This secondary analysis of a prospective cohort study demonstrates that when appropriately grown, congenitally normal, term babies are breastfed beyond one month of age they have significantly greater scores in cognitive assessment with no difference in behavioural assessment.
The findings of this study are consistent with existing evidence, demonstrating a positive impact of breastfeeding on neurocognitive function [21, 24, 25, 28, 32]. Our study supports this further by separating the areas for assessment into verbal, non-verbal, spatial and standard, facilitating a more thorough assessment of each area of neurocognition. When looking at these in more detail we can see significantly greater scores between groups in relation to assessments of GCA which led to an overall difference in the collective ultimate GCA score. This suggests a more optimal ability to perform complex transformations of information and is a combination of verbal, non-verbal reasoning and spatial skills . In relation to the BAS II assessment, while spelling and reading scores were greater in the breastfed group, there was no significant difference in relation to numerical assessment. This contradicts existing evidence assessing mathematical ability in breastfed children  and hence should be interpreted with caution. The CBLC (behavioural assessments) in this study showed no difference between groups. This has been reproduced in other studies with variable findings. Some studies have reported improved behavioural scores when also using the CBLC in breastfed children, and one in particular used a diagnosis of ADHD as a marker of behavioural difficulties and demonstrated that this is less likely in those who are breastfed [42, 43, 44].
As expected, mothers in the breastfeeding group had a greater maternal age and lower Townsend score (degree of social deprivation) the latter being taken into consideration as part of the adjusted analysis [22 ,23, 24, 25 ,31]. A previous systematic review looked at the effect of confounders and its impact on the results of breastfeeding and neurocognitive scores . Many previous studies have not controlled for confounders as thoroughly as this study and therefore may have contributed to skewed results .
BAS II is not an assessment tool that has been used to examine neurocognitive function in relation to breastfeeding previously. This test gives a General Conceptual Ability to give the overall abilities of the child, not just based upon IQ. Scales such as BAS II are key to ensuring full assessment of children beyond IQ to assess for executive functioning, attention, processing and memory and thus facilitate selection for further assessment for dyslexia, autistic spectrum disorder and attention-deficit/hyperactivity disorder [26, 30]. A review into the BAS II edition demonstrated its ability through psychometric assessments to contribute to a ‘holistic analysis of the child’s functioning’ . Hence, our study evaluates the effect of breastfeeding on the child’s neurocognitive development as a whole and not just on an intellectual level. CBLC has been studied before and a systematic review reflects studies that have demonstrated that children who have been breastfed for at least three or four months may have behaviour and conduct scores using this system. These same studies indicated that a longer time period of breastfeeding seems to be more important than the initiation itself .
Strengths of the study include its prospective nature and robust methodology. The study is novel in that it is, to our knowledge one of the longest follow-up in specifically appropriately grown, term, breastfed children published to date, as well as being one of the first to use the aforementioned scales for assessment in relation to breastfeeding and neurocognition. Study limitations include the reliability upon maternal retrospective recall of breastfeeding status and duration as well as lack of information regarding breast-feeding exclusivity. However, existing evidence suggests that such maternal recall is a reliable and valid method of assessment, although its’s application up to 12-years has not been formally assessed .
Existing evidence demonstrates more optimal myelination and cerebral cortex maturation in the brains of breastfed versus those who are not [9,39]. The nutritional elements that are linked to these differences include lutein, long chain fatty acids, sphingolipid and a- tocopherol [7, 8, 9, 10]. Carotenoids such as lutein and zeaxanthin have been found to be one of the few nutrients present in breastmilk yet only in trace amounts in formula and are vital in the development of the nervous system and vision . Lutein is selectively deposited in the brain promoting corpus callosum and cerebral cortical gray matter maturation . This has been demonstrated on brain imaging by MRI (Magnetic Resonance Imaging) and correlates with the shown significant differences seen in the white and subcortical gray matter when comparing breast fed and non-breastfed children . The corpus callosum is responsible for cognitive processing, motor function and helps with the transfer of visual, auditory and somatosensory information to the temporal, occipital and parietal lobes of the brain . Some studies have shown that formula that has been supplemented with long chain fatty acids can produce a similar improvement in children’s cognitive abilities . This could be extrapolated to indicate that certain nutritional elements of breastmilk could be the cause of improved neurocognitive scores and therefore further studies into this and addition to formulas could replicate these findings.
The findings of our study provide a further incentive for mothers to breastfeed. At the time of this study, breastfeeding rates among mothers in Northern Ireland were some of the lowest in the UK at 36% . Reasons for this may have included poor initiation prior to discharge, lack of education and cultural differences . Since the subsequent implementation of the first Northern Ireland regional breastfeeding strategy and the more recent ‘Ten Year Breastfeeding Strategy’, rates have significantly improved due to improved hospital and community training and service provision and therefore maternal education and support [20, 35, 36, 37, 38]. Providing education antenatally and maternal support in relation to breastfeeding has been shown to improve uptake . NICE (National Institute for Health and Care Excellence) encourage this uptake through the fostering of training, education and support as a key part of postnatal care for all mothers .
While the findings of this study support breastfeeding, due to the nature of the scoring systems and the influence of an abundance of confounding variables, particularly as children get older, one cannot directly imply that that breastfed children are more intelligent but simply objectively interpret the findings in relation to existing evidence. Further studies at this age considering the interaction of additional confounders must be performed to support this.