Cognitive test scores in community-based older adults with and without dementia

In an epidemiological survey of a rural, largely blue-collar, community, 1,363 randomly selected adults, aged 65 + years, were administered a cognitive screening battery (including in part the CERAD neuropsychological tests): Mini-Mental State Examination; Word List Learning, Recall, and Recognition; Story, Immediate and Delayed Recall; Boston Naming Test; Verbal Fluency; Temporal Orientation; Constructional Praxis; Draw a Clock; and Trailmaking. Cognitively impaired subjects and cognitively intact controls underwent independent standardized diagnostic assessments and were rated on Clinical Dementia Rating (CDR) scale. Overall, subjects at higher CDR levels (more severe dementia) had worse scores on all tests; showing that standard neuropsychological tests are valid for characterizing the cognitive impairments seen in dementia, even in community settings. However, non-demented scores on the CERAD tests in this community-based sample were lower than reported from CERAD's pooled healthy controls from Alzheimer's Disease Centers (ADCs) nationwide. Thus, 'normal' scores from specialty dementia clinics, where there may be a selection bias, may differ from normative scores from rural and/or less-educated populations. Patients from such populations may be functionally intact despite low test scores. Community-based studies are required to complement specialty clinic-based studies of dementia and cognitive functioning.