001-10, followed by much sharper increases to 30% in 2011-19, and 36% in 2020-23, equivalent to around 1 in every 3 children and teens.
While the prevalence among teens surpassed that of children, peaking at 54% during 2020–23, the absolute increase among children from 1990 to 2023 was nearly twice that of teens.
Prevalence was significantly higher in low to middle income countries than in high income countries, and was highest in Japan and lowest in Paraguay between 1990 and 2023.
Certain factors were associated with a higher prevalence, notably residence in East Asia (35%) or in urban areas (29%), female sex (34%), adolescence (47%), and high (secondary) school education (46%).
Based on the figures and trends up to 2023, overall global myopia prevalence is projected to reach around 40% by 2050, exceeding 740 million cases, up from 600 million in 2030, they estimate.
It is expected to be higher among girls and young women than among boys and young men: 33% vs 31% in 2030; 40% vs 35.5% in 2040; and 42% vs 37.5%, respectively, in 2050.
And it is expected to be significantly higher among 13–19 year olds than among 6–12 year olds, with projected rates of 43% vs 21% in 2030, 49% vs 24% in 2040, and 52.5% vs 27.5%, respectively, in 2050.
Low and middle income countries are expected to have a higher prevalence than high income countries, with a projected rate of 41% by 2050. Specifically, Asia is expected to have the highest prevalence of all, with rates of 52% in 2030, 62% in 2040, and 69% in 2050.
The COVID-19 pandemic may have had a role in the sharp increase after 2020, suggest the researchers. "Emerging evidence suggests a potential association between the pandemic and accelerated vision deterioration among young adults," they write.
By way of an explanation for the geographical differences, they suggest that people in East and South Asia have experienced rapid economic development along with the steepest rise in myopia prevalence.
"The elevated incidence of myopia observed in the Asian population, particularly among younger children, as compared with other regions, could potentially account for the observed ethnic disparity," they write.
"Moreover, a correlation between the duration of education and the occurrence of myopia has been observed, suggesting that the early implementation of formal education in certain East Asian nations could potentially serve as a contributing element," they add.
"Conversely, African populations exhibit a lower prevalence of myopia, likely attributed to lower literacy rates and delayed initiation of formal education, typically occurring between the ages of 6 to 8 years for most children," they explain.
Sex differences in prevalence might also 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, they suggest, advocating more physical activity and less screen time for all children and teens.
The researchers acknowledge various limitations to their findings, including the variable quality and considerable differences in the design and methodology of the studies included in their pooled data analysis. The definitions and assessments of myopia also varied widely.
"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 write, adding: "It is crucial to recognise that myopia may become a global health burden in the future."
