Tag Archives: Ethnicity

Ethnicity, birthweight and growth in early childhood

Birthweight varies according to ethnic group but height at the age of five does not. Why might that be? Does it tell us anything about the lives of second and third generation immigrants? And does it offer any useful guidance to health professionals hoping to target disadvantaged groups? Professor Yvonne Kelly outlines recent research with colleagues at the ESRC International Centre for Lifecourse Studies looking at differences in birthweight and early growth between ethnic groups.

Birthweight is important. There is a large body of work that suggests links between low birthweight and the development of chronic disease. Height at the age of five is a less straightforward indicator but still an important measure. The relationship between the two is important as well. Rapid post-natal growth may also have a role in later disease risk, and any correlation may tell us something about the lives of people born in the UK to parents born elsewhere.

Earlier research shows that babies born to South Asian and Black mothers weigh up to 300g less than those with White mothers. They are also up to two and a half times more likely than their White counterparts to have low birthweight.

Our study made use of the rich information available in the Millennium Cohort Study and enabled us to drill down further into ethnic differences. We were able to look at White, Indian, Pakistani, Bangladeshi, Black Caribbean and Black African groups.

These, of course, are groups that have very different migration histories. The Black Caribbeans and Indians mainly migrated to the UK in the 1950s and 1960s. The Pakistanis arrived in the 1960s and 1970s, the Bangladeshis in the 1980s and the Black Africans in the 1990s.

Social v biological

If you accept that ethnicity is a social not a biological construct, these variations must be the result of factors that are not intrinsic to the group but tend to go with membership. Relevant factors are likely to be either socioeconomic or maternal.

So, if one group tends to have higher incomes and higher levels of educational attainment, it is likely to have fewer babies with low birthweight. Similarly, if mothers within one group are less likely to smoke they too are likely to have heavier babies.

Because our research compared data on birthweight to those on ethnicity, socioeconomic status and maternal characteristics, it was possible to identify which were most closely associated.

The results suggest that socioeconomic factors are important in explaining birthweight differences in Black Caribbean, Black African, Bangladeshi and Pakistani infants. Maternal characteristics are important in explaining birthweight differences in Indian and Bangladeshi groups. Clearly, both must operate to some extent in all cases.

Our study identifies the dominant factor for each ethnic group and recommends policy-makers pay attention to the different socioeconomic and culturally related profiles of ethnic minority groups when devising policies aimed at reducing inequalities in birthweight.

A question of height

One key maternal characteristic identified was height. Mothers from the Indian, Pakistani and Bangladeshi groups were on average 8cm shorter than White mothers. We speculate that it might take several generations for individuals within ethnic groups to reach their height potential.

And it could be that increases in maternal height do not happen so much for the first couple of migrant generations due to the ‘accumulated effects of disadvantage, including racism, discrimination and poverty that are disproportionately experienced by migrants’. That idea was put to the test in a second study also using MCS data.

The primary aim of this research was to investigate ethnic differences in height at 5 years of age. The same ethnic groups were used. Again, the sample was large and broadly representative of the whole UK.

Playing catch up

In contrast to the findings on birthweight, Indian, Pakistani, Black Caribbean and Black African children were taller than White children at age 5. Bangladeshi children were the same as White children. Birthweight was not entirely irrelevant. It was a weak to moderate predictor of height in White, Pakistani, Bangladeshi and African children.

All the measured variables favoured the White group over all ethnic minorities. This is consistent with the suggestion floated towards the end of the first study that what is happening is that a generation is ‘catching up’, earlier generations having been previously thwarted by such factors as poor nutrition in underdeveloped home countries.

Saying that, catch-up growth is likely to explain only a part of the ethnic height differences identified and further research is important here. It is also important to note that taller children are more inclined to obesity and so the height advantage of ethnic minority children might not translate into a health advantage in adulthood.

The links between ethnicity, birthweight and height in childhood are not, then, straightforward or by any means fully understood. It is clear that outcomes associated with different groups are the result of social and not biological characteristics.

The length of time a group has been established in the UK also appears to play a part with at least some suggestion of a generational ‘catch-up’ effect. Though there may be plenty of inequality left to address, that does at least suggest things are moving in the right direction.

Further information

Why does birthweight vary among ethnic groups in the UK? Findings from the Millennium Cohort Study is research by Yvonne Kelly, Lidia Panico, Mel Bartley, Michael Marmot, James Nazroo and Amanda Sacker and is published in the Journal of Public Health.

Ethnic differences in growth in early childhood: an investigation of two potential mechanisms is research by Amanda Sacker and Yvonne Kelly and is published in the European Journal of Public Health.

