Risk factors for rapid axial length growth in a prospective cohort study of 3-year to 9-year-old Chinese children

To identify factors contributing to rapid axial length (AL) growth in children aged 3-9 years. Four thousand four hundred thirty-five children were followed from 2019 to 2022. AL and corneal curvature were measured using an IOLMaster 500, while refractometry and visual acuity were also assessed. Baseline data included demographics and parental myopia status, with annual updates on height, weight and behavioural factors. Latent class growth model was used to discover AL trajectories, whereas multiple logistic regression was used to identify determinants of rapid AL elongation. For all participants, baseline age and parental myopia influenced AL growth. Specifically, children aged 3-6 years exhibited faster AL elongation when engaging in persistent excessive homework time (OR, 2.86, 95% CI 1.31 to 6.95) and near-work activities (OR, 2.13, 95% CI 1.12 to 4.10). For the 7-9-year group, the risk factors of rapid AL growth included being female (OR, 2.05, 95% CI 1.45 to 2.90) and need myopia correction at baseline (OR, 3.19, 95% CI 2.02 to 5.02). Notably, actively engaging in outdoor activities had a protective effect in the 7-9-year group (OR, 0.65, 95% CI 0.43 to 0.97). This study delineates AL growth trajectories in children aged 3-9 years and highlights distinct risk factors for rapid AL growth. These findings underscore the necessity of implementing age-specific strategies for myopia prevention and control.