Age related cognitive decline: a clinical entity? A longitudinal study of cerebral blood flow and memory performance.

OBJECTIVES: To evaluate the changes in regional cerebral blood flow (rCBF) and memory performance in patients with age related cognitive decline (ARCD) who did and did not become demented during a follow up period. METHODS: Twenty four patients with ARCD were recruited from an outpatient memory clinic, of whom 18 were followed up over a mean period of two years. Eighteen patients with mild to moderate probable Alzheimer's disease and 18 aged normal controls were followed up over a mean period of three years. Memory performance and rCBF were evaluated quantitatively at inclusion and during follow up, using single photon emission computed tomography with xenon-133 injection and three subtests of the Wechsler memory scale (logical memory, paired associated learning, and digit span). RESULTS: Patients with ARCD showed decreased rCBF and memory performance at initial evaluation compared with controls. Five of them became demented during the follow up period, with further decline in memory and rCBF. At inclusion, the only feature that distinguished these five patients as a group from the remainder was a pronounced temporoparietal asymmetry. The 13 patients with ARCD who did not become demented still exhibited impaired memory and rCBF at follow up, but without any further decline and no increase in flow asymmetry. CONCLUSIONS: Apart from patients in the preclinical phase of Alzheimer's disease, the ARCD category includes non-demented patients who have brain dysfunction that may represent a distinct clinical entity.