Physical activity and myopia in Danish children—The CHAMPS Eye Study

Purpose To determine associations between physical activity (PA) and myopia in Danish school children and investigate the prevalence of myopia. Methods This is a prospective study with longitudinal data on PA in a Danish child cohort. Physical activity (PA) was measured objectively by repeated ActiGraph accelerometer measurement four times with different intervals (1–2.5 years) at the mean ages 9.7, 11.0, 12.9 and 15.4 years. Mean intensity of PA was estimated as counts/minutes, and time spent in sedentary, light, moderate and vigorous PA was summed using defined cut-off points. The ophthalmologic examination was conducted at the mean age of 15.4 ± 0.7 years and included cycloplegic autorefraction and biometry. Results A total of 307 children participated in the Childhood Health, Activity, and Motor Performance School (CHAMPS) Eye Study. The cycloplegic spherical equivalent (SE) was 0.30 ± 1.46 dioptres. The prevalence of myopia was 17.9% (SE ≤−0.5 dioptres). Mean axial length (AL) was 23.5 ± 0.9 mm. For all participants, the overall mean daily distribution of PA was 67.2% in sedentary, 25.6% in light, 4.4% in moderate and 2.9% in vigorous PA. Age- and sex-adjusted linear regression showed no association between PA and SE or AL. In a prospective slope analysis, there was no association between accumulated PA during the 7 years and AL or SE. Conclusion The prevalence of myopia among Danish children was 17.9%. By logistic regression and slope analysis, we found no association between PA and myopia, in this first of its kind study based on objective and repeated PA data.