Cohort Profile: The Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA)

The Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA) is Northern Ireland’s largest health and social care cohort collecting longitudinal data from a representative sample of the over-50s population. 8283 participants aged ≥50 years and living in private residential accommodation were recruited, from a randomized, stratified sample of Northern Ireland addresses, to the Wave 1 cohort between December 2013 and March 2016. A follow-up (Wave 2) of the cohort took place between May 2017 and November 2019, with a response rate of 73% (n = 6152). NICOLA participants will undertake a detailed survey, in their own home, every 2 years with a detailed health assessment every 4 years. The NICOLA data set comprises a diverse range of objective and subjective measures of physical and mental health, life expectancy, disability, education, economic activity, social participation and support, household and family structures; and uniquely to NICOLA, the effects of ‘the Troubles’, a detailed ophthalmological assessment and a dietary assessment. Inclusion of unique measures allows analysis of the social and contextual influences on the distribution of health status determinants particular to Northern Ireland. The collection of data via subjective reporting in interviews and self-completion methodologies combined with objective measurement of health and wellbeing allows detailed analysis of the ageing profiles. The NICOLA cohort is flagged on the National Health Applications Infrastructure Service to enable robust and comprehensive linkage for identification of participant outcomes and affecting factors. The harmonization of health status measures with other ageing cohorts allows cross cohort comparative analysis, those of particular relevance being the English Longitudinal Study of Ageing (England) and The Irish Longitudinal Study of Ageing (Republic of Ireland). Comparability of NICOLA to other ageing studies will also be enabled via the Gateway to Global Aging Data (G2G) and with NICOLA data being archived within the Dementias Platform UK (https://www.dementiasplatform.uk/research-hub/data-portal). Access to the anonymized data is by direct application to the NICOLA study (https://nicola.qub.ac.uk/sites/NICOLA/InformationforResearchers/#requesting-access-to-nicola-data-or-biological-samples-910951-1). Although a region of the UK previously known for having a younger population, Northern Ireland (NI) is experiencing a similar demographic transition that is seeing life expectancy continuing to rise. Government population projections1 indicate that by 2028 39% of the population will be ≥50 years of age, with this statistic rising to 43% by 2048. This increase in the ageing population presents challenges, particularly for policy makers wishing to support citizens through the equitable provision of health and social care services and wider economic policies. NICOLA closely follows the comprehensive approaches taken by the English Longitudinal Study of Ageing (ELSA)2, established in 2002, and the Republic of Ireland’s Irish Longitudinal Study on Ageing (TILDA)3 established in 2009. These, and other international longitudinal cohort studies of ageing, can yield much that could be useful to policy makers. However, NI has a unique social history, relating specifically to political and social unrest, justifying closer scrutiny in a local cohort. To reflect this, NICOLA has particular focus on intergenerational poverty, transition points in ageing and the effects of diet on the ageing process. The study also includes questions of unique relevance to ‘the Troubles’—a time of political violence in NI between the late 1960s and the late 1990s, and its consequences for the ageing NI population. NICOLA is supported through a portfolio of funders that recognized the need for a Northern Irish ageing cohort. The Atlantic Philanthropies (AP) indicated its early support for the cohort and shortly thereafter the Northern Ireland Executive Office committed funding for the NICOLA pilot study in 2012. Following the successful pilot, the UK Clinical Research Collaboration (UKCRC), the Economic and Social Research Council, the Centre for Ageing Research and Development in Ireland (CARDI) and the Northern Ireland Public Health Agency Research and Development office (HSC R&D) added to the AP funding to ensure a successful launch of NICOLA. NICOLA is based within the Centre for Public Health, Queen’s University Belfast, with a Stakeholder Council with representation from: the Northern Ireland Executive Office, the devolved Northern Ireland government department, within the Northern Ireland Executive; a range of Executive Agencies including the Department for Communities and Department for the Economy; the local Health and Social Care (HSC) infrastructure; the Institute of Public Health Ireland and The Irish Longitudinal Study of Ageing (TILDA). As with other cohorts, NICOLA focuses on the various aspects of the ageing process and how they interact. To this purpose, the involvement of expertise from medical and health sciences, economics and management, social sciences and psychology within NICOLA aims to maximize the advantage of multidisciplinary research, both within Queen’s University Belfast and through extensive collaboration with international research groups. NICOLA is closely affiliated to the Administrative Data Research Centre Northern Ireland (ADRC-NI)4 and will maximize the cohort data through ethically approved linkages to available administrative data sets. Data linkage will include, in the first instance, linking the NICOLA data to routinely collected health and social care data from the Business Service Organisation (BSO) Honest Broker Service (HBS)5 and also linkage with the Northern Ireland Cancer Registry6. Examples of