We spoke to people who had taken part in or been invited to join cohort studies. The term ‘cohort study’ was often unfamiliar and could be confusing.
What are cohort studies?
A cohort study identifies a group of people and follows them over a period of time. The aim is to look at how a group of people are exposed to different risk factors which may affect their lives. Cohort studies can look at many different aspects of people’s lives, including their health and/or social factors. Cohort studies can be prospective (meaning that data are collected as individual lives unfold), or retrospective (meaning that researchers look at historical data about individuals after a certain outcome, such as diagnosis with a disease, has occurred).
Cohort studies can collect data on people that covers a long period of time. The longest running is a British birth cohort study which started in 1946 when study members were born and has now been following-up participants for over 70 years.
Jenny, a senior researcher, describes what a cohort study is.
There are various designs of cohort studies. Some are referred to as ‘birth cohorts’, because the people within the group being researched were born in the same time period (a week, a year, a few years) and/or location (city, region). Some cohort studies are interested in a particular health condition or event and follow people who have experience of these (such as having motor neurone disease/MND, or having had a transient ischaemic attack/TIA/’mini stroke’ or stroke). Other studies involve healthy volunteers. Across the people we spoke to, there were experiences of all of these different types of cohort study and other types of medical research.
A number of biobanking studies recruit large groups of people across the population, collect samples from them over time, and then look at the data to try and work out why some people go on to develop particular illnesses when others don’t. Some biobanking studies recruit healthy people from across the population. Others look at particular conditions, such as motor neurone disease (MND), and recruit people already diagnosed with the condition and sometimes healthy volunteers too. You can find more about biobanking studies here.
The length of time that studies can last varies. For some people we spoke to, the study they were involved in was ongoing. For others, the study had closed and/or their participation in it had stopped. Most people we spoke to were comfortable with the length of time their study was running for, although some people who had been in birth cohort studies for many decades were surprised that the research was still going.
Jenny, a senior researcher, talks about the difference between a prospective and retrospective cohort study.
Alan Z is part of a five year renal (kidney) study. He doesn’t feel this is too long a commitment, and that it is a good length of time for the researchers to gather data.
We spoke to people who had taken part in a number of different cohort studies. These studies varied in terms of how long they had been running, what taking part involved, what the research topics and study aims were, the characteristics of the participants, and so on. In this Healthtalk resource, we haven’t directly named the specific cohort studies that people took part in but some details about study aims and activities mean that the studies are identifiable.
For some people, there were certain features of the cohort study that were meaningful to them. This included studies looking at people born in a particular time frame (the same week, or same few years) or location (a city or region). Linda, who took part in a birth cohort study, reflected on her upbringing and how times had changed. Barbara said she “now feels quite privileged to be part of this study” because it was unique and pioneering in the length of time it had been running. Margaret also said she felt “very proud” to be part of her study. Nadera and Mr S took part in a study focused on their home city and they talked about there being high rates of health problems, like diabetes, and obesity.
A few people, like Emily and Keith, had taken part in more than one cohort study. Brian, for example, was part of a birth cohort study and a biobanking study. Sometimes they could remember distinct differences between them; other times, their experience of studies blurred together. A few people found it difficult to separate out their experiences of health care in general and their experiences of health research, sometimes they felt that the two overlapped or were the same thing.
Why are cohort studies important?
In a general sense, most people we talked to felt that the studies they had taken part in were important. As Iram said, these studies are ultimately being done “to help people”. Often people said they hoped the studies would lead to improved knowledge about health. Margaret highlighted some important findings that had come out of these types of studies, such as the links between smoking and lung cancer. Ian was in a biomarker study (looking at particular characteristics of the samples) which “seems to be on the verge of some exciting results, and we’ll wait and see what happens.”
Jenny, a senior researcher, describes why cohort studies are important.
Some people emphasised that cohort studies had a unique and special role in improving understandings about health. Keith talked about cohort studies gathering “information on a grand scale and over a long time.” Teresa felt it was valuable to have data “that spans a lifetime.” Barbara felt that, as the study she participated in had “gone on and on, it just seems more and more important.”
People talked about cohort studies allowing researchers to make ‘links’ or ‘connections’ and to see ‘patterns’ and ‘trends’ associated with certain outcomes. Lucy saw cohort studies as important for being able to “isolate socioeconomic or other factors that might be influential.” Douglas recognised that there could be unexpected factors and that researchers “might pick up something that is important which might not be important to me but might be important to them” and their research aims.
Alan Z sees cohort studies as having an important role in understanding health in relation to lifestyle and diet.
