Diagnosing mild cognitive impairment (MCI) is more important than ever, experts say
Increasing recognition of MCI as an early stage on the continuum of Alzheimer’s disease (AD) in some patients has led experts to call for improved diagnosis of MCI, while research examines ways to halt or slow the disease process following early diagnosis.
In ‘MCI on the Alzheimer’s continuum’, one of a series of Mind Changers podcasts hosted on the recently launched ADBioHub, Prof Philip Morris (Medical Director of the Gold Coast Memories Disorder Clinic) and A/Prof Michael Woodward (Head of Aged and Residential Care Services at Austin Health in Melbourne) discussed how our understanding of MCI is changing as clinical research pushes the threshold for diagnosis earlier in the disease continuum.
Defining MCI
MCI is defined as declines in performance of one or more cognitive domains with the preservation of functional independence.1 MCI may be amnestic (i.e. affecting memory) or non-amnestic (i.e. not affecting memory).2 While the person or their family members will have noticed a change in cognition, it is not so severe that it affects their independence in everyday activities.2
If the person progresses to cognitive decline that results in difficulties managing their everyday life, this is then classified as dementia.2 The differential diagnosis between normal ageing and MCI, as between MCI and mild dementia, is challenging because the boundaries are inherently arbitrary along the disease continuum.2
Significance of amnestic MCI
Amnestic and non-amnestic forms of MCI have a number of different underlying causes with a range of variable outcomes.3 In a subset of patients with amnestic MCI, this represents the prodromal stage of dementia due to AD.3
As explained by A/Prof Michael Woodward in ‘MCI on the Alzheimer’s continuum‘, “We know from studies such as AIBL [the Australian Imaging, Biomarker & Lifestyle Flagship Study of Ageing]… that over the next 3–5 years, at least 50% of people with MCI will develop dementia, usually due to AD.” 4
The role of biomarkers in the early diagnosis of AD
According to A/Prof Woodward, “We understood that AD gets more severe as time goes on from the very beginning, but this idea of earlier stages – preclinical and prodromal stages of AD – has only been defined over the last 20 to 25 years, in particular, as a result of studies such as AIBL [the Australian Imaging, Biomarker & Lifestyle Flagship Study of Ageing] and ADNI [the Alzheimer’s Disease Neuroimaging Initiative]… Through the use of biomarkers and other tests we are now getting a much more comprehensive picture of what happens in AD.”
Indeed, research on biomarkers has allowed the AD continuum to be divided into three overlapping areas:5