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Breastfeeding during infancy and neurocognitive function in adolescence: 16-year follow-up of the PROBIT
Seungmi Yang1, Richard M Martin2,3, Emily Oken4
1Department of Epidemiology, Biostatistics and Occupational Health, Faculty of Medicine, McGill University, Montreal, Quebec, Canada.
Insights
A breastfeeding promotion intervention showed no long-term neurocognitive benefits in adolescents. However, a slight improvement in verbal function was observed, consistent with earlier findings but with a smaller effect size.
Area of Science:
- Child Development
- Public Health Interventions
- Neuroscience
Background:
- Long-term neurocognitive effects of breastfeeding are primarily based on observational studies.
- This study investigates the lasting impact of a breastfeeding promotion intervention on neurocognitive development.
- Previous research indicated early school-age benefits from the intervention.
Purpose of the Study:
- To evaluate the persistence of neurocognitive benefits from a breastfeeding promotion intervention at age 16.
- To assess the long-term effects of promoting prolonged and exclusive breastfeeding on cognitive function in adolescents.
Main Methods:
- A 16-year follow-up of the cluster-randomized Promotion of Breastfeeding Intervention Trial (PROBIT) involving 13,557 participants.
- Neurocognitive function assessed using a computerized test battery across 7 domains in 13,427 adolescents.
- Intention-to-treat (ITT) and instrumental variable (IV) analyses were employed to evaluate intervention effects and causal impacts of breastfeeding duration.
Main Results:
- No statistically significant differences in overall neurocognitive scores between intervention and control groups in ITT analyses.
- Slightly higher scores in verbal function (1.4 points) and memory (1.2 points) in the intervention group after adjusting for baseline characteristics.
- IV analysis indicated a significant positive effect of exclusive breastfeeding for ≥3 months on verbal function (3.5 points), but no effects on other domains.
Conclusions:
- The breastfeeding promotion intervention did not yield significant long-term benefits for overall adolescent neurocognitive function.
- A modest, persistent benefit was observed specifically for verbal function, though the effect size diminished by adolescence.
- Findings highlight the complexity of long-term intervention effects and the need for further research into causal mechanisms.
Background:
Evidence on the long-term effect of breastfeeding on neurocognitive development is based almost exclusively on observational studies. In the 16-year follow-up study of a large, cluster-randomized trial of a breastfeeding promotion intervention, we evaluated the long-term persistence of the neurocognitive benefits of the breastfeeding promotion intervention previously observed at early school age.
Methods And Findings:
A total of 13,557 participants (79.5% of the 17,046 randomized) of the Promotion of Breastfeeding Intervention Trial (PROBIT) were followed up at age 16 from September 2012 to July 2015. At the follow-up, neurocognitive function was assessed in 7 verbal and nonverbal cognitive domains using a computerized, self-administered test battery among 13,427 participants. Using an intention-to-treat (ITT) analysis as our prespecified primary analysis, we estimated cluster- and baseline characteristic-adjusted mean differences between the intervention (prolonged and exclusive breastfeeding promotion modelled on the Baby-Friendly Hospital Initiative) and control (usual care) groups in 7 cognitive domains and a global cognitive score. In our prespecified secondary analysis, we estimated mean differences by instrumental variable (IV) analysis to account for noncompliance with the randomly assigned intervention and estimate causal effects of breastfeeding. The 16-year follow-up rates were similar in the intervention (79.7%) and control groups (79.3%), and baseline characteristics were comparable between the two. In the cluster-adjusted ITT analyses, children in the intervention group did not show statistically significant differences in the scores from children in the control group. Prespecified additional adjustment for baseline characteristics improved statistical precision and resulted in slightly higher scores among children in the intervention for verbal function (1.4 [95% CI 0.3-2.5]) and memory (1.2 [95% CI 0.01-2.4]). IV analysis showed that children who were exclusively breastfed for ≥3 (versus <3) months had a 3.5-point (95% CI 0.9-6.1) higher verbal function, but no differences were observed in other domains. While our computerized, self-administered cognitive testing reduced the cluster-level variability in the scores, it may have increased individual-level measurement errors in adolescents.
Conclusions:
We observed no benefit of a breastfeeding promotion intervention on overall neurocognitive function. The only beneficial effect was on verbal function at age 16. The higher verbal ability is consistent with results observed at early school age; however, the effect size was substantially smaller in adolescence.
Probit Trial Registration:
ClinicalTrials.gov NCT01561612.
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