Mild cognitive Impairment: Risk of Dementia according to Subtypes

Abstract

Mild cognitive impairment (MCI) has 3 clinical subtypes: amnestic (aMCI), multiple domains (mdMCI) and non-amnestic single domain (na-SD-MCI) whose evolutive possibility to dementia has not been profoundly studied.

Objective: This paper aims to determine the conversion to dementia of the different subtypes of MCI and determine risk factors associated to conversion to dementia.

Methods: A total of 127 patients diagnosed with MCI (age=70.21; SD=13.17) were evaluated with a neuropsychological and neuropsychiatric battery. They were classified into 3 groups: amnestic MCI (n=20), multipledomain MCI (n=98), non-amnestic MCI (n=9). Seventeen normal subjects (age=74.59; SD=10.63) were included.

Results: Of those included, 27.1% developed Alzheimer’s type dementia [average time for conversion to Alzheimer’s dementia (AD) 11.12 months (SD=0.183)]. None of the controls developed dementia. Thirty-five percent (n=7) of amnestic MCI converted to AD: 20% (n=4) at 6 months and 15% (n=3) at 12 months); 11.1% (n=1) of the non-amnestic single domain MCI converted to AD at 6 months. It was found that 31.6% (n=31) of multiple domain MCI rotated to AD: 15.3% (n=15) at 6 months and 16.3% (n=16) at 12 months. Age (p<0.05, β=1.03) increased the likelihood of rotation to AD. Multi-domain MCI subtype was the most frequent. However, the conversion to dementia in amnestic subtype was the highest, age and retirement being the variables that increased the likelihood of conversion to Dementia.