The outlook of a mild cognitive impairment diagnosis: disease-specific symptoms may forewarn of decline

By 18th June 2020Blog, Research

For each person living with a dementia diagnosis, the journey can be very different, and no two stories are the same. The particular everyday difficulties one encounters can vary enormously, from difficulties with language or making sense of complex concepts and decision making, to forgetfulness, or visual challenges. Sometimes these differences can be traced back to the biological cause responsible for this condition in each person. For example, a dementia which arises due to specific small protein clumps called ‘Lewy bodies’ within brain cells will often cause different symptoms to the more common Alzheimer’s disease. This may include a variety of psychiatric and physical symptoms such as complex visual hallucinations, movement problems, vivid dreams, and considerable moment-to-moment variation in levels of alertness. All of these symptoms come with their own particular management needs. People with Lewy body dementias often have a worse outlook with greater risk of hospitalisation, admission to full-time care, and shorter survival time. This makes it vitally important to recognise what type of dementia someone has early in the condition.

There is increasing interest in finding ways to diagnose dementia earlier. Researchers and clinicians hope to identify people at risk before they develop this condition, as this may be the best time to intervene and prepare to manage the condition. This is where the concept of ‘mild cognitive impairment’, or MCI, may help to bridge the gap. Dementia does not typically arise overnight. Most people who develop dementia likely experience mild symptoms that subtly escalate for many years; an assessment that may ring true for many people with dementia and their family members. Recent research has suggested that as many as one in three cases of dementia may be preventable through early changes to lifestyle and health, showing the potential benefits of early and accurate diagnosis.

It is becoming clear that recognising what type of dementia a person will develop, such as Alzheimer’s or Lewy body dementia, may be possible when people are experiencing only mild symptoms, but it is less clear if these conditions differ in their prognosis at these early stages. As with dementia, the condition of mild cognitive impairment may vary enormously between individuals. Whilst some worsen over time towards dementia, many remain stable or even appear to recover to their previous function. One drawback of earlier diagnosis may be a loss of accuracy in identifying degenerative diseases. It is currently difficult to predict which individuals’ conditions will, or will not, worsen, how fast this might happen, and why this might differ between people. Answering any or all of these questions may provide valuable information to people receiving a diagnosis, and their families.

At Newcastle University, we assessed seventy-six people annually after they receive a diagnosis of mild cognitive impairment. This allows us to track their change in function over time, such as in their memory and thinking abilities, or their ability to carry out daily tasks. With thorough assessment, our clinical panel are able to establish which cases of mild cognitive impairment appear to have symptoms reflecting Lewy body disease, and which appear to be due to Alzheimer’s disease instead (for this study, all other causes were excluded). By testing their functioning each year, we are  able to characterise people into discrete groups based on how their cognitive problems progress, such as problems with memory, attention and vision, and difficulties understanding or using speech and complex reasoning. We identified groups of people whose symptoms remain relatively stable over time, or who appear to get progressively worse. While the majority of people appear to develop greater cognitive problems, as many as 40% do not measurably decline over a two-to-five year period. Crucially, this is not the same across the two diagnostic groups; participants who experience symptoms or have brain imaging findings associated with Lewy bodies, are more likely to demonstrate increasing cognitive problems, while the Alzheimer’s disease group appear more stable in the short-term. Additionally, we found that people experiencing one particular hallmark symptom of Lewy body disease, complex visual hallucinations, are more likely to deteriorate in function.

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When tracked over time, people with a mild cognitive impairment develop in a variety of ways: some remain stable (blue), others progressively worsen (green), while some worsen very quickly (red).

The findings of this study are consistent with the current understanding that Lewy body disease has a slightly worse prognosis in dementia than Alzheimer’s disease. It expands on this by suggesting that these differences in prognosis may already be present before significant dementia onset, and that people with mild symptoms associated with Lewy body disease are  more likely to develop dementia within two-to-five years than people with mild symptoms of Alzheimer’s disease.  Not all symptoms associated with Lewy bodies come with equal risk: those experiencing visual hallucinations are particularly likely to continue to decline. There may be value in identifying the presence or absence of specific symptoms such as visual hallucinations during these early mild stages, as they may highlight which individuals are most likely to decline or remain stable over the following years.

While these findings are focused on a particular diagnostic niche – the early comparison of Alzheimer’s and Lewy body diseases – the hope is that information such as this will become increasingly relevant as dementia research continues a shift towards diagnosis at the early symptom stages, helping to differentiate people at risk of progressive decline from those likely to remain stable or recover. Earlier diagnosis and better understanding of prognosis will allow researchers and clinicians to develop earlier support services for people with different types of dementia, and trial drug treatments in people before they demonstrate significant cognitive problems. It will also allow us to provide detailed and accurate information to people with dementia and their families on what they may experience throughout the course of the condition. While we continue to search for a cure for all types of dementia, it is critical that we diagnose people early and accurately to ensure we can provide them with the best quality information, care and treatment possible.

Calum Hamilton is a third-year PhD student at the Newcastle University Translational and Clinical Research Institute, Newcastle upon Tyne, UK, exploring how a mild cognitive impairment may differ between Lewy body and Alzheimer’s disease, and how these develop over time.

Email: C.Hamilton3@Newcastle.ac.uk.

Twitter: @CalumAHamilton

This blog describes findings from the ‘LewyPro’ study, funded by research grants from the NIHR Newcastle Biomedical Research Centre and Alzheimer’s Research UK. These results have been published in full in Psychological Medicine.

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