What are cohort studies and why are they important in UK health research?
A study which works with a specific group of people to understand how health and wellbeing change over time is often described as a cohort study.
By using this approach researchers gather in-depth information about the factors which affect our health, and how these can change over time. Cohort studies are particularly important to understand the impact of lifestyle, behaviour and the environment. Cohort studies that involve a broad range of people are useful in the development of population based health strategies.
In the UK, cohort studies play a critical role in research, they have broken new ground in understanding the factors which affect human health, informing public health policy and practice and contributing to international health studies.
Cohort studies currently take place across the UK. Participants come from every walk of life, with an estimated 3.5 % of the population having taken part in one or more UK cohort studies (MRC, 2014). Such studies represent a hugely valuable public, scientific and governmental investment in health sciences. More than half of UK cohort studies have been running for over twenty years, representing a unique resource for understanding health.
There are many types of cohort study , from birth cohorts (MRC National Survey of Health and Development, Aberdeen Children Of the Nineteen Fifties, Generation Scotland) and representative population studies (Cognitive Function and Ageing Studies II, European Prospective Investigation of Cancer Norfolk, Caerphilly), through to studies which address specific disease areas (PREVENT, Genetic Frontotemporal Dementia Initiative).
The evolution and adaptation of UK cohort studies
Understanding health and wellbeing over the life course involves multiple interacting factors. Many studies rely on the development of a distinctive relationship between participants and their study teams. These relationships form one of the greatest strengths of cohort studies, enabling them to work closely with participants over many years. Increasingly, cohort studies use cutting-edge technology to improve the quality of the science and to reduce cost. This capacity to adapt and adopt emerging technologies ensures that cohort studies make best use of the investment of both participants and study teams. DPUK is working in collaboration with over 30 UK cohort studies to increase the scope and scale of health research in the critical field of dementia research. By supporting studies to access emerging imaging, genetics and data technologies, DPUK supports cohort development and cross-cohort collaboration. Supporting collaboration enables researchers to draw on the diverse range of detailed information to address increasingly challenging questions about the risk-factors related to the development of dementias.
Such collaborative networks represents a wider evolution in UK science with researchers working together to address key health questions and develop best research practices. Collaborations across cohorts aim to make best use of the rich and diverse data collected by individual studies. Linking health data in new ways, UK research aims to increase the potential of science to understand key health challenges and identify new research questions.
Understanding cohort collaborations and research participation
Social research with individual cohort studies has examined the views and roles of participants in UK health research. However, little work has been done to look at participant experience across different types of cohort and in different regions. Through DPUK, research is being conducted with cohort studies across the UK to understand how collaborative practices are changing participants’ experiences of health research, and ensure that work with cohorts continues to reflect best practice internationally.
References: Maximising the Value of UK Cohorts: MRC Strategic Review of the Largest UK Population Cohort Studies (February 2014). Available HERE.
Case study: An example of a UK cohort study
The MRC National Survey of Health and Development (NSHD) is the oldest of the British birth cohorts and has collected information from birth to the current day on the health and life circumstances of over five thousand men and women born during one week in March 1946. NSHD is a prospective cohort study, in that it follows up a group of people who share certain characteristics, in this case all being born during the same week, in order to investigate how environmental exposures or experiences in earlier life are associated with subsequent health and other outcomes. The NSHD is the longest running study of human development and ageing, and as the study members approach their 70th birthday, it is entering a crucial stage with regards to understanding the increasing risk of dementia and other age-related chronic diseases. The key message from NSHD findings over the last sixty years is that childhood matters for many aspects of adult health and ageing; will this remain true at the oldest ages?
The study began as a maternity survey in 1946, when a survey of all mothers who gave birth during 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. The results from this survey were striking. For example they showed that the quality of care received differed for less well-off mothers compared to those who were better off, and their babies were of lower birth weight and less likely to survive infancy. Concern over these findings led to funding to follow up a sample of 5,362 babies which became known as the NSHD, and is also called the 1946 British birth cohort study. The MRC has funded this study since 1962.
Studying this generation is interesting for many reasons not least because they are the first group of people in Britain to live most of their lives with access to a National Health Service (NHS), which was created in 1948. The participants have been followed up throughout their lives, with questionnaires, cognitive tests and a range of health assessments. These data, along with data already collected in earlier life, are allowing researchers to test a whole range of hypotheses about healthy and normal ageing. Researchers aim to identify the social, psychological and biomedical factors across life that may explain why groups of individuals appear to be ageing faster (or slower) than others and those at greater (or lesser) risk of chronic disease.
One participant, Elizabeth, said: “I felt that I was doing something valuable to contribute to a very important piece of research, the findings of which may well help lots of people in the future.” A short documentary can be found HERE.