Study sample

The LSAC study is using an accelerated cross-sequential design in which 2 cohorts of children are being followed for over 20 years, starting from when the children were aged 0-1 year in one cohort and 4-5 years in the other cohort.

The study is made up of 10,000 young people which are split into 2 groups or ‘cohorts’. The 'Baby', or 'B' group was aged 0 to 1 year old and the 'Kinder', or 'K' cohort was aged 4 to 5 years old.

The sample of 10,000 children was selected from the Medicare enrolment database (formerly the Health Insurance Commission).

Participant recruitment

In Wave 1, the Health Insurance Commission selected a sample of more than 18,500 children within a set of birth dates from the Medicare administrative database. First, a sample of children was drawn via a random selection of 311 postcodes.

Children of the appropriate ages were sent an 'invitation to participate' letter to the Medicare cardholder, along with a brochure on Growing Up in Australia. Families had 4 weeks to register their withdrawal from the study.

Interviewers then contacted families who had not withdrawn to arrange an appointment for their first interview. The study has contacted participating families every 2 years since to conduct interviews (with exceptions due to COVID-19). Participants in the study have included the study child/young person, as well as their parents, carers and teachers.

Participant retention

All Wave 1 participants (N= 10,090)  were invited to participant in subsequent waves, but not all participants completed the survey due to withdrawal or other reasons. The response rates of families for subsequent waves were:

• Wave 2 – 89.9% (n = 9,070)
• Wave 3 – 86.4.% (n=8,717)
• Wave 4 –83.4% (n=8,411)
• Wave 5 – 79.7% (n =8,041)
• Wave 6 – 72.4% (n=7,301 )
• Wave 7 – 64.1% (n=6,470)
• Wave 8 – 61.1% (n=6,164)
• Wave 9C1 – 37.7% (n=3,806)
• Wave 9C2 – 51.1% (n=5,151)
• Wave 10 – 47.9% (n=4,833).

Data collection

To date, 10 waves of data have been collected using a mix of:

• cognitive and or physical testing
• questionnaires
• in-person interviews.

The next data collection, Wave 11, is underway. Data were collected in: