Identification of early cognitive change in diverse African populations. A harmonisation consortium to inform future dementia prevention studies.

This study will benefit older people living in Africa who are at risk of getting dementia, specifically Alzheimer's disease, the most common type of dementia worldwide.

Over two thirds of people with dementia worldwide live in countries classified as 'low and middle income'. These 'low and middle income' countries have lower resources per person to cope with the challenges of dementia. This includes most African countries, where numbers of people with dementia are growing rapidly, because people are living longer due to better healthcare. We know that up to four in ten dementias could be prevented. Despite this, almost all research on how to prevent dementia has been done in and for, 'high income' countries like the UK.

The earliest changes of Alzheimer's disease happen years prior to diagnosis. By the time there is obvious memory difficulty, the underlying brain damage is widespread and may be irreversible. Researchers have started to create ways of measuring these earliest changes through tests of brain functions which may be affected earlier than memory. These include tests of language, and one's ability to find one's way (navigation).

Currently, we do not have tests to identify these early Alzheimer's disease changes in older people in Africa. It is well-known that culture and education affect performance on cognitive tests, and that measures designed in high income countries are unlikely to work well. We need African tests of the brain functions we know to be affected in early Alzheimer's disease, that are comparable to high-income country tests so that joint studies can be conducted. This study will create a formal partnership of community groups, people with dementia, Ministry of Health representatives, and academic researchers with experience of designing tests for early Alzheimer's disease in other countries to address these issues.

In Tanzania, we will collaborate with local communities and dementia groups to evaluate existing tests of the brain functions affected earliest in Alzheimer's disease, adapt these tests to be acceptable to them and agree on how best to explain tests to older people so that they feel comfortable trying them. We will conduct a series of validation studies in hospital clinics and in a rural community, comparing performance on our adapted early tests to existing dementia tests used in Africa and with clinical diagnosis of Alzheimer's disease by a specialist doctor. Working with volunteers, communities, and the Tanzanian Ministry of Health, we will investigate what the normal test scores should be for an older person in Tanzania. We will ask over 700 people aged 60 and over to volunteer at Government health promotion events, and produce data on test performance by age, educational level, sex, and geographical location. We will work with another population study in Kilimanjaro, to use census data to help us establish a community baseline study and pilot follow-up to find out if our tests are likely to be feasible and useful in studies of change over time. Once we have properly evaluated the tests in Tanzania, the African Dementia Consortium network will repeat our work on normal test scores in their individual countries by training early career researchers. This additional work is planned for Benin, Ethiopia, Kenya, Uganda, Nigeria, Ghana, and Mozambique.

This work will help our partnership of researchers to develop a future African dementia prevention study. This work may later also benefit researchers who work with minority populations in the UK. Our goal is to publish a set of effective tests, which other researchers can easily use. We want African older people to be able to take part in global dementia prevention studies wherever they live so that they have sound information on how to reduce their risk. Having firm evidence that African early Alzheimer's disease tests exist and are useful is the first step in making this happen.

Dementia, the most common cause of which is Alzheimer's disease (AD), is a global health challenge, greatly impacting people living with dementia, families, health systems and economies. Sub-Saharan Africa (SSA) is disproportionately affected. SSA community dementia prevalence is similar to that reported in high-income countries (HICs) but appears to be rising faster, due to population ageing and lifestyle factors.

Up to 40% of dementias are potentially preventable, but prevention research requires early-stage detection. Appropriate early AD measures are not currently available in SSA, limiting participation in global dementia prevention trials.

This CARP award advances understanding of how best to measure early AD changes in older people in Tanzania in a manner both culturally valid and directly comparable to HIC data, enabling future collaboration.

I will focus on cognitive functions with neuropathological and neuropsychological evidence for impairment in early AD, particularly in the two years prior to dementia onset. These include semantic memory, language, spatial navigation and visuoconstruction. I will work with communities, stakeholders and people with dementia in Tanzania to review specialist measures and consider if and how these could be culturally adapted, whilst still measuring the required constructs. Adapted measures will be robustly psychometrically evaluated including diagnostic accuracy data (for AD, ICD-11 dementia, mild cognitive impairment (MCI)) in clinical and community settings, and demographically-stratified normative values.

We will assess feasibility of evaluated early AD measures for use in longitudinal studies through establishment of a community cohort and conducting pilot follow-up. To ensure scale-up and build capacity, the African Dementia Consortium (AfDC) will mentor junior researchers to obtain demographically stratified normative values for selected measures in 7 other countries.