Effect of Education on Myopia: Evidence from the United Kingdom ROSLA 1972 Reform

Abstract

Purpose: Cross-sectional and longitudinal studies have consistently reported an association between education and myopia. However, conventional observational studies are at risk of bias due to confounding by factors such as socioeconomic position and parental educational attainment. The current study aimed to estimate the causal effect of education on refractive error using regression discontinuity analysis.

Methods: Regression discontinuity analysis was applied to assess the influence on refractive error of the raising of the school leaving age (ROSLA) from 15 to 16 years introduced in England and Wales in 1972. For comparison, a conventional ordinary least squares (OLS) analysis was performed. The analysis sample comprised 21,548 UK Biobank participants born in a nine-year interval centered on September 1957, the date of birth of those first affected by ROSLA.

Results: In OLS analysis, the ROSLA 1972 reform was associated with a -0.29 D (95% confidence interval [CI]: -0.36 to -0.21, P < 0.001) more negative refractive error. In other words, the refractive error of the study sample became more negative by -0.29 D during the transition from a minimum school leaving age of 15 to 16 years of age. Regression discontinuity analysis estimated the causal effect of the ROSLA 1972 reform on refractive error as -0.77 D (95% CI: -1.53 to -0.02, P = 0.04).

Conclusions: Additional compulsory schooling due to the ROSLA 1972 reform was associated with a more negative refractive error, providing additional support for a causal relationship between education and myopia.

Figure 1.

Flow diagram illustrating the selection of UK Biobank participants for the regression discontinuity analysis.

Figure 2.

The association of the ROSLA 1972 education reform with the proportion of participants reporting completion of full-time education at age 15 years or younger. Points represent the mean for each forthcoming year of birth (running from September to September). The vertical dotted line represents the September 1957 cutoff date denoting the month and year of birth for those first affected by ROSLA 1972. Individual outcomes are grouped in three-month bins.

Figure 3.

Discontinuity in age completing full time education for participants stratified by highest educational qualification. Triangles represent participants born before the cutoff date; circles represent participants born after the cutoff date. Individual outcomes are grouped in three-month bins. Solid black lines represent the lines of best fit from the linear regression of educational attainment on the running variable.

Figure 4.

Effect estimate of the ROSLA 1972 education reform on refractive error obtained using regression discontinuity analysis and OLS regression. Results are presented for the full sample or separately for those with a high genetic predisposition (High PRS) or a low genetic predisposition (Low PRS) of myopia based on a binary polygenic risk score.

Figure 5.

Causal effect estimates of the ROSLA 1972 educational reform obtained using regression discontinuity analysis for different bin sizes at a range of different bandwidths.