Cohort Profile: The Born in Bradford multi-ethnic family cohort study

The Born in Bradford cohort study was established in 2007 to examine how genetic, nutritional, environmental, behavioural and social factors impact on health and development during childhood, and subsequently adult life in a deprived multi-ethnic population. Between 2007 and 2011, detailed information on socio-economic characteristics, ethnicity and family trees, lifestyle factors, environmental risk factors and physical and mental health has been collected from 12 453 women with 13 776 pregnancies (recruited at ∼28 weeks) and 3448 of their partners. Mothers were weighed and measured at recruitment, and infants have had detailed anthropometric assessment at birth and post-natally up to 2 years of age. Results of an oral glucose tolerance test and lipid profiles were obtained on the mothers during pregnancy at ∼28 weeks gestation, and pregnancy serum, plasma and urine samples have been stored. Cord blood samples have been obtained and stored and Deoxyribonucleic acid (DNA) extraction on 10 000 mother–offspring pairs is nearly completed. The study has a biobank of over 250 000 samples of maternal blood, DNA and urine, cord blood and DNA and paternal saliva. Details of how scientists can access these data are provided in this cohort profile. Born in Bradford (BiB) was created in response to rising concerns about the high rates of childhood morbidity and mortality in the city of Bradford, the sixth largest city in the UK with a population of about half a million and urban areas that are among the most deprived in the UK. Around 20% of the population of Bradford is of South Asian origin (90% of whom are from Pakistan), and this constitutes a three-generation community that maintains close links with Pakistan.1 The relatively young age of the population of Pakistani origin and their higher fertility rates, compared with the White British majority population, explain why almost half of babies born in the city have parents of Pakistani origin. Sixty percent of the babies born in the city are born into the poorest 20% of the population of England and Wales based on the British government’s residential area Index of Multiple Deprivation.2 Infant mortality in Bradford has been consistently above the national average, peaking at 9.4 deaths/1000 live births in 2003, when the national average was 5.5 deaths/1000 live births, and levels of congenital anomalies and childhood disability are among the highest in the UK.3–10 The cohort was established in 2007 with the broad aims to: describe health and ill health within a multi-ethnic (largely bi-ethnic) economically deprived population; identify modifiable causal pathways that promote well-being or contribute to ill health; develop, design and evaluate interventions to promote health; provide a model for integrating operational, epidemiological and evaluative research into practice within the National Health Service and other health-related systems; and build and strengthen local research capacity in Bradford. BiB examines how genetic, nutritional, environmental and social factors impact on health and development during childhood and, with ongoing funding, will also examine long-term effects into adult life. The ultimate goal is to develop hypotheses, which can then be evaluated and tested for health and social interventions to improve childhood and adult health. Specific research objectives currently being tested are linked to substudies, which include investigations of factors related to differences in birth size and adiposity, infant care practices and sudden infant death, in utero renal development, the health effects of environmental and dietary exposures in pregnancy, vitamin D levels and pregnancy outcomes, viral infection exposure on immune response, development and prevention of childhood obesity and understanding the genetic determinants of growth, adiposity and diabetes risk. A number of these studies include a particular emphasis on differences between individuals of White British and those of Pakistani origin. Of relevance to building local research capacity, several of these substudies support postgraduate Masters and PhD students. A full list of substudies and PhD projects is described on the programme’s website (www.borninbradford.nhs.uk). An initial BiB planning and development team undertook a wide consultation with community, neighbourhood and faith groups in the city to make them aware of our plans for a cohort study and to elicit areas of community interest. Our presentations about the patterns of ill health in the city, particularly the high infant mortality rate and high levels of morbidity in children, including obesity, encouraged groups to express strong support for our proposed study. Additionally, community consultation revealed public concern about the effect of environmental toxins, particularly air pollution, on health, with asthma in children identified as an important problem. An area of considerable sensitivity in the city was that of genetic disease. This was disproportionately present in the Pakistani community and had been linked with the prevailing practice of marriage to first cousins and other blood relations.11 Although local groups were prepared to discuss what they recognized as an area of justifiable concern, they were keen for future discussions to be culturally sensitive and to be based on sound scientific evidence that included exploration of potential social and well-being benefits, as well as adverse effects of such unions. During the course of recruitment, we have been successful in obtaining grant funding to allow us to undertake long-term follow up of two subcohorts. We also have funds to link the entire cohort to external data, including long-term follow up of two subcohorts, one over 2000 participants that is concerned with risk factors for allergic disease in infancy and another a different 1700 participants concerned with risk factors for obesity. Bradford has one maternity unit based at Bradford Royal Infirmary. The unit is one of the busiest in the UK with over 6000 new births