Multiple cognitive deficits in patients during the mild cognitive impairment stage of Alzheimer's disease: how are cognitive domains other than episodic memory impaired?

Background: Little is known about how cognitive domains other than episodic memory are affected during the mild cognitive impairment (MCI) stage of Alzheimer's disease (AD). We attempted to clarify this issue in this study. Methods: Fifty-seven Japanese subjects were divided into two groups: one comprising people in the MCI stage of AD (MCI group, n = 28) and the other of normal controls (NC group, n = 29). Cognitive functions were assessed using the Japanese version of the neurobehavioral cognitive status examination (J-COGNISTAT). Results: The MCI group performed significantly worse than the NC group on subtests that assessed orientation, confrontational naming, constructive ability, episodic memory, and abstract thinking. Three-quarters of the MCI group had deficits in memory and other non-mnemonic domains, particularly constructive ability and abstract thinking. However, within-subject comparisons showed that the MCI group performed significantly worse on the memory subtest compared to any other subtest. Conclusions: Besides episodic memory, multiple non-mnemonic cognitive domains, such as constructive ability and abstract thinking, are also impaired during the MCI stage of AD; however, these non-mnemonic deficits are smaller than episodic memory impairment.