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Make the Diagnosis: Dementia

Prior Probability

Dementia consists of multiple cognitive deficits that include memory impairment and at least 1 of the following cognitive disturbances: agnosia, aphasia, apraxia, or a disturbance in executive functioning (see Box 63-1). Overall, the prevalence of dementia among patients 65 years or older is 6%-16%. This prior probability can be refined by recognizing that age is the most important risk factor for dementia. Dementia exists in only 1% of patients in the sixth decade of life, but the prevalence doubles every 5 years so that by age 90 about 39% of elders are affected.

Box 63-1Defining Dementia and Related Termsa

Patients for Whom Dementia Should Be Considered

Despite the high prevalence of dementia in older adults, the US Preventive Services Task Force suggests that there is not enough evidence to recommend for or against systematic screening.1 With aging, normal adults experience some memory loss. While patients who claim memory loss may have dementia [likelihood ratio (LR) 1.8, (1.5-2.2)], they may also have depression or the complaints may reflect their underlying personalities. Nonetheless, patients should be assessed for dementia if they claim memory loss or when people with knowledge of the patients note that the patients have memory deficits [LR 6.5 (4.4-9.6)] or behavioral changes (see Box 63-1).

Assessing the Likelihood That a Patient Has Dementia

The Mini-Mental Status Examination (MMSE) is the best-studied screening test for dementia. However, the test takes time and because it is copyrighted the examiner must use it from an approved source. The MMSE norm varies with education and age so the appropriate threshold is sometimes adjusted for age and years of education, but ...

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