such data include hospital admissions, general practitioner and dental records, health screening registers and disease registers. NICOLA is a longitudinal panel of 8283 participants representative of an ‘eligible population’ defined as community dwelling adults aged ≥50 years living in private households in NI, broadly equivalent in sample size to both TILDA3 and ELSA2. Those living in residential care homes or other institutionalized settings, e.g. nursing homes, or who lacked the capacity to provide informed consent were not eligible to participate. Spouses or partners of eligible participants who shared the same residency were also invited to participate, regardless of their age. The spouse or partner completed the same assessments. The purpose of including the spouse or partner was to obtain overall household-level information including, for example, finances and household structure. Other members of the household were not included. A total of 195 who were aged <50 years chose to participate, resulting in a total of 8478 participants in NICOLA Wave 1. The BSO General Practitioner Register Database was used as the source for identifying addresses containing eligible individuals. The sample was ordered using geographic stratification, identified addresses ordered within postcode geography and then a fixed interval (systematic) sample drawn. The sample was merged with the Pointer Database of addresses for NI maintained by Land and Property Services providing a common standard address for every property, enabling the full range of address information to be available for fieldwork interviewers to plan their schedule of work. All individuals living at each address were included in the sample. NICOLA required a total of 12 077 addresses (main sample) and in addition a 20% sample contingency of 2415 addresses (reserve sample), resulting in a total of 14 492 addresses in the initial sampling frame. Both the main and reserve samples were extracted at the start of the project. In a final addition, a further sample of 2416 addresses (additional reserve) were extracted from BSO in the later stages of Wave 1 fieldwork to enable the target cohort number to be achieved. The purpose of the reserve samples was to compensate for potentially lower-than-expected response rates to the initial study invitation. In total, 16 908 households received an invitation letter to take part in Wave 1. To be eligible to take part in NICOLA, individuals must be aged ≥50 years and therefore born on or before 30 September 1962. All individuals aged ≥50 years enumerated in respondent sample households (n = 16 908 households) were invited to become part of the longitudinal sample. An introductory letter was sent to the household (unnamed—householder only rather than a specific individual). The household was then visited by an Ipsos MORI fieldworker who obtained the name and informed consent from eligible participants. Individuals not yet 50 years of age, who were institutionalized or who lacked the capacity to provide informed consent were excluded from joining NICOLA. The NICOLA study was designed to follow similar sampling protocols to those used in TILDA3 and ELSA2, thus facilitating comparative analysis. As with ELSA and TILDA, participants were selected according to a community home address rather than a nursing or residential home. In addition, the governance implications of accessing individuals in institutionalized care was considered to be too challenging in terms of time, resources and impact on overall recruitment rates. The general health status of many individuals in care settings may also have affected their ability to both consent and participate in the computer-assisted personal interview (CAPI) and health assessment. Based on this, it was decided to only recruit individuals living in the community. Partners of eligible participants did not have to have been born before 30 September 1962 but had to be living at the same address as the selected age-eligible participant. As part of the written consent process, participants were asked whether they agreed to future contact by the NICOLA study team. It is the expectation that, within future waves, participants will be followed up for admission into residential institutions, depending on ethical approval. NICOLA aims to collect data from all participants within structured waves of ∼2-year intervals. The proposed design of Wave 3 (pending funding) will include a home-based health assessment, CAPI and self-completion questionnaire (SCQ) with a focus on the following research topics: immune response, the microbiome, digital inclusion, food insecurity, cognitive health and eye health. With continued follow-up, all NICOLA participants will be invited to take part in a CAPI every 2 years and a detailed health assessment every ∼4 years. The use of the SCQ is intended as an adjunct within each wave. It is the intention that participants will be followed up for a period of ≥10 years. The Central Survey Unit of the Northern Ireland Statistics and Research Agency (NISRA)7 was commissioned by the NICOLA project team to conduct an initial pilot of the CAPI on 197 addresses. Of these 197, 186 addresses were eligible (i.e. one household member living at the address was aged ≥50 years) and, of these, 89 households consented to participate (n = 153 participants), thus representing a 48% household response rate. The pilot study was conducted between October and November 2013. The main survey was informed by this short pilot study with a revised format, content and length, CAPI questionnaire and supplementary SCQ utilized in Wave 1 NICOLA fieldwork (see Table 1). Summary of data collected in NICOLAa Wave 1 and Wave 2 NICOLA, Northern Ireland Cohort for the Longitudinal Study of Ageing. Self-completion questionnaire. Completed as part of Wave 2 computer-assisted