The Northern Ireland
Longitudinal Study (NILS)
BSPS Conference
September 2007
David Marshall (NISRA)
PRESENTATION CONTENT
1.
2.
3.
4.
5.
6.
What is a Longitudinal Study?
What is the NILS?
Why does NI need an LS?
How Matching was completed
Security/Confidentiality
Projects
1. WHAT IS A LONGITUDINAL
STUDY?

A Study of the same group of people over time
Example
27-year old Female in 1991
Address
Change
Address
Change
Marriage
Birth
of
Child
Census
| |
1991
Stillbirth
|
|
|
|
Birth
of
Child
|
|
|
Divorce
Cancer
Census
|
| |
2001
Death
Census
|
|
|
|
|
|
|
|
| |
2011
|
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
Number
Dates
Size
Start Date
Number of
Censuses
Data on
all 3 LSs
E&W LS
SLS
NILS
4
20
104
500,000
(1%)
1971
4
300,000
(5%)
1991
2
500,000
(28%)
2001
1
Births to sample mothers
Births of sample members
Deaths of sample members
Immigrants
Embarkations
Widow(er)hoods
E&W LS
Births to Sample Fathers
Stillbirths/ Infant Deaths
Internal Migration
Cancer Registrations
Hospital Episodes
Education
Marriages
Claimant Count
SLS
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
NILS
✔
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
‘Fuzzy’ Matching
Manual

•
•
Confirmation
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
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 socioeconomic disadvantage and social support at
an individual level & area factors have no
independent effect
6. ESRC/RDO Money for
Researchers
 £300,000
 to
for short research projects
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)
nils.nisra@dfpni.gov.uk
www.nisra.gov.uk/nils
Contextual Data
2001
Census
Database
1991 Census
Babies linked to
Birth Reg. Pre 2001
NILS Core Data
Events
Deaths
Central
Services
Agency
Key demographic
information on NILS
members
(514,000 live)
Births to Mothers
Births to Fathers
Stillbirths &
Infant Deaths
@ Census Date
Births Data
(baby linked to
Birth Registration)
2001 births onwards
VLA/Rating Data
New members
(36,000)
POINTER
Address Database
Migration
(Immigrants,
Emigrants,
Re-Entrants
& Within NI Movers)