Of all health studies that focus directly on human beings, those that follow participants from birth to death are among the most compelling. Their sheer unwieldiness — keeping track and making sense of entire messy, unpredictable lifetimes — is staggering.
Last month, Google X — the company’s research wing — announced the launch of just such a “longitudinal” study, branded its “most ambitious and difficult science project ever”. Working with researchers from Duke and Stanford Universities, the Baseline study will collect genetic and molecular data from thousands of individuals over the course of their lifetimes in an attempt to create the cellular-level “fingerprint” of a healthy human being.
This quest to understand health through lifetime studies underpins a huge area of research. It is a field in which the UK is a world leader, home to large-scale projects that began as far back as the 1940s, as well as recent studies such as the Millennium Cohort Study (MCS), begun in 2000. Data collected from the MCS ranges from surveys of children’s teachers — inquiring about children’s behaviour, learning and their parenting — to saliva tests for varicella zoster virus, Epstein-Barr virus, norovirus and adenovirus. Measures of height, weight, body fat, allergies, illnesses and cognitive ability will be taken at designated stages.
And also in the UK, the soon-to-begin Life Study is recruiting women and their partners who will be giving birth at Queen’s Hospital in the town of Romford, north-east of London, between 2014 and 2018. Further recruitment drives will follow in Leicester, in England’s East Midlands and Liverpool, north-west England. This “womb to tomb” study will be the first in the world to begin before children are even born. Following participants through adulthood and into old age, researchers will focus on how demographic and socioeconomic factors are linked to mental and physical health.
The longest-running British study is the National Survey of Health and Development (NSHD). Following 5,362 men and women since their birth in March 1946 the study is still yielding important results. When the NSHD began, food was still rationed and almost 50% of families didn’t have a bathroom. It was greeted with excitement and idealism, the participants hoping that they would be part of much-needed social reform. And from its very beginning, it had an impact: a very early finding in the 1940s was the revelation that just 20% of women surveyed had received any kind of pain relief during childbirth. The outcry triggered by this led to a change in regulations for the administration of anaesthesia.
While there was already consensus in the medical establishment that a child’s home environment had long-term effects on their health as adults, without studies such as the NSHD the nuances of this might have remained elusive. For instance, a 2013 analysis revealed that 60 to 64-year-olds who began life at the top of the socioeconomic spectrum performed 7 per cent — 20 per cent better in physical and cognitive tests (such as expiratory volume, handgrip strength and verbal memory score) than their less wealthy compatriots.
As the NSHD participants reach old age, it has become starkly obvious that, although an increase in standards of living can help, health never truly recovers from a poor start in life. Even participants’ chances of surviving until the age of 60 were influenced by childhood advantage or disadvantage. — © Guardian Newspapers Limited, 2014
