Monday March 19 2012
Baby-feeding regimens: it's unclear if they directly affect IQ
“Babies fed on demand do better at school,” reported The Guardian, adding that those who “are fed when they are hungry achieve higher test scores” but that the experience takes its toll on their mothers.
The news is based on what is thought to be the first large-scale study to look at how infant feeding schedules relate to academic achievement later in childhood. After examining how more than 10,000 children were fed at the age of four weeks, the researchers then compared their performances in IQ tests at the age of eight and in school tests up to the age of 14. The researchers were specifically interested in whether feeding babies at set times led to different developmental outcomes compared with feeding on demand. They found that babies fed on demand did better academically later in childhood than schedule-fed babies. However, mothers who fed on demand were more likely to feel that they were not getting enough sleep and felt less confident than mothers who scheduled feeds.
This research suggests that infant feeding patterns are linked to later academic performance, but it does not prove that one causes the other. Although there did appear to be some relationship between the two factors, other considerations such as maternal attitudes and background may explain both. For example, a mother’s attitudes could lie behind both the choice to follow a particular feeding pattern and the way she motivates her child to do well at school. As the researchers themselves have said, these results should be approached cautiously and more research will be required to confirm the findings.
Where did the story come from?
The study was carried out by researchers from the University of Essex and the University of Oxford and was funded by the UK’s Economic and Social Research Council.
The study was published in the peer-reviewed European Journal of Public Health.
This research was covered appropriately in the media, with both The Guardian and the Daily Mail emphasising that the association between feeding patterns and IQ were statistically significant, but may not necessarily have any practical significance in everyday life.
What kind of research was this?
This prospective cohort study examined the association between babies’ feeding schedules and their cognitive development and academic attainment throughout childhood. The study also examined the association between schedule feeding and the mother’s wellbeing. The research included children who were both breastfed and bottle-fed.
This study was “prospective”, which means that the research used initial assessments to establish the babies’ feeding patterns and then monitored how the children’s development progressed in the years that followed. A prospective cohort study is a useful way to examine the relationship between different factors (variables), as it allows researchers to be fairly confident that their measurements are accurate. Collecting information on the babies’ feeding patterns during infancy, as opposed to asking parents to recall them years later, improves the likelihood that this data was accurately estimated.
However, while this study can describe the relationship between these factors, it cannot determine whether feeding patterns directly caused differences in child academic performances. The study authors have themselves urged caution when interpreting the results, as they demonstrate a potential relationship between a mother’s approach to feeding and her child’s level of subsequent educational attainment, but not that one can cause the other.
What did the research involve?
The researchers analysed data from the Avon Longitudinal Study of Parents and Children (ALSPAC), a large ongoing cohort study of children born during the 1990s in and around Bristol in the UK. In all, 14,541 mothers were enrolled in the study while pregnant and they were interviewed repeatedly during their pregnancy and after their child was born. For the current study, the researchers used data collected during these interviews, as well as school attainment test data.
When the babies included in this study were four weeks old, their mothers were asked whether or not they fed their baby on a regular schedule. Based on their responses, the children were classified as being one of the following:
- schedule fed
- attempted schedule fed
- demand fed
Researchers then collected data for several outcomes:
- Maternal wellbeing was measured when the child was between the ages of eight weeks and two years, nine months old (33 months). Measures included sleep sufficiency, maternal confidence, maternal enjoyment and postnatal depression.
- Child cognitive development was measured using IQ scores when the children were eight years old.
- Academic attainment was measured using the Standard Attainment Test (SATs) given to the children at school at ages 5, 7, 11 and 14 years.
The researchers analysed the data while controlling for several variables that may account for, or confound, the relationship between schedule feeding and the outcomes of interest. These variables included the child’s sex, breastfeeding factors (including duration of exclusive breastfeeding), parenting style, maternal health and sociodemographic factors.
What were the basic results?
The researchers found that at four weeks after birth, 7.1% of the mothers reported that they fed to a regular schedule, 23% reported that they tried to feed to schedule and 69.8% reported that they fed on demand.
Mothers who fed to schedule were generally younger and more likely to be single, live in social housing and to be less educated than mothers who fed on demand. They were also likely to report poor health before and during pregnancy. Mothers who fed to schedule were later more likely to report smacking or shouting at their children and less likely to read to them.
The researchers found that babies who were fed to schedule:
- had lower SATs scores than demand-fed children at ages 5, 7, 11 and 14 (p<0.001 at all ages)
- scored 4.3 points lower on IQ tests at age eight (95% CI -5.9 to -2.6, p<0.001)
The researchers then assessed the relationship between feeding pattern and maternal wellbeing. They found that compared with mothers who fed on demand, schedule-feeding mothers:
- were significantly more likely to report getting enough sleep at eight weeks (odds ratio [OR] 1.55, 95% CI 1.31 to 1.84, p>0.001)
- were significantly more likely to report getting enough sleep at eight months (OR 1.62, 95% CI 1.34 to 1.95, p<0.001)
- were significantly less likely to report feeling “sometimes exhausted” at eight weeks (OR 0.52, 95% CI 0.42 to 0.64, p<0.001)
- reported higher levels of maternal confidence and enjoyment at both eight weeks and 33 months (p<0.001 for all measures and time periods)
- had no significant difference in terms of postnatal depression at eight weeks or at 8, 21 or 33 months
How did the researchers interpret the results?
The researchers concluded that feeding infants at regular intervals is associated with better maternal wellbeing but poorer child cognitive development and academic performance.
This large cohort study indicates that infant feeding patterns may be associated with both children’s subsequent academic performance and the wellbeing of their mothers. The researchers emphasised, however, that while the results are statistically significant, they may not reflect “a causal relationship”. In other words, even though there was a statistical link between the two factors, this doesn't prove that the way the children were fed caused them to develop or perform differently.
There is a range of possible explanations that could explain the relationships seen, as the researchers have highlighted. First, they said that the results surrounding maternal wellbeing may reflect a “reverse causality”: that instead of regulated feeding patterns improving a mother’s wellbeing, it may be that mothers who get more sleep and feel more confident are more likely to be able to establish a regular feeding schedule.
The study made statistical adjustments to account for the influence of several different factors, including the children’s social and demographic background. However, other factors such as maternal characteristics may influence the relationship between feeding patterns and academic performance. For example, maternal characteristics could govern both a child’s feeding patterns and development, rather than these factors being directly related to each other.
The researchers say that this is the first large-scale cohort study examining the relationship between feeding to a schedule and academic performance later in childhood. They say that additional research will be needed to confirm the results as well as to examine the mechanisms behind the relationship.
It is also important to remember that this study measured schedule feeding only once, when the infants were four weeks old. It is possible that feeding patterns changed after this time and that children who were classified as schedule fed for this study later became fed on demand. Given this limitation, this study is unable to address the impact of such potential misclassification. The study also failed to look at related factors, such as when the child was weaned onto solid food.
In summary, the study did find a relationship between schedule feeding and academic outcomes later in childhood, but the evidence is not strong enough to influence recommendations on feeding strategies.
Analysis by Bazian