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A total of 34 cohorts were included in the review, encompassing 19 cohorts partially or fully funded by the MRC and 15 cohorts funded entirely by others. These cohort studies comprise the majority of large longitudinal population studies in the UK. The combined annual spend supporting the 34 cohort studies is £27.6m, with MRC funding accounting for £9.6m of the total. In addition, two new large population cohorts, one of which is funded in part by the MRC, will commence in 2014. A key feature of the UK portfolio is the large number of cohorts that have been followed for a long period of time, with half of the cohorts (n=17) having been followed for at least 20 years. One of the oldest cohorts in the portfolio is the MRC National Survey of Health and Development/1946 Birth Cohort, which is the oldest cohort continuously followed from birth in the world. On average, one new large population cohort has been funded every year since 1990. The age range of the UK cohort portfolio spans the whole life course from birth to over 100 years old, with the
Southampton Women’s Survey uniquely collecting data on mothers before they conceived. Four of the 34 cohort studies include women only and one study is exclusively male. The current size of the cohorts ranges from 1.24 million in the Million Women Study to approximately 150 in CFAS I (of the original 18,500 who were over 65 years of age at the time of recruitment). The Million Women Study and UK
Biobank together account for three quarters of the total participants in the portfolio. It is estimated that 2.5 million people in the UK have been recruited to large population cohort studies and today there are over 2.2 million people, which is 3.5% of the UK population, who are still taking part.
Twenty-eight of the total 34 cohorts in this review were included in an exercise modelling the current and projected profile of the UK cohort portfolio in the next 10 years. Currently, broadly equal numbers of men and women are being studied up to age 20 years, but thereafter the number of women exceeds that of men at all ages. Far greater numbers of women than men are being studied at ages over 50 years, but there are also fewer men between the ages of 20 and 40 years. The Million Women Study largely accounts for the disparity in the numbers of men and women being studied. UK Biobank is also a particularly large study and contributes to the large numbers observed at ages 45-74 years for both men and women.
Extrapolation of data from the 28 cohorts forward over ten years, allowing for attrition, and including estimated numbers for the two newly planned cohorts (the Life Study and NICOLA) showed that in 2022 most of the cohort participants will be within the 55-85 year age range. Unsurprisingly, the number of women studied still greatly exceeds that of men in later life. The Life Study which commences in 2014 will bring in a large number of children of both sexes.
It will also collect data on the children’s fathers which will boost the low number of men in the 30-50 year age range.