First ever population-based research in Alzheimer's disease finds key causal factor to be more prevalent in the over 85's and less prevalent in the 70-74 group than previously thought
New research, published in Nature, has provided the first ever population-based data on the frequency of Alzheimer's disease neuropathological changes (ADNC) - a key causal factor behind the development of dementia - and found that it is more prevalent than previously thought in the oldest age groups (eg 85+) but lower in those under 75. These changes were less common in people with higher education levels.
The research, conducted by King's College London, Stavanger University Hospital, and University of Gothenburg, used a simple non-invasive blood test to establish that more than 1 in 10 adults over 70 met the eligibility criteria for monoclonal antibody treatments that are capable of slowing cognitive decline.
ADNC are deposits of proteins in the brain that result in the death of neurons and synapses, particularly in the hippocampus, which is vital for memory. While they are an excellent biomarker and early sign for the potential development of Alzheimer's and other related diseases, testing for it in England on the NHS requires either a lumbar puncture to analyse cerebrospinal fluids, or a PET scan. As such, the true prevalence of ADNC has been difficult to establish.
In this study, researchers worked with members of the The Trøndelag Health Study (HUNT) in Norway to analyse 11 486 blood samples provided by participants over the age of 57 in the local population.
Their anaylsis of the data found that the prevalence of ADNC increased with age; just under eight per cent of participants aged 65 to 69 compared to 65 per cent of the over 90s had clearly abnormal findings on the biomarker. Researchers suggest this shows evidence of a higher prevalence of Alzheimer's dementia in older individuals and a lower prevalence of preclinical Alzheimer's disease in younger groups than previously estimated.
In an aging global population, the assessment and treatment of dementia presents a significant challenge. Our study used a simple blood test to establish changes that contribute to cognitive impairment in those with dementia.
Professor Dag Aarsland, a Professor of Old Age Psychiatry at King's IoPPN and the study's lead author
Further analysis however revealed that among those participants over the age of 70, ADNC was present in 60 per cent of people with dementia, and in 32.6 per cent of those with mild cognitive impairment. These findings show that factors other than ADNC are important contributors to dementia.
The findings challenge previously held beliefs about the nature of dementia, including that it is a "female dominant" disease. Researchers were unable to find any significant differences in prevalence between the sexes at any age group.
Professor Dag Aarsland, a Professor of Old Age Psychiatry at King's IoPPN and the study's lead author said,"We found that around 11 per cent of participants over the age of 70 meet the eligibility criteria for monoclonal antibody treatments that can potentially slow the impact of cognitive decline in these individuals.
"If we are to meet this global challenge, it is vital that we are able to detect signs of dementia at the earliest possible stages. This blood test looks to be an effective means of providing that clarity at scale."
The blood test used in this study is not available on the NHS.
The researchers are now exploring how well these blood-based biomarkers can predict the development of dementia. They also want to work with GPs to find out how these tests can be used in primary care.
Prevalence of Alzheimer's Disease Pathology in the Community - The HUNT Study (DOI ) (Aarsland, Ashton et al) was published in Nature.
