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  • Impairment in at least two of the following cognitive domains: memory, executive function, language, visuospatial function, and personality/behavior.

  • Significant impairment in social or occupational functioning.

  • Significant decline from previous level of function.

  • Deficits not occurring solely in the presence of delirium or accounted for by major psychiatric disorder.


The prevalence of dementia approximately doubles every 5 years after 60 years. Among community-dwelling elders older than 85 years, the prevalence is estimated to be 25% to 45%. Prevalence is even higher in nursing homes (>50%). Approximately 60% to 70% of dementia cases are attributable to Alzheimer disease (AD), either alone or mixed with Lewy body dementia (DLB) or vascular dementia (VaD), the next two most common forms of dementia in older adults. Frontotemporal dementia (FTD) is typically thought of as a common cause of early-onset dementia (age of onset <65 years old) and is less common in older adults, although likely underdiagnosed.

Cognitive function in older adults is considered a spectrum and ranges from cognitive changes seen in normal aging to mild cognitive impairment (MCI) to dementia. Compared with younger adults, older adults often perform more slowly on timed tasks and have slower reaction times. Mild memory changes may be present with subjective problems such as difficulty recalling names or where an object was placed. In the case of normal aging, however, the person usually remembers the information later and has intact learning, and any deficits in memory function are subtle, relatively stable over time, and do not cause functional impairment.

MCI is a disorder in which cognitive function is below normal limits for that patient’s age and education but is not severe enough to qualify as dementia. MCI is characterized by subjective cognitive complaints, preferably corroborated by someone else; evidence of objective cognitive impairment in one or more cognitive domains (eg, memory, language, executive function); and intact functional status. When MCI involves memory (amnestic MCI), it is associated with an increased risk of AD and often represents a very early AD process. Among patients with amnestic MCI, 10% to 15% per year convert to AD compared with 1% to 2% of age-matched controls. Although many patients with MCI will progress to AD with time, it is a clinically heterogeneous group, with some patients progressing to other types of dementias and others remaining cognitively stable. The most severe type of cognitive impairment is dementia. This diagnosis requires deficits in multiple domains of cognitive functioning (at least two) that represent a significant change from baseline and that are severe enough to cause impairment in daily functioning (see “Essentials of Diagnosis,” earlier).

Dementia often goes undiagnosed or undocumented in primary care settings, especially early in the course of the disease. Cognitive impairment and dementia should be detected as early as possible in older patients so that secondary causes of cognitive ...

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