Growing Up in New Zealand

1. Growing Up in New Zealand Data Linkage Peter Tricker, Data and Systems Manager

2. Overview of presentation • Introduction to Cohort • Recruitment • Characteristics • Longitudinal Research Questions • Domains and Themes • Data Collections • Data Linkage • Data Merge • Questions

3. Recruitment for Growing Up in New Zealand • Recruited in third trimester of pregnancy. • EDD between April 2009 and March 2010. • Residing in one of three district health boards stretching from central Auckland to the central North Island. • Main Cohort • 6,822 mothers • 4,404 fathers • 6,919 children

4. Cohort Characteristics • The cohort broadly is generalisable to all current NZ births, in particular to ensure statistical power to Māori, Pacific and Asian populations – something not achieved in earlier New Zealand longitudinal studies

5. Longitudinal Research Questions The overall objective of the study is to provide a robust, relevant evidence base to inform policy across sectors related to children and their families in 21st century New Zealand. Overarching Longitudinal Research Questions: • What determines developmental trajectories across multiple levels of influence throughout the life course? • How are New Zealand children faring developmentally across multiple domains at discrete points in the life course? • How are these developmental trajectories and outcomes associated with ethnicity across the life course? • What factors and trajectories, particularly across multiple levels of influence, confer resilience and optimise development for our New Zealand children?

6. Research domains and themes for Growing Up in New Zealand

7. Data Collections • Telephone interviews also planned for 31 months and 39 months primarily for retention purposes, though some data will be collected along with the household grid. • Full face-to-face pre-school interview (4 years)

8. Data Linkage • 97.5% of mothers consented to perinatal data and routine health data collection for first year of their child’s life. • Sources are: Perinatal Data • District Health Boards (DHBs) within catchment area. • Private cooperatives who look after lead maternity carers (usually midwives). Routine Health Data • Ministry of Health.

9. Data Collection – Approval Process • Each district health board, midwifery organisation and the Ministry of Health approached separately. • Must provide proof of ethics committee approval. • Must be able to prove that the requested data is for consented participants. • i.e. must produce a copy of the signed consent form.

10. Data Linkage – NHI number • National Health Index number (NHI) • Required to identify individuals in the health system and to collect health data. • Anyone who has been to a health professional will have one. • NHI obtained from the Ministry of Health • Growing Up provides nominal information: • First names, last name, DOB, sex, residential address • Ministry of Health carries out up to three matching exercises • Automatic match • Manual match • Investigation • End result for Growing Up: 99.92% match

11. District Health Boards – Perinatal Data • A master list of perinatal data variables was developed during the pilot study based on data from Auckland DHB. • No requirement in New Zealand for district health boards to collect data in a standard way. • Patient management systems not necessarily centralised in each DHB. • DHBs do not capture perinatal data from private clinics or via independent midwives. • In Waikato some of the regional hospitals did not store their data electronically (had to be collected in person). • To make the requests mothers were identified using their NHI and delivery dates. • DHBs sent back matching child NHI to ensure we had the right record.

12. Perinatal Data Collection • Mothers reported at 6 week call where they gave birth. • Name of hospital or clinic, home birth, overseas, etc. • These responses were used to decide how to group requests for each DHB or independent midwifery organisation. • Not always accurate since patients can be transferred during labour. • Often requests were made to several DHBs for the same information to see who had the data.

13. Ministry of Health Data • Data collections • Mortality. • National Immunisation Register. • National Minimum Dataset (hospitalisations). • Child NHI was the only requirement for the Ministry of Health to make a match against their records.

14. Data Linkage with Participant Data Set • Match merge linkage used. • Most effort spent on validating the perinatal data sets from each of the DHBs and private organisations. • For example • No duplicates. • No records that are not part of Growing Up in New Zealand. • Correct mother/child combination. • Correct child (and not a sibling for example). • Validation of child DOB and sex against Growing Up in New Zealand data set. Recorded ethnicity generally not used to validate the data as it tends not to be accurate.

15. Next steps • Perinatal data sets will be merged into one file based on a common set of variables and then linked to the study data set. • Ministry of Health data not so problematic as it is from one source. It is in the process of being linked.

16. Questions