Definition and Overview
Mild cognitive impairment is a clinical condition in which cognitive function is objectively reduced compared to age and education level, but the degree does not reach dementia and independence in daily life is generally maintained. It corresponds to the borderline between normal aging and dementia, and is attracting attention as a pre-stage of dementia.
The key to diagnosis is the cognitive decline complained of by the person or guardian, objective decline confirmed by neuropsychological testing, preserved daily life functions, and confirmation that the person does not meet the criteria for dementia. In ICD-10, it is classified as G31.84.
Classification
Mild cognitive impairment is divided into two types depending on the cognitive domain in which it is deteriorated.
- Amnestic Mild Cognitive Impairment (MCI): The main form is memory decline, and the likelihood of progressing to Alzheimer's disease is relatively high.
- Non-amnestic mild cognitive impairment (MCI): The main form is a decline in areas other than memory, such as attention, language, visuospatial ability, and executive function.
Depending on whether there is one or multiple deteriorated areas, it is further divided into single-area type and multi-area type, and this classification serves as a reference for predicting the cause of the disease in the future.
cause
Mild cognitive impairment is not a single cause but can appear as an early stage of several diseases. The most common underlying cause is Alzheimer's disease pathology, and other degenerative diseases such as cerebrovascular disease, Lewy body pathology, and frontotemporal degeneration are involved.
It is important to differentiate causes that can be improved with correction, such as hypothyroidism, vitamin B12 deficiency, depression, sleep disorders, and drug side effects, because they cause cognitive decline. Vascular risk factors such as high blood pressure, diabetes, and dyslipidemia act as factors that increase the risk of cognitive decline and progression.
symptoms
The key point is that objective cognitive decline is confirmed while independence in daily life is maintained. The following changes often occur:
- Often forgetting recent events and repeating the same questions or stories.
- I often forget my appointments or where I left things.
- I have trouble remembering familiar words or people's names.
- I feel more difficult than before with complex plans or calculations.
However, basic daily activities such as eating, hygiene, money management, and going out can be performed without much help, making it distinct from dementia, which causes significant disruption in daily functions.
diagnosis
Diagnosis aims to objectively confirm cognitive decline and identify its cause.
- History taking: Check the onset time, progression pattern, accompanying symptoms, and level of daily living with the guardian.
- Neuropsychological test (cognitive function test): Confirms objective decline by evaluating memory, language, visuospatial, and executive functions based on age and education level corrections.
- Brain MRI: Check for structural causes such as atrophy, vascular lesions, and normal pressure hydrocephalus.
- Blood tests: rule out correctable causes such as thyroid function, vitamin B12, and electrolytes.
- Biomarkers: When necessary, assess Alzheimer's pathology using amyloid PET or cerebrospinal fluid tests.
In normal aging, test scores are within the standard range, and in dementia, even daily life functions are impaired, while mild cognitive impairment falls in the middle. Demarcating this boundary is the key to diagnosis.
Progress and Management
Approximately 10 to 15% of patients with mild cognitive impairment progress to dementia each year, showing a higher risk of progression than the 1 to 2% per year for the general elderly. The risk of progression is higher when the mnemonic and multidomain type is present and when Alzheimer's pathology is confirmed by biomarkers.
There is currently no definitive treatment to halt progression, and management focuses on controlling risk factors and regular follow-up. Management of vascular risk factors such as high blood pressure, diabetes, and dyslipidemia, regular aerobic exercise, smoking cessation and drinking, cognitive stimulation activities, and treatment of depression and sleep disorders are reported to be helpful in delaying the progression. If dementia progression is confirmed early through follow-up tests every 6 to 12 months, a treatment plan can be developed at an appropriate time.