The Healthy Cognitive Ageing Project (ELSA-HCAP) aims to investigate dementia risk using the Harmonised Cognitive Assessment Protocol (HCAP), as part of an international research collaboration funded by the National Institute on Aging (NIA).
 

The Harmonised Cognitive Assessment Protocol

 

The protocol has been designed to leverage the Health and Retirement Study (HRS) international network of studies to produce comparable data on cognition and research diagnoses of dementia and mild cognitive impairment, to support joint epidemiological analysis of the aetiology and impact of cognitive decline and to make comparable national estimates of the dementia prevalence around the world.

 

This tool consists of cognitive assessments that harmonise well with prior studies, including the 10/66 studies, the Rush University Memory and Aging Project and the HRS dementia study known as ADAMS. Versions of HCAP will also be conducted in the US, Mexico, India, China, and South Africa.

​

For more information on the HCAP Network, visit: https://hcap.isr.umich.edu/

 

The ELSA-HCAP study

 

HCAP1

​

The first wave of the ELSA-HCAP study was carried out in 2018 through face-to-face interviews in participants’ homes or institution in which they live, by a trained survey interviewer using CAPI methods. HCAP1 involved 1,274 ELSA participants aged 65 and older, of whom 676 participants were sampled with normal cognition, 419 with probable Mild Cognitive Impairment (MCI) and 179 with dementia. A total of 1,137 family/informant interviews (618 normal cognition, 365 probable MCI and 154 with dementia) were completed.

 

A weighting procedure was derived for this wave to adjust for non-response bias within each of the three cognition groups, especially for the low cognition group, which had the lowest response rate. It involved three components: design weights, non-response weights, and a calibration procedure accounting for differential selection probabilities and adjusting for non-response. The final weight for this study represents a combination of the design and non-response weights. For more information on sample weights for the first wave of the ELSA-HCAP study, click here.

 

HCAP2

​

The second wave of the ELSA-HCAP study was conducted from April to October 2023 using a similar methodology to HCAP1 (with some improvements to fieldwork implementation). This wave aimed to investigate cognitive function and characterize longitudinal trajectories in older adults within the ELSA cohort, including those from minoritized ethnic communities and individuals at the end of life.

​

The HCAP2 sample consists of three groups: respondents from HCAP1 (tracking a 5-year trajectory of change), ELSA respondents from ethnic minority communities (targeting 300 participants), and randomly selected ELSA respondents aged 65 and older to enhance statistical power. A total of 2022 respondents were interviewed. Among these, 547 had participated in HCAP1 and 307 were from ethnic minority communities. Additionally, 1814 family/informant interviews were conducted out of the 2022 invited sample. A total of 173 end-of-life interviews with informants of deceased ELSA participants were also completed.

​

A weighting procedure was also derived for this wave to separately adjust for follow up (i.e., a longitudinal weight) for those HCAP2 respondents who also took part at HCAP1, and non-response (i.e., a combination of a design weight and a non-response weight) for HCAP2 respondents who did not take part at HCAP1. These weights were then subjected to a calibration procedure to match population estimates for the purposes of analysing data from all HCAP2 participants.

 

Data access 

​

​Data for HCAP1 and HCAP2 including sample weights are available on the UKDS website.​ Please refer to the technical reports available with the data for more information.

 

Related publications

​

Cadar D, Abell J, Matthews FE, Brayne C, David Batty G, Llewellyn DJ, et al. Cohort Profile Update: The Harmonised Cognitive Assessment Protocol Sub-study of the English Longitudinal Study of Ageing (ELSA-HCAP). Int J Epidemiol. 2021;50(3):725-6i. DOI:10.1093/ije/dyaa227 pmcid:PMC8271185 [Link]

 

Liu Y, Hayat S, Assaad S, Cadar D, Steptoe A, Lee J, Gross AL. Harmonized Cognitive Assessment Protocol in the English Longitudinal Study of Ageing: Contrasting approaches to evaluation of factor structure. International Psychogeriatrics. 2025 Feb 5:100042.

 

Assaad S, Hayat S, Brayne C, Zaninotto P, Steptoe A. Factors associated with non-participation in the healthy cognitive ageing project. Alzheimer’s & Dementia. 2025; (in press); DOI: 10.1002/alz.70169

 

Hayat S, Assaad S, Ahmed N, Brayne C, Steptoe A. A study evaluation framework for measuring cognition using the Harmonized Cognitive Assessment Protocol (HCAP). Lessons learned in cross-national contexts from four English-speaking cohort studies of aging. (under review)