MRC National Survey of Health and Development/1946 birth cohort

March 1946: the first national maternity survey


In 1946 a survey of all the mothers who gave birth in a week in March in England, Wales and Scotland was undertaken to learn about the social and economic costs of childbearing. Health visitors visited the mother at home to ask about her ante-natal and post-natal care and about the family's social and economic circumstances, the baby's weight was extracted from birth records, and their survival during infancy was followed up.

Concern over the falling national birth rate and the health of the population were reasons why the original survey was undertaken. As it turned out this cohort of births was the beginning of the post war baby boom.

Information was also needed to help assess how effective were midwives and obstetric services, both in preventing infant deaths and in promoting the health of mothers and infants. The survey found that not all mothers had access to pain relief in labour and this led to changes to allow midwives to administer gas and air. The survey also found that 26 in every 1000 babies died within the first month after birth. In 1946 babies born to mothers in the poorest economic circumstances weighed less at birth and were almost 4 times more likely to die in infancy than babies born to the most economically advantaged mothers.

Studying this generation is interesting for many reasons not least because they are the first group of people in the UK to live most of their lives with access to a National Health Service (NHS), which was created in 1948.

The first national birth cohort study

James Douglas
Dr James Douglas

Dr James Douglas who was responsible for the maternity survey was able to obtain funding to follow up 5362 of the babies from this cohort. He became the first director of the first national birth cohort study which became known as the National Survey of Health and Development (commonly called NSHD or the 1946 birth cohort). These people are still being followed up today and, since 1962, the study has been funded by the Medical Research Council. The first follow-ups, at 2 and 4 years, were designed to study growth and health in relation to social and economic circumstances and care.

From school to young adulthood

Between 6 and 31 years (inclusive) there were 15 follow-ups. During the school years the study was concerned with physical and mental development, and with educational attainment and pathways through the educational system. Policy relevant findings were particularly concerned with adverse effects of restricted parental access to children in hospital, and the effectiveness of the selective secondary school system. The research led to improved hospital visiting for families. Cognitive tests were specifically designed for the study by the National Foundation for Educational Research and administered to study members by school teachers. The study found, for example, that for children with similar cognitive test scores, the children from more socially advantaged homes were more likely to pass the 11+ and be offered the chance to go to a grammar school than the children from less advantaged homes. This 'wastage of talent' was of great concern to policy makers and evidence from the study contributed to a number of changes in educational policy.

In adolescence and young adulthood the study was particularly concerned with how education, childhood health and the home environment shaped future choices in occupation and respiratory disease. The study found, for example, that study members who, as infants, had experienced chest illness or had lived in crowded homes were more likely to suffer from respiratory symptoms and chest illness in their twenties.

1982-2006: a change in emphasis

James Douglas
Professor Michael Wadsworth

From the early 1980s, when the cohort were in their thirties, Professor Michael Wadsworth, the second director, focused the study more on health and how health and function changed as study members grew older. Trained research nurses visited study members at home at 36, 43 and 53 years and measured body size (such as height, weight, chest, waist and hip circumference), blood pressure and lung function as well as asking about mental and physical health and life circumstances.  At 43 and 53 years a range of tests of cognitive capability were administered and, at 53 years, tests of physical capability were included. Between 47 and 54 years, and again at 57 years, women study members were sent postal questionnaires to obtain information on timing of menopause and other characteristics of relevance to the women's midlife health.

At the same time there was a growing interest in theories about the developmental origins of adult disease, supported by evidence from this study and from other cohort studies. Investigators of this study showed how social and biological factors from early life had a long-term influence on later health and function.

The study today: another change of emphasis

NSHD building, Edinburgh

Professor Diana Kuh, a member of the NSHD research team since 1987, became the study's third director in 2007. The research team is now developing the NSHD into a life course study of ageing, to make best use of all the information that study members have so kindly given over their lives. This information is what makes the study such a scientifically valuable and unique resource. In their early sixties, study members were invited for the first time in adult life to research clinics around the country, where detailed investigations of the heart, blood vessels, muscles and bones were carried out, blood and urine samples obtained for analysis, as well as the core measures of function, capability, mental health and life circumstances being repeated.

Cardiff team

Study members report very high satisfaction with these visits and the team provides them and their GPs with clinically relevant results from the assessment. These data, along with data already collected in earlier life are allowing us to test a whole range of hypotheses about healthy and normal ageing. We will also study the group who appear to be ageing faster than others and those at greater risk of chronic disease to try to identify the social and biological factors earlier in life that may explain why they are most at risk.

There is great value in performing inter-cohort comparisons to test whether a finding in one study can be replicated in another. Where similar findings are shown across studies this provides more robust evidence on which to base changes in policy, practice and prevention. NSHD researchers are now leading two such initiatives, including HALCyon, and participating in many others. 

Findings

Key findings from the study include:

  • Men and women who had been low birth weight babies had higher blood pressure at 36, 43 and 53 years than those of higher birth weight
  • Men and women whose fathers had non-manual occupations had lower blood pressure and obesity, and better lung function and  cognitive and physical capability in adult life than those whose fathers had manual occupations
  • Women whose fathers had manual occupations were twice as likely to die between 26 and 60 years than women whose fathers had non-manual occupations
  • Women who were breastfed as babies, who scored higher on the childhood cognitive tests or who had more children than others had a later menopause than other women
  • Women of higher birth weight or who grew faster than others in childhood were more likely to be diagnosed with premenopausal breast cancer than other women
  • Men and women of higher birth weight had stronger grip strength at age 53 years
  • Men who gained weight faster before 7 years and then put on less weight as adults had better physical capability at 53 years than those who gained weight more slowly in the early years but then gained weight in adult life.
  • Most adolescents with depression were mentally healthy in adult life
  • Adult education or further training benefits cognitive capability

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