Neuropsychological Profiles of Elderly Chinese People with Amnestic and Multiple-Domain Mild Cognitive Impairment

Abstract Objective: To compare profiles of neuropsychological impairment in elderly Chinese patients with amnestic, multiple-domain mild cognitive impairment and patients with normal ageing and mild Alzheimer's disease. Patients and Methods: Patients with mild cognitive impairment were categorised into 2 groups: single-domain amnestic mild cognitive impairment (n = 54) and multiple-domain amnestic mild cognitive impairment (n = 93). The scores of neuropsychological tests of patients with mild cognitive impairment were compared with those of cognitively normal elderly controls (n = 78) and patients with mild Alzheimer's disease (n = 85). Results: The 2 groups of patients with mild cognitive impairment had performances in the neuropsychological tests intermediate between the normal controls and patients with mild Alzheimer's disease. Patients in the multiple-domain amnestic mild cognitive impairment group had different profiles of cognitive impairment from those in the single-domain amnestic mild cognitive impairment group, but there was no significant difference in tests on episodic memory and category verbal fluency between the 2 groups. Conclusion: Patients with mild cognitive impairment could be differentiated from cognitively normal controls, as well as from those with mild Alzheimer's disease, by neuropsychological measures. Key words: Alzheimer disease, Cognition Introduction Recently, the concept of mild cognitive impairment (MCI) has become increasingly popular. MCI is defined by subjective complaints of defective memory, abnormal memory functioning for age, normal performance of the activities of daily living, normal general cognitive functioning, and the absence of dementia. (1) The results of longitudinal studies on patients with MCI suggest that they 'convert' to Alzheimer's disease (AD) at a rate of 10% to 15% per year, whereas the conversion rate is 1% to 2% per year for the general elderly population. (1) This transitional state may be one of the optimum stages at which high-risk individuals can be identified for early intervention or preventive treatment. While there is good agreement for the concept of MCI, there is considerable variability concerning the validity of MCI as a cohesive clinical entity, the applicability of the research-based concept in clinical practice, the homogeneity of cognitive deficits in MCI, and the prognosis. (1,2) Although researchers have focused on patients with MCI with relatively isolated memory deficits, increasing numbers of studies have shown that performance in cognitive domains other than memory may not be entirely normal. (3-5) Indeed, current studies suggest that there are 2 forms of MCI, one with predominant impairment of memory and the other with a wider range of cognitive impairments. (1) Population studies have shown that the patients with predominant memory impairment constitute a relatively small group compared with all individuals with a much broader form of mild cognitive deficit. (6,7) Although the MCI syndrome is based on a neuropsychological pattern of impaired and non-impaired functions, there are still some discrepancies over how to classify these patients. The criteria for MCI subtypes proposed by Petersen do not specify the particular neuropsychological tests and their associated cut-off scores for case definition. (1) Detailed neuropsychological data can identify individuals experiencing mild or even unrecognised cognitive impairment in the primary care setting who are at a greater risk for developing AD. However, excessive reliance on neuropsychological data in the absence of the judgement of clinicians can lead to exaggerated inclusion of patients into the MCI cohort, and therefore affect the stability of the diagnosis and the reliability of the progression of the patients over time. (8) In this study, the subscale of the Clinical Dementia Rating (CDR) was used to define single-domain and multiple-domain MCI in patients satisfying the criteria for questionable dementia. …