Myopia and Childhood Migration: A Study of 607 862 Adolescents

Abstract

Purpose: Immigration studies can shed light on myopia development and reveal high-risk populations. To this end, we investigated the association among immigration, age at immigration, and myopia occurrence during adolescence.

Design: Population-based, retrospective, cross-sectional study.

Participants: Six hundred seven thousand eight hundred sixty-two adolescents, Israeli born and immigrants, with origins in the former Union of Soviet Socialist Republics (USSR), Ethiopia, or Israel, assessed for medical fitness for mandatory military service at 17 years of age between 1993 and 2016.

Methods: Myopia and high myopia were defined based on right eye refractive data. Age at immigration was categorized into 0 to 5 years of age, 6 to 11 years of age, and 12 to 19 years of age. Univariate and multivariate logistic regression models were created. Myopia odds ratios (ORs) were calculated according to immigration status, with Israeli-born natives as controls. Next, myopia ORs were calculated according to age at immigration, with Israeli-born of same origin as controls.

Main outcome measures: Myopia prevalence and ORs.

Results: Myopia was less prevalent among immigrants than Israeli-born controls. When stratified according to age at immigration, a decrease in myopia prevalence and ORs with increasing age at migration were observed, most prominent in immigrants arriving after 11 years of age, who also showed lower high-myopia ORs. The immigrants from the USSR and Ethiopia arriving after 11 years of age showed a myopia OR of 0.65 (95% confidence interval [CI], 0.63-0.67; P < 10^-205) and 0.52 (95% CI, 0.46-0.58; P < 10^-27) compared with the Israeli-born controls. Notably, Ethiopians arriving earlier than 5 years of age showed a 2-fold higher myopia OR than those migrating after 11 years of age.

Conclusions: Immigrants arriving after 11 years of age showed markedly lower ORs for myopia and high myopia relative to Israeli-born controls or those arriving during early childhood, likely because of environmental and lifestyle changes. Differences between immigrants arriving up to 5 years of age and those arriving between 6 and 11 years of age were relatively smaller, suggesting exposures at elementary school age play a greater role in this population.