In addition to the human suffering caused by dementia, there is also a significant economic cost to society. The cost of dementia in the UK is estimated around £26 billion, two-thirds (£17 billion) of which is paid by the people with dementia and their families as unpaid care or private social care. Therefore, efforts towards dementia prevention and delaying of its onset are paramount in improving the lives of older people, as well as their families and communities.

With dementia being undetected in almost half of primary care patients in the UK, population-based studies play an integral role in providing the evidence-base for better planning, policy-making, and prevention. In particular, longitudinal studies with repeated interviewing of a cohort or panel over time, provide great insights into risk and protective factors at early, mid, and later life that can lead to the development of dementia.

Understanding cognition through harmonised data.

The Healthy Cognitive Ageing Project (HCAP), is part of the international Harmonized Cognitive Assessment Protocol (also abbreviated as HCAP), which is a platform for understanding cognition through harmonised data – that is data collected using similar questions and methods. The HCAP Network includes sister studies in the USA, Ireland, Mexico, South Africa, China, and India and is expanding to include other cohorts, particularly from low and middle income countries (LMICs).

In the absence of a single measurement instrument for dementia identification and classification, the aim of this platform is to better characterise cognitive function among older people, describing the spectrum of cognitive ageing from normal, to mild impairment, to severe impairment or dementia. This is done using a standardised set of tests which cover key cognitive domains such as learning, memory, language, visual perception, planning, decision-making, and attention.

In 2018, a total of 1,273 participants were interviewed as part of the ELSA-HCAP study. Baseline results showed significant gender/sex differences in cognitive function across several of the tests which warranted further investigation. Currently, the research team is implementing the second wave of data collection (started in April 2023) to enable the detection of changes in cognitive functions after 5 years of follow-up.

Better representation, harmonisation, and evidence-based recommendations

The second wave of ELSA-HCAP study will include a higher representation of the ethnic minority groups in the UK compared to the baseline sample. This is to enable understanding of cognitive ageing within this segment of the population which is less studied and at a greater risk of developing vascular and early onset dementia.

Communications with the HCAP Network, and analysis of data and lessons learned from fieldwork of the baseline ELSA-HCAP study, have enabled the research team to improve the methods and adaptation of the questions within the English setting. This work will facilitate the implementation of future waves of data collection as well as cross-country reproducibility and comparisons.

Adding to the methodological implications of this work, the collection of follow-up data in ELSA-HCAP will enable a better understanding of dementia and changes in cognition in older people living in England as well as lifestyle and behavioural factors that contribute to these changes. The results will inform policy and social interventions to better support people living with dementia and their families.

With dementia becoming an increasingly important topic locally and globally, the research team is excited to study, for the first time, dementia and cognition in detail, tapping into the various cognitive domains, and hopes to contribute to the evidence needed to improve the lives of people living with dementia and their families.