The Millennium Cohort Study (MCS) is following the lives of 19,517 children born across England, Scotland, Wales and Northern Ireland in 2000-01.
A renewed interest in child wellbeing in the late 1990s in the UK set the scene for a new and distinctive child cohort study, after a gap of 30 years.
Since the initial birth survey the cohort has been followed up five times at ages 3, 5, 7, 11 and most recently at 14, when 11,872 cohort members (11,726 families) took part. The next survey will take place in 2018 when the cohort members are age 17.
The main data collection methods used during the study have included questionnaires, cognitive assessments, and interviewer-administered physical measurements.
Questionnaires have been used to gather a variety of information about study members and their families, including social and family background, mental health and wellbeing, and housing, employment and income.
Cognitive assessments have measured verbal, language and numeric ability throughout childhood.
Physical measurements and self-reported health have provided information about different health conditions experienced by the study members. Cohort members have been asked to wear an activity monitor and complete a time use record to measure daily activity. The study has also collected saliva samples from study members and their biological parents to see how their health is linked to their genes.
MCS has provided important evidence to show how circumstances in the early stages of life can influence later health and development.
Findings from the study have revealed that children who are breastfed tend to be healthier and to show better cognitive development.
MCS has also found that the month children are born could influence which classes or sets they are in. Researchers showed that children born in the summer months were more likely to be placed in lower ability groups than their autumn-born peers.
MCS is fourth in a long line of cohort studies in the UK, but is distinguished from them in a number of ways related to the design of the sample. Its carefully constructed sample (19,517 children in 19,243 families selected through Child Benefit Records) was designed to provide a proper representation of the total population.
Its first sweep, carried out during 2001-2002, laid the foundations for a major new longitudinal research resource, taking a new “year long” cohort of around 19,000 babies.
In England and Wales they were born over the 12 months starting in September 2000, and over 13½ months from late November 2000 in Scotland and Northern Ireland. As the MCS children were born between September 2000 and January 2002 the study is also well-placed to identify any season-of-birth effect on children’s development.
Information was first collected from parents when the babies were aged 9 months.
The sample design allowed for disproportionate representation of families living in areas of child poverty, and in areas of England with high ethnic minority populations.
Certain sub-groups were intentionally over-sampled, in particular those living in disadvantaged circumstances, children from minority ethnic backgrounds (in England), and youngsters growing up in the smaller countries of the UK, namely Scotland, Wales and Northern Ireland.
Individual pupil information from the National Pupil Database has been linked to survey data, for those cohort members whose parents consented. This data is available for use from the Secure Data Service.
Management and funding
Accessing the data
The majority of MCS survey data can be accessed by bona fide researchers through the UK Data Service at the University of Essex. Anyone wishing to access the data will need to register with the UK Data Service before downloading. Some datasets are only available via Special Licence, or via the UK Data Service Secure Lab. Access arrangements comply with ESRC Research Data Policy.
Research metadata, including basic frequencies, is available using NESSTAR at the UK Data Service. The (CLS) website provides copies of the questionnaires and documentation used in the study. The CLS data dictionary offers further metadata including variables and frequencies.
Roxanne Connelly, Lucinda Platt; Cohort Profile: UK Millennium Cohort Study (MCS). Int J Epidemiol 2014; 43 (6): 1719-1725. doi: 10.1093/ije/dyu001