The associations between near visual activity and incident myopia in children: A nationwide 4-year follow-up study

Objective
This nationwide population-based study aimed to examine the prospective association between near visual activities and incident myopia in Taiwanese children 7 to 12 years old over a 4-year follow-up period.
Design
Prospective cohort design.
Participants
There were 1958 children aged 7 to 12 years from the Taiwan 2009 National Health Interview Survey who were linked to the 2009 through 2013 claims data from the National Health Insurance system.
Methods
Multivariable Cox proportional hazard models were used to estimate the associations between 3 types of near visual activities in sedentary posture, namely reading (< 0.5, 0.5-0.9, ≥1.0 hours per day [h/d]), use of computer, Internet, and games (<0.5, 0.5-0.9, ≥1.0 h/d), and “cram school” attendance (<0.5, 0.5-1.9, ≥2.0 h/d), and incident myopia.
Main Outcome Measures
Prevalent myopia was defined as those who had ≥2 ambulatory care claims (International Classification of Diseases code 367.1) in 2008-2009. Incident myopia was defined by those who had at least 2 ambulatory care claims (International Classification of Diseases code 367.1) during the 4-year follow-up period (2010-2013) after excluding prevalent cases.
Results
Overall, 26.8% of children had myopia at baseline, and 27.7% of those without myopia at baseline developed incident myopia between 2010 and 2013. On average, they spent 0.68±0.86 h/d on computer/Internet use, 0.63±0.67 h/d on reading, and 2.78±3.53 h/d on cram school. The results showed that children attending cram schools ≥2 h/d (hazard ratio, 1.31; 95% confidence interval, 1.03-1.68) had a higher risk of incident myopia. The effects of these activities remained similar in sensitivity analyses.
Conclusions
Cram school attendance for ≥2 h/d may increase the risk of children’s incident myopia. This effect may be due to increased near visual activity or reduced time outdoors.