Northern Ireland Longitudinal Study (NILS)

Northern Ireland Longitudinal Study microdata are available resources for a variety of research studies

The NILS is proportionally the largest longitudinal study in the UK covering an impressive 28% of the Northern Ireland population and accounting for approximately 50% of Northern Ireland households. The NILS ‘core’ data are drawn from the Health Card Registration data and then linked to data from Census returns (1981, 1991, 2001 & 2011), Vital Events (births, deaths and marriages), Migration and Property data. The result is over 30 years of longitudinal data which is regularly being updated. In addition to this rich resource there is the potential to link further Health and Social Care data via Distinct Linkage Projects as well as the option of using the Northern Ireland Mortality Study (NIMS) for more detailed investigation into NI mortality patterns. 

The NILS and NIMS microdata are invaluable resources for a variety of research studies, focussing on a range of topics such as mental health, migration, commuting and working patterns. To find out more, please consult the NILS-RSU website or the NILS Annual Report.

NILS structure


Useful NILS Documentation

Please consider the following policies and procedures documentation before continuing with your application: 

See the NILS metadata for information on the NILS variables, sample structure, and sample membership

The NILS project modification form can be completed and submitted to RSU during the analysis phase if the research team identify the need for minor adjustments to timeframes, data, and research team members. This form can also be used to request the project be de-archived

Univariate Synthetic Data

NILS Univariate Synthetic data can now be requested to facilitate remote writing of code without needing access to the real data and the secure room.  Please note that timescales for producing the univariate synthetic data may vary according to resources and volume of requests.

Research Approvals Group

NILS projects will be considered by the Research Approvals Group (RAG), and are only approved when the following conditions are met:

  1. that there is a longitudinal aspect to the research;
  2. that the project relates to Health and Social Care research;
  3. that the project supports the development/delivery of public policy

For more details please see the NILS RAG criteria.

Dates of NILS RAG:

Application deadline: 15 April 2021 | NILS RAG: 29 April 2021

Application deadline: 25 May 2021 | NILS RAG: 8 June 2021

Application deadline: 27 July 2021 | NILS RAG: 10 August 2021

Application deadline: 28 September 2021 | NILS RAG: 12 October 2021

Application deadline: 30 November 2021 | NILS RAG: 14 December 2021

Please bear in mind that the application deadline is the date at which the final version of the application (following feedback from RSU) should be submitted to RSU. 

Time frame

NILS projects normally take 2 to 4 months from application submission to dataset creation. NILS DLPs can take six to eight months, with more complex linkages taking longer.

Ethics for NILS Projects

The NILS database has ethical approval from ORECNI. However, if the potential project intends to link health data to the NILS database, further ethical approval is required. This ethical approval must be applied for by the research team. Further information can be obtained through the ORECNI website

Apply for a NILS Project

To apply for a NILS project click the link and follow the instructions: 

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