each year. All women booked for delivery at the Bradford Royal Infirmary are offered an oral glucose tolerance test (OGTT) at 26–28 weeks gestation, requiring a test and retest over 2 h. Around 80% take up this offer. Study information was given to women by their midwife at their booking appointment and they were invited to take part. On attendance at the OGTT clinic, full consent was obtained for recruitment to BiB, and the woman was invited to complete an interviewer-administered questionnaire. Between March 2007 and November 2010, >80% of the women who attended the OGTT took up the invitation, and we recruited 12 453 women with 13 776 pregnancies to the cohort, with OGTT results for 11 442 of them. All babies born to women who agreed to participate in the cohort study were eligible for recruitment. Partners of the women who were recruited to the cohort were also invited to participate. Only a small proportion of fathers attended the OGTT clinic with their partners. Others were approached when they attended the hospital with their partner for other appointments or when a member of the study team visits the family home during follow-up visits to see mother and baby. Figure 1 describes the recruitment figures for the cohort. Recruitment statistics Almost half of the South Asian population in Bradford is of Mirpuri origin. Mirpur is a predominantly rural district in the province of Azad Kashmir in Pakistan. Some members of the community do not read or speak English. However, the majority are able to understand Urdu or Mirpuri, although not all are literate in Urdu. To ensure consistency, the baseline questionnaire was transliterated into Urdu and Mirpuri using a standardized process, so that words and phrases corresponded with the original English version. A further complication of translation was that Mirpuri does not have a written form. Bilingual interviewers, trained in use of the transliterated versions, were employed to administer the questionnaires. A total of 9319 (81.9%) women completed the questionnaire interview in English, 1468 (12.9%) in Urdu, 547 (4.8%) in Mirpuri and 11 (0.1%) in other languages. In 32 (0.3%) cases, the language used was not recorded. A minority of the pregnant women (17.3%) were offered but did not attend the OGTT clinic and were recruited through other contacts such as hospital appointments or during their hospital stay for the birth. As the study is locally based with just one maternity unit, we are able to determine the proportion of women eligible who have been recruited to the study and also to compare the study population data with data on all births in Bradford. Table 1 compares characteristics between these participants with those not recruited (either because they were not approached or declined). There are a number of small differences between the recruited and non-recruited cohorts. We recruited a lower proportion of younger mothers (age: 20–24 years) compared with mothers not in the cohort and a higher proportion of South Asian mothers and nulliparous mothers. Differences in gestational age and preterm delivery may be explained by recruitment to BiB occurring late in pregnancy, and therefore we did not have the potential to recruit those born before 26–28 weeks. Comparison of BiB cohort with all other births at the maternity department in Bradford Teaching Hospitals Trust—2007–11 *Ethnic groups assigned using Nam Pehchan. aBased on singleton births only. bIn the BiB cohort, this consists of records where mothers have given birth outside the BRI. IMD = Index of Multiple Deprivation; SD = Standard Deviation; BRI = Bradford Royal Infirmary. Comparison of BiB cohort with all other births at the maternity department in Bradford Teaching Hospitals Trust—2007–11 *Ethnic groups assigned using Nam Pehchan. aBased on singleton births only. bIn the BiB cohort, this consists of records where mothers have given birth outside the BRI. IMD = Index of Multiple Deprivation; SD = Standard Deviation; BRI = Bradford Royal Infirmary. Follow up of the cohort is variable and dependent on funding linked to specific substudies. Figure 2 describes the follow up in the whole cohort and the key subcohorts and data collected. Data collection—parents and child from birth to 4 years At birth, the details of the delivery, birthweight and a summary record of antenatal information are entered into maternity and radiology information systems, and we are able to link to these data for all study participants. Umbilical cord blood samples were collected and stored in the biobank at −80°C, alongside maternal blood samples taken at recruitment. Study administrators visited the post-natal wards and identified all BiB mothers. Their babies had their abdominal circumference measured, along with head circumference and subscapular and triceps skinfold thickness, before they were discharged. All babies were visited by a health worker at ∼2 weeks, 7 weeks and 8 months. Growth measurements, breastfeeding and immunization data are recorded on child health record and child health information systems. These data are extracted and imported into the main BiB database, linked by National Health Service numbers. Growth measurements by the school nurse will be collected at 4 and 6 years and we will also link to these data for all participants. A congenital anomalies register has been established in the city as part of BiB. Details on all children with possible congenital anomalies are reported by paediatricians, geneticists and by other specialists who identify them in clinics, and these are entered into the database that is linked to the main BiB data. The advent of electronic health records provides new opportunities for cost-effective follow up of health outcomes. We have developed systems for linking and capturing routine data from primary and secondary care, such as attendances, diagnoses and We have also with local to link future from the National for BiB our and with other birth for Study of and we that a is in detailed of all participants as they age through childhood and into and we that such follow up in BiB be a scientific to research