WHO SHOULD READ THIS?
All primary care PAs should be able to recognize and treat mild cognitive impairment (MCI) and dementia.
WHAT IS DEMENTIA, AND HOW DOES IT DIFFER FROM MCI?
The diagnosis of dementia as described in the Diagnostic and Statistical Manual of Mental Disorders (4th edition, text revision) requires that the patient have memory impairment plus aphasia, apraxia, agnosia, and/or a disturbance in executive functioning. These deficits must produce significant impairment in occupational or social functioning, represent a decline from a previously higher level of functioning, and be separate from other psychiatric or neurologic disorders.1
Dementia typically manifests after age 50 years, becomes more common with advancing age, and is more prevalent in men than women after 80 years.2 Approximately 5.3 million persons in the United States have Alzheimer's dementia (AD), and this population is growing.3 In persons 65 years and older, AD accounts for half of all forms of dementia, but only one-third of demented younger persons have AD.2 The greatest risk factor for dementia is being 65 years or older. Other risk factors include lower level of education, family history of dementia, genetic mutations, and vascular disease.2 While dementia affects 1% to 2% of the general population,4 the progression from MCI to dementia may be 12% or more per year,4,5 suggesting that persons with MCI have an accelerated risk for dementia.
MCI represents a vague prodromal stage between normal cognitive function and dementia and it is often confused with normal age-related cognitive changes. Persons with MCI usually present with memory impairment that exceeds the changes seen with normal aging, although other cognitive domains may also be affected. These patients or their family members may describe changes from previous personal norms. MCI has been reported to have a population prevalence of 22% in persons 75 years or older.6 In 80% of patients, MCI progresses to dementia within 6 years of diagnosis.5 Only 5% of patients with MCI have a potential to improve to normal.5
HOW ARE MCI AND DEMENTIA DIAGNOSED?
The diagnostic criteria for MCI are described in Figure 1.4 MCI is subclassified into amnestic (memory-impairment) and nonamnestic (nonmemory-impairment) types, each of which is further subclassified based on the clinical presentation and cognitive domains involved.4 The purpose of MCI classification is related to the predictive nature of certain subclassifications. For example, amnestic MCI-single domain is associated with AD, whereas nonamnestic MCI-single domain tends to be associated with frontotemporal dementia.4
Numerous neuropsychological assessment tools are available to assist in the diagnosis of both dementia and MCI. The Mini-Mental State Examination is commonly used by PAs to screen for cognitive changes (MMSE, www.minimental.com). While reliable for dementia, however, the MMSE may be inadequate for MCI screening.7,8 For assessing MCI, the Montreal Cognitive Assessment (MoCA)9 is a validated test which is available free at www.mocatest. org (see Table 1 for other useful Web sites). The MoCA was reported to have 90% sensitivity and specificity for identifying MCI, compared with only 18% for the MMSE.9 The MoCA distinguishes between normal age-related cognitive changes and MCI and requires approximately 10 minutes to administer, but it does not distinguish between MCI and dementia with certainty. PAs should become familiar with this screening tool and consider it for evaluating questionable cognitive changes in adult patients.