Photo credit: moinuddin forhad

[1] Ethnic differences in growth in early childhood: an investigation of two potential mechanisms. A. Sacker, Y. Kelly

Can a child’s ethnicity tell us something about asthma?

Asthma and wheezing illness are some of the most common childhood illnesses, and appear to have been on the rise in many developed countries. In the ongoing battle against them, considerable research has looked at the links with the surroundings we live in. From the effects of cold weather to dusty homes and living in polluted cities, hundreds of academics and health professionals have tried to put their finger on what external factors might be playing a role in children’s poor health.

Few researchers have looked to see whether there may be a story to tell about links with a child’s ethnicity and whether certain ethnic groups are at higher risk of wheezing illnesses. But now, as part of a wide-ranging ethnicity research project, a team based at the ESRC International Centre for Lifecourse Studies at UCL has been doing just that, as Lidia Panico explains.

About one in five British children has been diagnosed with asthma by a doctor, according to figures from the Health Survey for England, which also shows that wheezing is most common among Black Caribbean children, while Bangladeshi and Black African children suffer least.

A systematic review of UK studies has also found that South Asian children have lower rates of asthma and wheezing illnesses than the general population. In the US, Black children are twice as likely to suffer from asthma than White children. So why do these ethnic differences exist and can they inform our efforts to tackle the problem?

There are quite a few challenges around research in this area and real evidence is thin on the ground, especially when it comes to very young children. Studies have tended to group children from different ethnic backgrounds together or focus only on school age children. Numbers aside, very few studies have been able to go a step further and try to look at what might be behind any observed differences.

Background and biological factors

In our research, we made use of the Millennium Cohort Study, which has been following the health and development of some 20,000 children born in the UK around the turn of the century. This fantastic study has lots of data. This enabled us to look at a host of background and biological factors that might be at play. We looked at the children when they turned 3 years old.

We were able to look at household income, whether mum and dad had jobs and what those jobs were, mum’s age when she gave birth to the child and whether mum lived on her own.

When it came to potential biological causes, we could look to see if parents were smokers, whether the child shared his or her home with other siblings, potentially increasing the risk of catching common infections, furry pets and whether the child had been breastfed.

Other things taken into consideration were whether English was spoken at home and parents’ migration status.

Survey respondents (usually the mother) were asked whether the child had ever suffered from asthma and whether they had had problems with wheezing in the previous 12 months.

Facts and figures

Around one in ten of the children had suffered from asthma at some point while two in ten had wheezed in the last year. Around a fifth of those who had been wheezy in the last year had had more than four attacks in that period with nearly a quarter of them had their sleep disturbed by wheeze on a weekly basis.

As far as ethnic differences were concerned, Black Caribbeans were around 70 per cent more likely than their White counterparts to have had asthma ( 16.2 per cent compared with 11.6 per cent), while Bangladeshis were much less likely at 5.6 per cent.

When we looked at wheezing in the previous 12 months, more than a quarter of Black Caribbean children had suffered compared with one in five White children, so around 40 per cent more likely. Around half of the disadvantage could be explained by social and economic factors, in particular income and the receipt of benefits.

Once again Bangladeshi children were least likely to have wheezed at less than one in ten , especially if their mother was born abroad and if they were living in a bi-lingual or non-English speaking household.

Black African children had lower asthma and wheezing rates than White children, while Indian and Pakistani children had similar rates to White children.

Lower reported rates

Our research team is inclined to think that the apparent South Asian “advantage” might be due to lower reported rates among the Bangladeshi group and should not be attributed to all Asian groups.

With work in the UK and US suggesting South Asians are more likely to be hospitalised with asthma than White children, there is either a story around levels of severity or under reporting/ under diagnosis among these ethnic groups.

Our data suggests that households that would have the most problems communicating with British health services, (new migrants/those who don’t speak English a home or need the survey translated) are least likely to report asthma and wheeze.

By contrast the Black African group which has a similar migration history to the Bangladeshi group, but where English is spoken more frequently, do not show signs of under-reporting.

Migration status and language are key

In order to avoid potentially misleading reports of low asthma and wheezing illness prevalence in some ethnic groups, we should look carefully at migration history and levels of spoken English, particularly in primary care settings.

Ethnic groups are diverse in terms of the prevalence of asthma and wheezing and in their social and economic profiles.

It is also clear that child health provision needs to be carried out within the unique social, economic and cultural context of each group if progress is to be made.

Further information

Lidia Panico is a researcher based at the French Institute for Demographic Studies.

Ethnic variation in childhood asthma and wheezing illnesses: findings from the Millennium Cohort Study is research published in the International Journal of Epidemiology by Lidia Panico, Mel Bartley, Michael Marmot, James Nazroo, Amanda Sacker and Yvonne Kelly.

Photo credit: KristyFaith