Definition and Overview
A cognitive function test is a neuropsychological assessment that objectively measures the state of cognitive function using standardized tools. Several cognitive areas, including memory, language, visuospatial ability, executive function, and attention, are evaluated to identify the presence and extent of cognitive decline and the affected areas.
Tests are broadly divided into two types. It is a screening test that measures overall cognitive status in a short period of time, and a precise neuropsychological test that subdivides and evaluates cognitive areas in detail. In clinical practice, a stepwise approach is used in which cognitive decline is suspected through a screening test, followed by a detailed test.
screening test
Mini-Mental State Examination (MMSE)
The Mini-Mental State Examination (MMSE) is a representative screening test with a score out of 30. It evaluates orientation, memory registration and recall, attention and calculation, language, and visuospatial organization, and is administered in approximately 10 minutes. The lower the score, the higher the possibility of cognitive decline, but the cut point is interpreted by adjusting for education level and age.
Montreal Cognitive Assessment (MoCA)
The Montreal Cognitive Assessment (MoCA) is also scored out of 30 and evaluates executive function, attention, delayed recall, etc. in more detail. It has high sensitivity in screening for mild cognitive impairment and is useful in detecting early changes that result in normal results on the MMSE. In a meta-analysis comparing cognitive testing tools, it was reported that the diagnostic accuracy of screening tests varies depending on the tool and cut point.
Precise neuropsychological test
A detailed neuropsychological test subdivides cognitive areas and evaluates them over 1 to 2 hours.
- Memory: immediate recall, delayed recall, and recognition of verbal and visual information
- Language: naming, fluency, repeating, comprehension
- visuospatial: copying shapes, drawing clocks, spatial construction skills
- Executive functions: planning, abstraction, inhibition, cognitive switching.
- Attention: Sustained attention, working memory, speed of information processing.
Through domain-specific evaluation, it is possible to determine which cognitive domain was damaged first and to what extent, contributing to distinguishing the pattern of the causative disease. For example, in Alzheimer's disease, memory areas tend to be affected first, and in frontotemporal dementia, executive function and language tend to be affected first.
Severity Assessment
The Clinical Dementia Rating (CDR) evaluates changes in daily functioning in six areas: memory, orientation, judgment/problem solving, social activities, family life, and hygiene, and indicates severity as 0 (normal), 0.5 (borderline), 1 (mild), 2 (moderate), and 3 (severe). It is used to estimate the stage of dementia and track its progress based on functional changes rather than scores.
Uses and Limitations
Cognitive function testing is a key tool for objectively confirming cognitive decline, assessing its severity, and tracking its progress. However, dementia cannot be confirmed based on test results alone. Education level, age, depression, anxiety, and physical condition at the time of testing affect the results, and even the same score may have different clinical meaning.
Therefore, test results are interpreted in combination with medical history, neurological examination, brain imaging, blood tests, and, if necessary, biomarker tests. Follow-up tests at regular intervals are more useful in identifying patterns of change than tests at one point in time.