personal interview. Dietary self-completion questionnaire. Summary of data collected in NICOLAa Wave 1 and Wave 2 NICOLA, Northern Ireland Cohort for the Longitudinal Study of Ageing. Self-completion questionnaire. Completed as part of Wave 2 computer-assisted personal interview. Dietary self-completion questionnaire. Wave 1 also includes a wide-ranging health assessment module conducted by trained registered nurses in the Wellcome Trust–Wolfson Northern Ireland Clinical Research Facility (NICRF) located in Belfast or, when necessary, in the participant’s home (see Table 1). Biological samples including a non-fasting blood and urine sample were collected from participants as part of the health assessment. All samples were initially processed in the within 4 of the were short in the within the and then to the main in the Centre for Public Health at Queen’s University Belfast on a All samples were to the main in an containing In the of home a was used for samples from the participant’s home to the main for All were then in analysis. were for dietary and were available international with samples included in every All were using the with the of and were using the status was using the The health were conducted between and the CAPI interviews were completed between December 2013 and March 2016. The time between the CAPI interview and health assessment was the used in the health assessment and the from the health assessment will be in a from the health assessment also available in the NICOLA health assessment can be via NICOLA Wave 1 included within its study The first of these to the of of invitation letter on the to the of the of when the SCQ was to the participant on their and the invitation letter of the sample households invited to take part in NICOLA were to 1 of 12 of the invitation The was to whether the of the the of NICOLA as a or a and the or of a of within the of the letter affected in study In the SCQ participants were to the questionnaire at the of their home interview or to The was to the impact of the at the participant was a questionnaire on rates. of the in the SCQ was (i.e. at the of the home interview or by the participant then completed the SCQ in their own time and it to the NICOLA research office using a analysis and reporting of both will follow in Of the 16 908 households who received the invitation letter to take part in Wave households agreed to participate. these a total of 8478 CAPI interviews were conducted with eligible participants between December 2013 and (see 1). for NICOLA Wave 1. NICOLA, Northern Ireland Cohort for the Longitudinal Study of computer-assisted personal interview. as aged ≥50 years living in private residential accommodation in Northern Ireland Of the 8478 CAPI interviews 195 were with partners of eligible participants who were not yet 50 years of at the time of interview. of CAPI participants a Table 2 the of those participants who completed the CAPI and SCQ of the of NICOLA Wave 1 total SCQ and samples and with Northern Ireland population aged ≥50 NICOLA, Northern Ireland Cohort for the Longitudinal Study of computer-assisted personal self-completion questionnaire. for Northern Ireland population aged ≥50 years based on NI May = or = or = postcode for with to to in the of NICOLA Wave 1 total SCQ and samples and with Northern Ireland population aged ≥50 NICOLA, Northern Ireland Cohort for the Longitudinal Study of computer-assisted personal self-completion questionnaire. for Northern Ireland population aged ≥50 years based on NI May = or = or = postcode for with to to in the was a of in the CAPI sample than of the sample were aged with of the sample in the to and aged years. of participants were or for for were or for for A of the sample living of the sample had at education, with having a A of the sample were or in The addresses were than of the participants in an (i.e. or within a were from and were from Belfast the of those participants who consented and took part in the CAPI but did not an SCQ those who (see Table the following was the total sample and for and they were to be in the to to be or to be living with to have to be and to be living in an the total and The first from NICOLA Wave CAPI was in November This on the following topics: social and and physical health, and the of the NICOLA of the from the The of in the sample with age. of the sample were and had been with of aged years were of the sample and this to for those aged years. was as in the with the and as in with of participants having a living and were in the (i.e. having both at one living and one living of those with were in the is than those with A of participants that they were for or of or relating to age. that they had one to on they of were as as to being in the of were to be home As health was with a of being in for those aged years. was also the of of being in with of in those aged years. This was for participants. of those reporting being in were This was particularly the for aged years. Of those participants aged years and 48% were were of and the home and of participants having a The of and in of living and of living with age. rates than of and rates of or mental health. all measures of health, or participants with those reporting they were or the health. All health measures a in the health between the and was the health of those living in the was points than those in the or than of participants that they had visited their general practitioner at in the use of hospital services and the was of care services with age. Those living in of the social with the had the use of each Those with the use also health, with had a Wave 2 of the NICOLA study was conducted between May 2017 and November All living participants who took part in Wave 1 were sent a letter to take Wave 2 of a were also invited to a The questions in the CAPI and SCQ were based on the