Patterns of myopigenic activities with age, gender and ethnicity in Sydney schoolchildren

Purpose To examine the patterns of myopigenic activity (high near work, low time outdoors) in children growing up in Sydney, Australia, by age, ethnicity and gender. Methods The Sydney Adolescent Vascular and Eye Study (SAVES) re-examined children from the two age cohorts (6 and 12years at baseline) from the Sydney Myopia Study (SMS). At 56year follow-up, 863 in the younger cohort and 1196 in the older cohort had complete refraction data. Cycloplegic autorefraction (cyclopentolate 1%; Canon RK-F1) was measured at baseline and follow-up. Children who became myopic (0.50dioptres spherical equivalent refraction) were those classified as non-myopic at baseline and myopic at follow-up. A detailed questionnaire was administered to measure weekly activities, including time spent outdoors and near work at both baseline and follow-up examination. Results Overall, 128 (14.8%) children in the younger cohort and 210 (17.6%) in the older cohort became myopic. At follow-up, for both cohorts, children had significantly reduced the amount of time spent outdoors (younger cohort, p=0.001, older cohort, p<0.0001) and increased near work time (younger cohort, p<0.0001, older cohort, p=0.006). Children of East Asian ethnicity spent significantly less time outdoors by more than 7h per week (both cohorts at baseline and follow-up, all p<0.0001) and more time in near work activities by close to 3h compared to European Caucasian children at all ages examined (both cohorts at baseline and follow-up all, p<0.03). The average pattern of activity for girls differed from that of boys in a similar way (both cohorts at baseline and follow-up all, p<0.0001). The two independent samples of 12year-old children provided by follow-up in the younger cohort and baseline in the older cohort gave very similar answers to the questionnaire, with significant differences only evident for computer use (p=0.001) and books read (p<0.0001). Conclusions Answers to the activity questionnaire were very similar in the two cohorts of 12year-olds, suggesting that the questionnaire gives reproducible answers. However, further work is required for validation. Children's pattern of activities become more myopigenic with age, and differed by gender and by ethnicity at all ages, with girls having a more myopigenic activity pattern than boys, and children of East Asian ancestry having a more myopigenic activity pattern than European Caucasian children.