Global variations and time trends in the prevalence of childhood myopia: a systematic review and meta-analysis

Abstract

BackgroundEthnic and geographical differences in prevalence of childhood myopia seem to have changed over time. We aimed to quantify the variation in prevalence of childhood myopia over time, accounting for demographic and study design factors. MethodsPopulation-based surveys of myopia prevalence published in English were identified from a combination of text words for myopia (short$sight*/myopi?/myope$/refractive error$/ocular refraction), childhood (child/childhood/children/adolescent/adolescence/teenage), epidemiology (incident/incidence/prevalen*/population$/survey$) combined with the related subject headings in Medline (from Jan 1, 1950, to Feb 16, 2015), Embase (Jan 1, 1980, to Feb 16, 2015), and Web of Science (Jan 1, 1970, to Feb 16, 2015). Bayesian multilevel binomial logistic regression analyses of log-odds of myopia provided mutually adjusted associations for age, ethnicity, sex, urban versus rural setting, survey year, and study design factors. Findings143 articles (374 349 participants aged 6 months to 18 years, 74 847 cases of myopia) reported age-specific prevalence of childhood myopia in 42 countries representing nine ethnic groups between 1958 and 2014. Increase in myopia prevalence with age varied by ethnicity. East Asians showed the highest prevalence at all ages, reaching 69% (95% credible interval [CrI] 61–77) at 15 years of age (86% [79–91] among Singaporean-Chinese). In Africa, blacks had the lowest prevalence (5·5% at 15 years [3·1–9·0]). Whites had the highest prevalence at 15 years (16·7%, 10·6–24·5). Time trends in myopia prevalence were stable in whites, and increased by 23% per decade in East Asians (odds ratio 1·23, 95% CrI 1·00–1·55), with no clear evidence of time trends in other ethnic groups. In all ethnic groups, children from urban environments were more than twice as likely to be myopic as those from rural environments (2·61, 1·79–3·86). In whites and East Asians, sex differences emerged at about 9 years of age; by late adolescence girls were twice as likely as boys to be myopic. InterpretationMarked ethnic differences in age-specific prevalence of myopia exist, with significant increases in prevalence over time in East Asians. An urban environment seems to be universally associated with a high risk of myopia. Findings suggest that environmental factors have an important role in explaining ethnic variations in myopia prevalence and differences in time trends. FundingBUPA foundation.