Summarize a research paper

Aim To test whether adding a daily 40 minute outdoor recess reduces myopia incidence over two school years in children aged 7–9. Methods Cluster randomised trial in 24 primary schools in Taipei and Kaohsiung (Sept 2021–June 2023); 1,847 children. Schools pair matched on baseline myopia prevalence: 12 intervention schools (n=931) with a supervised 40 min outdoor recess, 12 controls (n=916) with the standard 15 min recess. Cycloplegic refraction at baseline, 12, and 24 months by blinded optometrists; axial length measured by partial coherence interferometry; parental questionnaires on near work, parental myopia, and outdoor time. Mixed effects models clustered at school level; 213 children (11.5%) lost to follow up. Key findings Cumulative myopia incidence: 15.4% (intervention) vs 21.9% (control); adjusted OR 0.64 (95% CI 0.48–0.85). Mean axial elongation: 0.31 mm vs 0.38 mm (p=0.003). Larger effects in children with two myopic parents. Typhoon related closures (~6 weeks total) reduced outdoor time; only 71% of scheduled sessions occurred. No serious adverse events. Limitations Moderate ICC in the cluster design; seasonal light variation not measured with personal dosimeters; differential loss to follow up (9.8% intervention vs 13.3% control). Why it matters A simple, low cost change to the school day may meaningfully reduce new myopia in children, though longer trials with objective light monitoring are needed.