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The Healthy Cognitive Ageing Project (ELSA-HCAP)

The Healthy Cognitive Ageing Project (HCAP) aims to investigate dementia risk using a harmonised cognitive assessment protocol, as part of an international research collaboration funded by the National Institute on Aging (NIA).


The first wave of HCAP cognitive assessments were carried out in 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.


The HCAP 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.


The protocol was designed to 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:

Data collection for HCAP1 has been completed and the data are now available on the UKDS website.

Data collection for HCAP2 started in April 2023 and was completed in October 2023. Data will be available in early 2024.  

Study profile

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]


Sample weights  


A weighting procedure was derived for the ELSA-HCAP substudy in order 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 sub-study represents a combination of the design and non-response weights, which is made available to the users with the ELSA-HCAP data available on the UKDS website


For more information on sample weights, click here.

Study team

Principal Investigator: Professor Andrew Steptoe


Co-Investigators: Professor Paola Zaninotto (UCL), Professor Carol Brayne (University of Cambridge)


Collaborators: Professor David Weir (University of Michigan), Professor Kenneth Langa (University of Michigan), Professor Ian Deary (University of Edinburgh), Professor Martin Prince (King's College London)


Researchers: Dr Shabina Hayat and Sarah Assaad (University College London)


Contact: Dr Shabina Hayat

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