the genetic and health characteristics of a multi-ethnic population. We also the and to follow up on the whole cohort the record described and these with detailed follow up on during the years and then funding for a detailed assessment of all participants when the children are Follow up with research visits in two because the original was to data on a of is concerned with risk factors for childhood obesity, and the and is concerned with the between specific viral and allergic in the initial recruitment has recruited over 1700 in which the children were born between and for this was obtained to the and identify modifiable risk factors for childhood obesity. A community team of visits at home when children are 12 and and and 4 years to this We also research based at the hospital as an for mothers who not to have home but most home We have follow-up rates of for each with of the in at one follow-up the is funding for a of up at the of 1 and 2 This study data on exposures that may be linked to risk for asthma and such as family and infant is taken and stored for for and of and has been obtained to undertake a further of this at the age of 4 recruitment at weeks pregnancy, women were invited for an at weeks as part of a to renal and women and this had measurements on at antenatal and has been obtained for the main study and all of the substudies from the Bradford of of different of data are high for participants recruited to the study at We this the close link between the study and maternity in the hospital and community, the high public of the study on the wide consultation and that has been in and the for women to 2 in hospital to the is also by the of the recruitment team and their in key community languages. The study is in and, not we have of the use of post-natal as a of follow up in response rates and to attend post-natal research clinic appointments were also taken We that such as language and are all factors to the of with these of follow up and therefore have different initial funding, as well as a to the research being to local and us to how we recruitment and follow up into routine health As well as the study we that the of research and practice with translation of into routine health data, collected as part of the care and present in research but had considerable potential to research in routine During we developed and recruitment and the baseline questionnaire. Between 2007 and 2011, detailed information on socio-economic characteristics, ethnicity and family trees, lifestyle factors, environmental and neighbourhood air and physical and mental health were collected on women recruited at ∼28 weeks A related but data has been obtained from their partners. Mothers were weighed and measured at recruitment and infants have had anthropometric assessment at birth and post-natally up to 2 years of age. Details about the recruitment and data are described in a Table 2 describes the data collected at baseline and follow up for the full cohort and the the of data is on growth, physical and the the is on exposures that may be linked to risk for asthma and such as family and infant Born in Bradford data of = = Born in Bradford data of = = BiB has a biobank of over 250 000 samples of maternal blood, DNA and urine, cord blood and DNA and paternal as data at blood samples from the children are stored for for and of and recruitment has been completed and so at this are and for of the we that the are Table describes how the baseline characteristics of the mothers by Pakistani origin mothers were on average and White British origin mothers. Pakistani mothers were to be but were to be employed White British mothers. Pakistani mothers reported during pregnancy, and reported in to a high of and use in White British mothers. Pakistani origin mothers reported patterns of to White British reported they were compared with a Pakistani origin mothers took an and were in of White British mothers. 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This response the of opportunities to who for the most part do not attend the clinic for their appointments and are not in the during home visits to the of the to take part. This of is not to that for other birth based on specific including the cohort. The cohort of fathers who to will provide opportunities to study them in their and to at family a in other birth cohort The BiB further details about the research study and about the study. from and from are also We with other The BiB has details of how to of and has for All will be by the BiB on a and we to to potential within 8 weeks. The Born in Bradford study research by the National for Health for Health and and the for funding The in this are those of the and not those of the the or the of We are to all the who took part in this to the for their in the and health and to the BiB team that included interviewers, data research scientists and and of of all the recruited are in the poorest of for England and and are of Pakistani origin. This provides a relatively minority with a to diabetes and disease and with a high of genetic We have collected detailed and for all in the with completed by trained Additionally, family were completed with mothers who that they were related to the of their baby. This that BiB can make a to understanding the of patterns and on health and The characteristics of mothers and of babies by This is in and where were lower in in family characteristics where a majority of Pakistani origin mothers were related to the of their in marriage patterns and in the where were to be but to be employed and in health-related where and during The study has that birth and childhood anthropometric measurements collected in practice are the lower birthweight in Pakistani origin infants compared with White British origin infants is the Pakistani origin parents were born in the UK or in the of infants in this population of the key from that by BiB has been able to link community, primary care systems and records to provide follow-up data. has the of research and practice and provides a strong for translation of research into care, with of how research can