Avon Longitudinal Study of Parents and Children

Summary of cohort

The Avon Longitudinal Study of Parents and Children (ALSPAC), also known as Children of the 90s, is an ongoing birth cohort study of a sample of the population from Bristol and the surrounding area [91].

The main aim of ALSPAC is to understand how genetic and environmental factors influence the health and development of parents and children.

During initial recruitment all pregnant women who were resident in the former county of Avon, an area around Bristol in South West England, with an expected delivery date between 1^st April 1991 and 31^st December 1992 were invited to participate [91, 92]. ALSPAC initially enrolled a cohort of 14,541 pregnancies.

When the oldest children were approximately 7 years old, additional eligible participants were invited to join the study. Therefore, the total sample for the child-based data collected at 7 years is 15,589 with 14,901 alive at 1 year of age. All of these children have been regularly followed up using parental and self-completion questionnaires, medical records, educational and clinical assessment and through linkage.

A proportion of children born in the last six months of the recruitment phase (equivalent to 10% of the whole cohort) was selected to take part in a sub-study known as ‘Children in Focus’ (CiF). These children attended clinics between 4 months and 5 years of age (n=1432 ever attended).

In addition to studies of the children (termed Cohort G1), ALSPAC has also followed up the mothers (‘Focus on the Mothers’) and fathers (‘Focus on the Fathers’) of these children – the G0 Cohort – as well as the children of the Children of the 90s (Cohort G2).

During the COVID-19 pandemic, six computer-assisted web surveys were administered (April/May 2020, May/June 2020, Oct 2020, December 2020 – March 2021, July – Dec 2021, April/May 2022) to both G0 (parents) and G1 (original children) cohorts. Antibody tests were taken in October 2020 and serological measures were assessed in April – June 2021 and May – June 2022. 

Compared with the whole of Great Britain in 1991, the population of mothers with infants under one year of age resident in Avon were more likely to live in owner occupied accommodation, to have a car and less likely to have one or more persons per room and be non-white [93].

Similarly when comparing the ALSPAC participants to the whole eligible Avon population, less affluent people and ethnic minorities were less likely to be represented [93]. Ethical approval for the study was obtained from the ALSPAC Ethics and Law Committee and the Local Research Ethics Committees.