Beyond Infant Nutrition: Investigating the Long-Term Neurodevelopmental Impact of Breastfeeding

<b>Background/objectives</b>: Optimal infant nutrition, particularly exclusive breastfeeding for the first 6 months, is crucial for both immediate and long-term health. The early years of life are essential for brain development due of the rapid maturation of social, emotional, cognitive and motor capacities. While benefits of breastfeeding are well established, its long-term impact on neurodevelopment remains underexplored. This study investigates the relationship between breastfeeding duration and neurodevelopment outcomes at 5 years of age. <b>Methods</b>: This prospective cohort study followed 92 term-born infants in Varna, Bulgaria (2017-2024). Parents provided informed consent and completed questionnaires regarding demographic characteristics, feeding practices and atopic diseases. At 5 years of age, children were assessed using the Neurodevelopmental Test for Five-Year-Olds. <b>Results</b>: Feeding practices differed significantly across groups (<i>p</i> < 0.001), with exclusive breastfeeding more prevalent among children breastfed for longer. At 5 years, significant differences were observed in language development (<i>p</i> = 0.037) and behavioral outcomes (<i>p</i> = 0.001). A linear regression model for behavioral outcomes (F = 2.29, <i>p</i> = 0.011, R² = 0.297) showed that breastfeeding for 6-12 months was associated with more favorable behavior (Estimate = -5.88, <i>p</i> = 0.026), compared to less than 6 months. In contrast, paternal secondary education (Estimate = 3.58, <i>p</i> = 0.048) compared to higher education and mixed ethnicity (Estimate = 12.55, <i>p</i> = 0.023) compared with Bulgarian ethnicity were associated with poorer behavioral outcomes (Estimate = 3.58, <i>p</i> = 0.048). <b>Conclusions</b>: Breastfeeding for 6 to 12 months may be associated with improved behavioral development, and to a lesser extent, language outcomes at age five. However, these domain-specific associations were not consistently supported across all statistical methods and should be interpreted with caution. Neurodevelopment is influenced by a complex interplay of nutritional, social and environmental factors. Longitudinal studies are needed to clarify the long-term effects of breastfeeding duration on neurodevelopment.