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The Northern Ireland Longitudinal Study |
The Northern Ireland Longitudinal Study
The
Northern Ireland Longitudinal Study (NILS) is a large-scale data linkage study which has been created
by linking individual level administrative and statistical data. Information is linked over time on people
from Census, vital events (births, deaths and marriages) and health registration datasets.
The NILS is managed by the Northern Ireland Statistics and Research Agency (NISRA) and is jointly funded by
the Department of Health, Social Services and Public Safety (DHSSPS) and the Research and Development
Office (RDO).
The NILS consists of an approximate 28% (c. 500,000) sample of people in Northern Ireland.
Sample members are chosen on having one of 104 birth dates, four of which coincide
with the England and Wales Longitudinal Study.
To date, information held on sample members includes:
- 2001 Census information on the sample members and people living with them;
- General Register Office (GRO) information on the death of a NILS member;
- GRO information on the birth of NILS members from 1997 onwards;
- GRO information on birth events to NILS members;
- GRO information on stillbirth and infant deaths to NILS members;
- Widow/erhood events to NILS members;
- Marriage event information from 2004 onwards;
- Immigration, emigration, re-entry and internal migration events using health
registration data downloaded every six months.
What can the NILS tell you?
The NILS includes a range of variables which can be explored, including cultural, demographic, economic,
health, housing and social issues. Using the example of health, the potential uses of longitudinal
studies such as the NILS are considerable. With the inclusion of socio-demographic data from census
and other sources, an added dimension can be brought to the analysis of health variations and inequalities.
Social differentials in health and mortality can be explored using such measures as the Registrar General’s
social class, deprivation indices, NSSEC, occupation and industry, housing tenure, car access, overcrowding
and lack of amenities in housing, ethnicity and sex.
Change over time can be looked at with reference to a person’s later health or their cause of death because
of the linkage of data at different time points.
The effects of geography and migration can also be examined using the demographic information taken from
the six monthly downloads of health registration data.
The England and Wales LS, which this dataset is modelled upon, has been used to
look at a range of important questions including: occupational mortality, fertility changes,
family reconstitution, women’s occupations, geographical and social inequalities in health,
social mobility, ethnic health etc. Types of analyses include:
- Prospective analysis of census and event data. For example: studies of associations between
employment status and mortality, between economic status and cancer registrations, or between
socio-economic factors and fertility; survival analysis of mortality by area deprivation.
- Prospective analysis of successive event data. For example, studies of changes in birth spacing, associations
between fertility and cancer survival.
- Cross-sectional analysis. Especially for studies of ethnic or geographical factors.
- International comparisons. Countries such as France, Denmark, Finland and the USA have similar programmes to the
LS and hence the NILS.
Much of the work done using this database in England and Wales has fed into government social policy, particularly into
the health targets defined by the Department of Health.
How can the NILS be used?
The NILS is a sensitive dataset. Micro-data files are not externally available to users. Instead, the NILS micro-data
can only be accessed and analysed within a ´safe setting´ in NISRA headquarters. All released information is anonymised
and aggregated to prevent the identification of any individuals.
To use the NILS data a formal application must be made and approved by the NILS Research Approvals Group (RAG).
A step-by-step guide to accessing the NILS data is given on the NILS web site,
www.nisra.gov.uk/nils. The NILS team provide advice on the suitability of the NILS dataset being used in potential research projects
as well as providing a research support function for approved projects. Contact details are available from the web site.
What resources are available?
The
Northern Ireland Longitudinal Study Research Support Unit
(NILS-RSU) was launched on 4 June 2009 to promote the research potential of the data and provide expert support
services to researchers from both the academic and government sectors. Resources include details on all available
NILS data, a data dictionary and, application guide.
What data are available?
2001 Census data
Census information on NILS members and other members of their household, including data on:
Age, sex and marital status
Family, household or communal establishment type
Housing, including tenure, rooms and amenities
Country of birth
Ethnicity
Educational qualifications
Economic activity
Occupation and social class
Migration
Long-standing illness
Self-rated health
Religion
Care giving
Vital Events (GRO Data)
New births into the sample
Births to sample mothers
Births to sample fathers
Stillbirths to sample mothers
Stillbirths to sample fathers
Infant mortality of children of sample mothers
Infant mortality of children of sample fathers
Deaths of sample members
Widow(er)hoods of sample members
Marriage events of sample members (2004 onwards)
Migration Events (Health Registration Data)
Immigrants into the sample
Emigration out of Northern Ireland of sample members
Re-entries into Northern Ireland after previous emigrations of sample members
Migration within Northern Ireland of sample members
Other Data
Valuation and Lands Agency (VLA) Data – Information on properties including information on number of
rooms, property type, central heating etc. Also included are the capital valuations for the
properties used in the 2005 Rating reform.
Area based data – taken from the NI Neighbourhood Statistics portal, www.ninis.nisra.gov.uk/.