The Northern Ireland Longitudinal Study (NILS) BSPS Conference September 2007 David Marshall (NISRA)
PRESENTATION CONTENT 1. What is a Longitudinal Study? 2. What is the NILS? 3. Why does NI need an LS? 4. How Matching was completed 5. Security/Confidentiality 6. Projects
1. WHAT IS A LONGITUDINAL STUDY? A Study of the same group of people over time
Example | | | | | | | | | | | | | | | | | | | | | | | Census Birth of Child StillbirthDivorceMarriageCancer 27-year old Female in 1991 Death Address Change Birth of Child Address Change
2. WHAT IS THE NILS? Database of individuals and their life events that can be accessed (in a controlled way) by researchers Began work in 2003 Launched in December 2006 Funded by the Health Department in NI Steering Group
2. WHAT IS THE NILS? cont’d 104 NI birth dates (4 LS, 20 SLS) 2001 Census-based Main Data Sources Demographic Data from Health Registrations 2001 Census Births/Deaths Registrations Property Valuations
E&W LS SLSNILS Number Dates Size500,000(1%)300,000(5%)500,000(28%) Start Date Number of Censuses 421 Data on all 3 LSs Births to sample mothers Births of sample members Deaths of sample members Immigrants Embarkations Widow(er)hoods
E&W LS SLSNILS Births to Sample Fathers ✔ Stillbirths/ Infant Deaths ✔✔ Internal Migration ✔ Cancer Registrations ✔✔ Hospital Episodes ✔ Education✔ Marriages✔✔ Claimant Count ✔
2. NILS Mortality Dataset Additional exercise All deaths post 2001 linked to Census 65,000 deaths linked Population at risk is 2001 Census Compared to 20,000 in NILS main sample Many of death-based analyses will probably be carried out on this until further information included in NILS
3. WHY DOES NI NEED AN LS? Different People Different issues Different Policies
4. HOW MATCHING WAS PROCESSED Data Preparation Automatic Matching & scoring Exact Matching Exact Matching ‘Fuzzy’ Matching ‘Fuzzy’ Matching Manual Confirmation Confirmation Searching Searching
4. MATCHING LEVELS Approximately : 50% of matches were exact 30% very good fuzzy matches 10% manual confirmation on fuzzy matches 10% Manual searches of database 87.4% unadjusted match rate 96.4% adjusted for Census imputation, accuracy of health service records for Census imputation, accuracy of health service records
5. SECURITY/CONFIDENTIALITY Processed Under Census Legislation Personal Data & Sensitive Personal Data Research Approvals Group and application process Researchers only allowed access to anonymised records Data Held in Secure Environment Closed network Biometric access to PCs No output media allowed (CDs, Data Sticks, Print-outs) All output checked for Disclosure
6. NILS Projects Temperature-related mortality and housing Religion / denomination differences in mortality Impact of non-linkage using NILS mortality
Some test findings so far…. Migration ‘Stickiness’ Cultural and educational variables in fertility analyses important Carers have lower mortality Mortality Rates by Religion Suicide risk is strongly related socio- economic disadvantage and social support at an individual level & area factors have no independent effect
6. ESRC/RDO Money for Researchers £300,000 for short research projects to raise awareness of NILS Application Process (2 stage)
SUMMARY 28% Sample of NI Population Includes 2001 Census, birth/death and heath service registration data Data held securely within legislative boundaries Projects started and first paper accepted in academic journal
The Northern Ireland Longitudinal Study (NILS) BSPS Conference September 2007 David Marshall (NISRA)
The Northern Ireland Longitudinal Study (NILS)
Contextual DataNILS Core DataEvents Central Services Agency Key demographic information on NILS members (514,000 Census Date New members (36,000) 2001 Census Database 1991 Census Births Data (baby linked to Birth Registration) 2001 births onwards Babies linked to Birth Reg. Pre 2001 Deaths Births to MothersBirths to Fathers Stillbirths & Infant Deaths Migration (Immigrants, Emigrants, Re-Entrants & Within NI Movers) VLA/Rating Data POINTER Address Database