Longitudinal study of two subtypes of mild cognitive impairment

Abstract

Objective To investigate the conversion rate of subtypes of amnestic mild cognitive impairment (aMCI) to Alzheimer' s disease (AD) and assess the contribution of neuropsychological disturbance in progression from MCI to AD over 2 years. Method Subjects from memory clinic of Huashan hospital including 130 of who met the operational criteria for Mayo Clinic defined aMCI by neuropsychological tests covering global cognitive function, executive function, memory function, language function and visual spatial skills. They underwent multidimensional assessment and a neuropsychological battery at baseline and at follow-up, after about 2 years. Diagnosis for dementia was based on National Institute of Neurological and Communicative Disorders and Stroke; Alzheimer' s Disease and Related Disorders Association (NINCDS-ADRDA) criteria. Results Forty-four cases of 130 (33. 8% ) elder people with aMCI converted to probable AD with 17 aMCI-s and 27 aMCI-m subjects within an average 23.8 (6. 8 ) months. There was significant difference between the reversion rate of aMCI-s and aMCI-m (26. 2% vs 42. 9%, x2 = 3.957,P = 0. 047). Moreover, as the disease progressing,the two groups declined similarly in memory and executive function while in the aMCI-s group, the function of spatial structure relatively reserved in aMCI-s but function of language and attention diminished faster, and in the aMCI-m group, the ability of spatial structure declined even more significantly. Conclusion The aMCI-m is more likely to progress to AD than aMCI-s and it' s necessary to divide aMCI into aMCI-s and aMCI-m to help determine prognosis. Key words: Cognition disorders; Alzheimer disease; Neuropsychological tests; Follow-up studies