offering hope for interventions to reduce the risk of the disease developing.
To date it has been unclear whether it might be possible to detect changes in brain function before the onset of symptoms, so researchers at the University of Cambridge and Cambridge University Hospitals NHS Foundation Trust set out to determine whether people who developed a range of neurodegenerative diagnoses demonstrated reduced cognitive function at their baseline assessment.
The authors explained: “The pathophysiological processes of neurodegenerative diseases begin years before diagnosis. However, prediagnostic changes in cognition and physical function are poorly understood, especially in sporadic neurodegenerative disease.”
Prediagnostic cognitive and functional impairment identified
The researchers analyzed data from the UK Biobank and compared cognitive and functional measures, including problem solving, memory, reaction times and grip strength, as well as data on weight loss and gain and on the number of falls, in individuals who subsequently developed a number of dementia-related diseases (Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, progressive supranuclear palsy, dementia with Lewy bodies, and multiple system atrophy), with those who did not have a neurodegenerative diagnosis. After adjustment for the effects of age, the same measures were regressed against time to diagnosis. The study was published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
The researchers found evidence of prediagnostic cognitive impairment and decline with time, particularly in Alzheimer’s disease where those who went on to develop the disease scored more poorly compared with healthy individuals when it came to problem solving tasks, reaction times, remembering lists of numbers, prospective memory, and pair matching. This was also the case for people who developed frontotemporal dementia, the authors said.
Nol Swaddiwudhipong, MB, of the University of Cambridge, and first author, said: “When we looked back at patients’ histories, it became clear that they were showing some cognitive impairment several years before their symptoms became obvious enough to prompt a diagnosis. The impairments were often subtle, but across a number of aspects of cognition.”
Prediagnostic functional impairment and decline was also observed in multiple diseases, the authors said. People who went on to develop Alzheimer’s disease were more likely than were healthy adults to have had a fall in the previous 12 months, with those patients who went on to develop progressive supranuclear palsy (PSP) being more than twice as likely as healthy individuals to have had a fall.
The time between baseline assessment and diagnosis varied between 4.7 years for dementia with Lewy bodies and 8.3 years for Alzheimer’s disease.
“For every condition studied – including Parkinson’s disease and dementia with Lewy bodies – patients reported poorer overall health at baseline,” said the authors.
Potential for new treatments
The study findings that cognitive and functional decline occurs “years before symptoms become obvious” in multiple neurodegenerative diseases, raises the possibility that in the future at-risk patients could be screened to help select those who would benefit from interventions to reduce their risk of developing one of the conditions, or to help identify patients suitable for recruitment to clinical trials for new treatments.
Dr Swaddiwudhipong emphasized: “This is a step towards us being able to screen people who are at greatest risk – for example, people over 50 or those who have high blood pressure or do not do enough exercise – and intervene at an earlier stage to help them reduce their risk.”
There are currently very few effective treatments for dementia or other forms of neurodegeneration, the authors pointed out, in part because these conditions are often only diagnosed once symptoms appear, whereas the underlying neurodegeneration may have “begun years, even decades, earlier.” This means that by the time patients take part in clinical trials, it may already be too late in the disease process to alter its course, they explained.
Timothy Rittman, BMBS, PhD, department of clinical neurosciences, University of Cambridge, and senior author, explained that the findings could also help identify people who can participate in clinical trials for potential new treatments. “The problem with clinical trials is that by necessity they often recruit patients with a diagnosis, but we know that by this point they are already some way down the road and their condition cannot be stopped. If we can find these individuals early enough, we’ll have a better chance of seeing if the drugs are effective,” he emphasized.
Commenting on the new research, Richard Oakley, PhD, associate director of research at Alzheimer’s Society, said: “Studies like this show the importance in continued investment in dementia research to revolutionize diagnosis and drive new treatments, so one day we will beat dementia.”
The research was funded by the Medical Research Council with support from the NIHR Cambridge Biomedical Research Centre. The authors reported no conflicts of interest.
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