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Roy C. Martin, PhD; Shannon M. Annis, MS; Laurie Z. Darling, BA; Virginia Wadley, PhD; Lindy Harrell, MD, PhD; Daniel C. Marson, JD, PhD

Arch Neurol. 2003;60:1585-1589.

Background  Calculation deficits are a common early manifestation of Alzheimer disease (AD).

Objective  To investigate oral and written calculation skills in AD patients using quantitative and qualitative methods.

Design  Comparison among controls, patients with mild AD, and patients with moderate AD on measures of arithmetic skill.

Setting  Tertiary care university medical center.

Participants  Twenty patients with AD (11 with mild AD, 9 with moderate AD) and 23 elderly controls.

Main Outcome Measures  Tests of oral arithmetic (Wechsler Adult Intelligence Scale–Third Edition [WAIS-III] Arithmetic subtest) and written arithmetic (Wide Range Achievement Test-3 [WRAT-3] Arithmetic subtest) were administered, and overall group differences were examined. Errors on selected WRAT-3 problems were qualitatively analyzed across groups using a set of error codes.

Results  Patients with mild and moderate AD performed significantly below controls on both oral and written arithmetic tasks (P<.001). Patients with moderate AD performed worse than those with mild AD on written arithmetic (P<.002) but not on oral arithmetic tasks. On selected WRAT-3 problems, single- and multiple-digit addition and subtraction operations and single-digit division operations were preserved in patients with mild AD. In contrast, only single-digit addition was preserved in patients with moderate AD. Errors of operation substitution and number position were the most common error types observed in AD patients. Patients with moderate AD displayed multiple error types and high incidence rates compared with controls, while patients with mild AD exhibited error types and incidence rates intermediate to controls and patients with moderate AD.

Conclusions  A decline in calculation abilities is one of the hallmark cognitive features of AD. Patients with mild AD maintain relative preservation of simple written calculation skills but demonstrate marked impairment as task complexity increases. Patients with moderate AD demonstrate global impairments extending to the simplest arithmetic skills. These findings suggest that loss of calculation abilities in AD is both hierarchical (by arithmetic operation) and a function of disease severity.

From the Department of Neurology (Drs Martin, Harrell, and Marson and Mss Annis and Darling), Alzheimer's Disease Research Center (Drs Harrell and Marson), Center for Aging (Dr Marson), and the Department of Psychology (Drs Wadley and Marson and Mss Annis and Darling), University of Alabama–Birmingham.

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