Breastfed babies 'upwardly mobile' study claims

Tuesday June 25 2013

“Breastfeeding babies improves their chance of climbing the social ladder,” reports The Independent.

Previous research has linked breastfeeding to a number of health benefits for the baby, including improved brain function and reduced vulnerability to infection.

But can breastfeeding your child really have any lasting benefit? A recent study suggests it can.

The UK study looked at the influence of breastfeeding on social mobility. In this paper social mobility was measured by comparing the jobs fathers had with the jobs children grew up to have.

The researchers tracked groups of people – children born in 1958 and children born in 1970. Breastfeeding status was reported by mothers and then around 30 years later social class – as defined by their job – was assessed. Cognitive and stress tests were also carried out around the ages of 10-11.

They found that in both groups, breastfeeding was associated with an increased likelihood of being upwardly mobile (having a better job than your father) and a corresponding decreased likelihood of being downwardly mobile (having a worse job than your father) compared to people who were not breastfed.

Breastfed children also scored better on the cognitive and stress tests, which could possibly explain the results.

While this type of study design can never prove a direct cause and effect, there is a wide range of other evidence about the other benefits of breastfeeding. All women who can safely breastfeed their child are recommended to do so. 

Where did the story come from?

The study was carried out by researchers from University College London and the University of Essex. It was funded by the UK Economic and Social Research Council, the International Centre for Lifecourse Studies in Society and Health, and the Research Centre on Micro-Social Change.

The study was published in the peer-reviewed journal, Archives of Disease in Childhood. This article is open-access and is available free from the publisher’s website.

What kind of research was this?

This was an analysis of two cohort studies, one which had followed a group of people who had been born in Britain during one week in 1958, and the other during 1970. It aimed to determine whether there was a link between being breastfed and social mobility.

The story was well reported by both the Mail Online and The Independent.

What did the research involve?

The researchers followed 17,419 people born during one week in 1958 and 16,771 people born during one week in 1970.

When the children were aged five to seven years old, mothers were asked whether they had breast fed their child. Responses indicated whether the child had never been breast fed, breastfed for fewer than four weeks, or breast fed for four weeks or more.

When the children were aged 10 to 11 years old, the father’s social class was measured using the Registrar General’s Social Class, which is based on the assumption that society is a graded hierarchy of occupations. The father’s occupation was graded as unskilled/partly skilled, skilled (manual), skilled (non-manual), and managerial/professional.

In addition, when children were aged 10 to 11, brain function was tested using a variety of tests and emotional stress was assessed by mothers and teachers.

The researchers looked to see if there was a link between being breastfed and participant’s Registrar General’s Social Class (profession) at 33 to 34 years of age after adjusting for the father’s Registrar General’s Social Class at 10 to 11 years of age and gender.

Upward mobility was defined as having a higher social class at age 33 to 34 than the father’s social class at 10 to 11 years, and downward mobility was defined as having a lower class than their father.

The researchers employed a number of statistical techniques to account for missing data and to try and estimate the effect of breastfeeding by accounting for other factors that predict breastfeeding. 

What were the basic results?

In the 1958 group, 68% of mothers breastfed their children, while in the 1970 group, only 36% of mothers breastfed.

Breastfeeding was socially distributed in both groups, with children of fathers in higher social classes more likely to be breastfed, but the pattern in the two groups was different. In the 1958 group, breastfeeding was common in all social classes. In the 1970 group, the distribution between social classes was much more pronounced, with mothers from the professional classes far more likely to breastfeed than those in the unskilled classes.

People who were breastfed were more likely to be upwardly mobile (24% increased odds for both those born in 1958 and those born in 1970), and were less likely to be downwardly mobile (approximately 20% reduced odds) compared to people who weren’t breastfed.

Markers of brain function and stress were responsible for approximately 36% of the relationship between breastfeeding and social mobility.

How did the researchers interpret the results?

“Breastfeeding increased the odds of upward social mobility and decreased the odds of downward mobility. Consistent with a causal explanation, the findings were robust to matching on a large number of observable variables and effect sizes were alike for two cohorts with different social distributions of breastfeeding. The effect was mediated in part through neurological and stress mechanisms.”

Conclusion

This large British study adds to the evidence on the health benefits of breastfeeding by finding a link between breastfeeding and increased chances of upward mobility and decreased chances of downward social mobility.

The effects were explained in part by cognitive test scores – indicators of brain development and function.

Cohort studies such as this cannot show that breastfeeding is responsible for the differences in social mobility seen, as there may be other factors that are actually responsible for the link. However, similar results were seen in two cohorts (the 1958 group and the 1970 group) despite different social distributions of breastfeeding.

Also, the researchers used statistical methods (called propensity score matching) to try and control for other factors that may predict breastfeeding.

Additional limitations are that breastfeeding was self-reported by mothers when children were five to seven years old, and there may have been some inaccuracies in recall. Study of populations born more recently may also be valuable.

In particular, when considering the 1958 cohort, factors that may have influenced the decision to breastfeed then (when a larger proportion of mothers would not be working), may differ from those facing today’s mothers.

It is not known whether it is the content of breast milk or the process of breastfeeding itself that is important.

The researchers recommend that more research is performed to examine the link between breastfeeding and a child’s brain and socio-emotional development.

This study has been published in a timely manner, coinciding with Breastfeeding Awareness Week.

Read more advice about getting started with breastfeeding:

Analysis by Bazian
Edited by NHS Choices