Margaret feels birth cohort studies like hers are needed to improve our understanding about medical and social issues.
Mr S describes cohort studies as allowing links to be made between risk factors and outcomes in health.
Others were unclear how cohort studies were different to other types of medical research. For some, the differences between types of medical research wasn’t important; most felt that, providing the outcomes of research were to improve health and healthcare practice, then it was a good thing to support.
Often people thought future generations would benefit from these studies and didn’t expect there to be any direct benefit from the findings for them. Some hoped though that they and other people like them would also benefit. Eisha felt there were lots of everyday things that cohort studies could make better, such as improving green spaces, advising on oral hygiene, and encouraging dads to be more involved with their children.
By improving knowledge about health, many people felt that these studies could then improve the practices of healthcare professionals and treatment options. Alan Y explained, “It’s knowledge for them [doctors] and the more knowledge they have, the better healthcare they can give down to people like me.”
John is pleased to be a data point and to see research moving forward.
Jenny, a senior researcher, explains why it is often a long time before findings can be drawn out of a cohort study and shared with others.
Some people had a clear grasp of the aims of the specific cohort studies they had taken part in. Others were unsure, sometimes because they had begun participating many years ago and had now forgotten this information. Most people in this situation were not worried and they felt confident that the research was being done for “a good reason”, whatever that reason was.
Derek couldn’t recall the details of why the study was being carried out, but he felt sure that it was “for good purposes”. Ronald felt that the study “must have ended up helping people somehow. But I wouldn’t know how”, otherwise it wouldn’t have been continued. Margaret Ann said, “If someone somewhere down the line thinks this is interesting, well I’m quite happy to answer the questions.” As a child, Jade withdrew her participation in a twins study but is now thinking about re-joining. She thinks it would have helped if a researcher had explained the value of this type of study at the time and the types of questions they hoped the research might answer.
Whilst Nadera felt research was important to enhance knowledge about health, she was also keen to see more action to improve people’s lives, including around poverty and access to healthy foods. She felt that some studies don’t lead to any actual change.
Some people, like Ian, felt that the researchers running these studies were themselves unsure about how they would use or share the data collected in the future. Ian thought that there might be new and unexpected uses of his data, which he saw as a positive thing, and that data sharing with other researchers “could lead to some breakthrough.”
Ian had blood samples taken as part of a motor neurone disease (MND) study. He isn’t certain how the researchers will use these samples to meet their research aims but feels okay about this.
Lucy knows she has been in a study since she was a baby but doesn’t know the name or the aim of it.
However, not everyone we interviewed felt this way and some had concerns. Richard declined to take part in a biobanking study because it wasn’t clear exactly what the study was hoping to achieve. He explained, “Probably I felt some misgiving about the nature of it, in as much as it’s a long-term study without specific aims that I could identify… the non-specificity of it.” After a long gap without communication from the research team, Isobel had attended an event where they shared some findings. However, because she didn’t know much about the background, she said it made her feel “out of my depth” and “ill-informed” about the purpose of the study.
Often people said they would like to understand more about the study they had taken part in, especially what it aimed to find out and what is has found out so far (see also sections on communication with research staff and key messages to research staff). Lucy has been in a study since she was a baby and found it an “annoyance actually that I just don’t know anything about the study.” She couldn’t remember if it had been explained to her when she was older or if the researchers had “just assumed” she already knew.
The future of cohort studies
A few people talked about the future of the specific studies they were part of. Some people taking part in birth cohort studies wondered when their study would end and said that they hadn’t thought it would have lasted as long as it has.
Jess remembers a question from the survey she filled in when she was a child. She didn’t expect the study to still be following her up so many decades later.
Some cohort studies involved sub-projects with new interests or aims that have developed over time. Some aims had evolved based on new knowledge, technology, the availability of funding and interest from other researchers who would like to use the data.
Barbara is in a birth cohort study which has been extended several times. She thinks that securing funding to continue data collection has always been an issue.
A few people we spoke to had been involved in advising research teams on future sub-studies they were planning. Salma liked learning about and “shaping the research.” Brian thought it was good that the researchers were “consulting us before they start the research.”
Some people who had been taking part in a study for many years talked about noticing when the research took a particular interest in a topic or a new line of inquiry. Often this was noticed in questionnaires. Barbara had completed a questionnaire every few years and she recalled that “there was one year, the survey was all about smoking and cancer; then another year you can just see that there’s an emphasis on maybe heart [health].” Gill and Brian had also noticed new research interests developing over time in the studies they were part of.