The effect of longer-term and exclusive breastfeeding promotion on visual outcome in adolescence

Purpose: Breastfeeding may influence early visual development. We examined whether an intervention to promote increased duration and exclusivity of breastfeeding improves visual outcomes at 16 years of age.
Methods: Follow-up of a cluster-randomized trial in 31 Belarusian maternity hospitals/polyclinics randomized to receive a breastfeeding promotion intervention, or usual care, where 46% vs 3% were exclusively breastfed at 3 months respectively. Low vision in either eye was defined as unaided LogMAR vision of 0.3 or worse (equivalent to Snellen 20/40) and was used as the primary outcome. Open-field autorefraction in a sub-set (N=963) suggested that 90% of those with low vision were myopic. Primary analysis was based on modified intention-to-treat, accounting for clustering within hospitals/clinics. Observational analyses examined other sociodemographic and environmental determinants of low vision.
Results: 13392 (79%) of 17046 participants were followed up at 16 years. Low vision prevalence was 24.2% (95%CI 21.6,26.9%) in the experimental group vs 25.4% (22.9,28.1%) in the control group. Cluster-adjusted odds ratio (OR) of low vision associated with the intervention was 0.95 (95%CI 0.75,1.19); 0.91 (95%CI 0.78,1.06) after adjustment for parental and early life factors. In observational analyses, higher parental education, maternal age at birth (OR 1.13, 95% CI 1.07,1.19/5 year increase), and urban vs rural residence were associated with increased risk of low vision. Number of older siblings was associated with a lower risk; boys had lower risks than girls (0.65, 95%CI 0.60,0.70).
Conclusions: Exclusive breastfeeding promotion had no significant effect on visual outcomes, but other environmental factors showed strong associations.