questions asked in Wave 1 with the addition of and questions as in Table 1. Following the CAPI participants were an SCQ including a for the SCQ Wave was health assessment at Wave Although every was to a interview with the were participants in Wave 2 who were to participate in the CAPI in to a physical or cognitive and therefore a interview was with a family interviews were only into the study at Wave 2 and were not conducted in Wave 1. interviews or of a NICOLA participant who had in Wave were also into the study at Wave A of the NICOLA sample is being conducted as a final part of Wave 2 with the to recruit participants the A further to Wave 2 has been the of a SCQ with the This specific questionnaire was designed to information relating to physical and mental health, food and and health and social and the period of The questionnaire content is closely with that of ELSA and other cohorts to the UK Longitudinal Collaboration to comparative analysis. The data obtained will enable to and as as UK in to the impact of on the health and wellbeing of Of the (n = Wave 1 participants took part in Wave 2 representing an overall response rate of This response rate was as the of Wave 2 CAPI interviews that were obtained from the Wave 1 In total, interviews and interviews were Table 3 the response rates and of those who in Wave CAPI response rates at Wave 2 were similar to those of Wave 1. with Wave a of in Wave 2 with of the sample were aged with of the sample in the to and aged years. of participants were or for for were or for for a of the sample living of the sample had at education, with a having a The sample were thus with the NI population. than of the participants in an (i.e. or within a were from and were from Belfast NICOLA Wave 2 CAPI response rates by and NICOLA, Northern Ireland Cohort for the Longitudinal Study of computer-assisted personal self-completion questionnaire. for the self-completion questionnaire not as data is NICOLA Wave 2 CAPI response rates by and NICOLA, Northern Ireland Cohort for the Longitudinal Study of computer-assisted personal self-completion questionnaire. for the self-completion questionnaire not as data is from Wave 2 will provide a analysis and how the of adults in NI have the period between Wave 1 and Wave 2 (i.e. with a particular focus on in economic physical and health, health and social care and of The study aims designed to as as with those of and and its research to the determinants of and economic the impact of cognitive and on the determinants of and and the of social participation on and the of and determinants on health and (see Table 1). The NICOLA study aims to maximize its impact through the use of administrative data All NICOLA participants flagged on the National Health Applications and Infrastructure Services from the General Register Office on and of registered address information is used to when a NICOLA cohort member has NICOLA a linkage within administrative data via the BSO for data of participants. As of the of March were NICOLA participants. with will enable wider anonymized linkages for research, research being for linkage of NICOLA data to routinely collected health and social care data from the BSO and and also linkage with the Northern Ireland Cancer Registry6. Examples of such data include and care data including hospital and the will provide information on in community for NICOLA participants. In March NICOLA also one of many studies to a research the UK Longitudinal Collaboration is within the Longitudinal Health and National Study of the study The UK has been designed to studies such as NICOLA to to the research and policy in response to the It data from longitudinal studies and the linkage and of data to health and administrative records, thus providing and of and enabling to research questions to government policy and of NICOLA in its sample size and the questionnaire and the and of of ageing in Northern Ireland and their and social including the The of NICOLA is also being through its data The impact of NICOLA is through its and on this, and of and with and to the participants to the the of the study A common to many of the ageing cohort is in the of to participants living in private is also an response in terms of of those with The study was designed to be representative of the as with all the of in that the study may have individuals. Although also included within the the number included within this in NI not be to robust NICOLA Wave 1 and Wave 2 data maintained and at a within the Centre for Public Health, Queen’s University and from the practitioner and policy who to the anonymized data set from the first survey can by an application using the Research available on the study including, but not data and data can also be via the NICOLA at data is via the NICOLA within the Centre for Public Health, Queen’s University also archived on an with the UK Data and the UK In the the NICOLA team also to via the Dementias Platform It is also the intention of the study team to with the and harmonization the Gateway to Global Aging Data thus facilitating research by identifying between NICOLA and other ageing cohort The NICOLA study is and ethically and approved via the of and of Queen’s University Belfast written informed consent to participation in the can of the and were for study and and the initial of the and the analysis and of All of the to the of the and of the final Economic and Social Research Northern Ireland Health and Social Care Research and Development Atlantic Centre for Ageing Research and Development Ireland. Office of the and Northern Ireland. The Wellcome Queen’s University to all the participants of the NICOLA study and the NICOLA includes nursing research and and The for the of the data and or those of the and not those of the NICOLA study team.

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