Neuropsychological tests accurately predict incident Alzheimer disease after 5 and 10 years

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Abstract
Objective: To determine whether neuropsychological tests accurately predict incident Alzheimer disease (AD) after 5 and 10 years in participants of the Canadian Study of Health and Aging (CSHA) who were initially nondemented. Methods: The CSHA was conducted in three waves: CSHA-1 (1991 to 1992), CSHA-2 (1996 to 1997), and CSHA-3 (2001 to 2002). The 10-year prediction study included those who completed neuropsychological testing at CSHA-1 and received a diagnostic assessment at CSHA-3 (n = 263). The 5-year prediction study included those who completed neuropsychological testing at CSHA-2 and received a diagnostic assessment at CSHA-3 (n = 551). The diagnostic workup for dementia at CSHA-3 was formulated without knowledge of neuropsychological test performance at CSHA-1 or CSHA-2. The authors excluded cases with a baseline diagnosis of dementia or a prior history of any condition likely to affect the brain. Age and education were included in all analyses as covariates. Results: In the 10-year follow-up study, only one test (short delayed verbal recall) emerged from the forward regression analyses. The model with this test and two covariates was significant, χ2 (3) = 31.61, p < 0.0001 (sensitivity = 73%, specificity = 70%). In the 5-year follow-up study, three tests (short delayed verbal recall, animal fluency, and information) emerged from the forward logistic regression analyses. The model was significant, χ2 (5) = 91.34, p < 0.0001 (sensitivity = 74%, specificity = 83%). Both models were supported with bootstrapping estimates. Conclusions: In a large epidemiologic sample of nondemented participants, neuropsychological tests accurately predicted conversion to Alzheimer disease after 5 and 10 years.