In yesterday’s post, Suzi pointed out how Children of the 90s has helped her research, and last Friday, BBC Breakfast had a feature on a study that is already a couple of years old, yet remains very much in its infancy. As with Children of the 90s, ‘Born in Bradford’ is a longitudinal cohort: a study which recruits a group of participants, sometimes well before their birth certificates are signed, and follows them during the course of their lives (often alongside their parents and/or other relatives). Herculean efforts are put in to record buckets of information about them along the way. Such a study is an immensely rich and important resource.
Studies begin with certain goals in mind and develop over time to address new research questions and shifting paradigms in medicine. For example, early work from Children Of The 90s helped to resolve contention about which way we should lie our babies at night to lower the risk of cot death (that’s face up, new parents!). Nowadays, the participants are collectively entering their third decade walking this earth, and continue to help us answer questions about the incalculable complexities of maintaining good health in the 21st century.
Many types of information and measures are recorded by cohorts (all with the consent of participants, of course). These can range from simple questionnaires about things like family income and leisure activity preferences to in-depth measures taken at medical examinations, including blood samples used to measure various biochemical properties. Since the advent of the human genome project in 2003, we are increasingly being able to survey the genetic information of participants to explore what effects our DNA can have on our propensity for developing certain traits or diseases.
All of this is done by recording information in brief windows of time, and it is imperative to get the correct measures taken. Our ability to answer new research questions may well depend on data taken at very specific points in the lives of participants, particularly when examining tumultuous developmental windows such as childhood and puberty. The powers in charge—those who apply for funding to keep the cohort afloat—have to use tremendous foresight to predict what traits and information should be detailed with the finite resources that are awarded.
The reward for continuing investment in a cohort is that they only get more valuable over time. Many factors affecting our health come into play early in life and accrue impact over decades, leading to epidemics of diseases in our more grizzled years. This is the case with chronic illnesses like heart disease: in children, we can pick up traces of adverse lifestyle choices, such as a high fat diet, which suggest an increased risk of suffering from the condition in middle age.
With time, there is also potential to follow up successive generations in a community. It may be a while before those babies in Bradford start doing the romance dance themselves and another generation is bought into this world, but if a cohort can be sustained long enough, we have the ability to examine children of children (the new arrivals being the grandchildren of original study parents). Lord knows how the forefathers of genetics would have pined for trans-generational measures like these to use whilst studying the intricacies of human inheritance.
One of the chief dangers to a cohort is attrition. As a study continues, longstanding participants may die, migrate away, or simply lose interest in being involved any longer (it’s a busy world, after all). Over time, numbers in a cohort can dwindle and these losses leave researchers bereft of vital information. With larger numbers of participants, we have a much greater resolution for detecting marginal factors or rare conditions which can have significant effects or afflict many people in general populations of several million. Great pains are taken to retain as many people as possible, but attrition is inevitable.
Nonetheless, with the continuing enthusiasm of participants and the hard work of huge numbers of staff, studies like Born In Bradford will progress far past when their babies hit drinking age. So get a head start, and raise a glass to birth cohorts.
If you want to know more about birth cohorts, Radio 4 broadcast a program by public health watchdog Ben Goldacre covering their history, which also features interviews with several big wigs involved in the studies, including the scientific director of Children of the 90s. It should be on iplayer here for a while.
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