Conversion of amnestic Mild Cognitive Impairment to dementia of Alzheimer type is independent to memory deterioration.

BACKGROUND: Mild Cognitive Impairment defines a transitional stage between normal ageing and dementia, and reflects the clinical situation where a person has memory complaints and objective evidence of cognitive impairment but no evidence of dementia. To plan the care of patients with MCI, it is important to predict as accurately as possible potential risk factors modulating the conversion to AD.

AIM: To investigate the risk factors associated of conversion to dementia of Alzheimer type (AD) for subjects with amnestic Mild Cognitive Impairment (aMCI).

METHODS AND MATERIALS: One hundred nineteen subjects consecutively recruited who met the operational criteria for aMCI (with or without deficits in other cognitive domains). They underwent multidimensional assessment and a neuropsychological battery at baseline and at follow-up, after 1 year. Diagnosis for dementia was based on a deficit in two or more cognitive domains severe enough to affect the participant functional abilities. Subjects converted to AD over time were classified as Demented; subjects that remained unchanged, or became cognitively normal during follow-up, were defined as Stable.

RESULTS: Demented MCI (N = 40; 33.6%) were older (mean age 73.5 +/- 8.5 vs. 69.2 +/- 7.0; p = 0.006) when compared to Stable (N = 79; 66.4) and their global cognitive performances, at baseline, were more compromised when assessed by ADAS-Cog (mean score 10.7 +/- 3.9 vs 6.7 +/- 3.4; p = .000) and by MMSE (mean score 26.1 +/- 1.9 vs. 27.3 +/- 1.8; p = 0.002). Demented were similarly compromised in basic activities of daily living (BADL mean 0.2 +/- 0.4 vs 0.1 +/- 0.3 functions lost; p = NS) but more compromised on instrumental daily functions (IADL mean 0.7 +/- 0.8 vs. 0.1 +/- 0.5 functions lost; p = 0.001). The presence of white matter lesions (WML) on CT or MRI was more pronounced in Demented group (p = 0.02). After 1 year; Demented worsened on phonemic verbal fluency (PFL) (p = 0.009), Raven's coloured matrices (p = 0.003), Trail Making test A and B (p = 0.008 and p = 0.007 respectively) and in Instrumental Activities of Daily Living (IADL) (p =0 .000) respect to Stable. Logistic regression analysis revealed that ADAS-Cog basal score, Trail Making B, IADL but not memory deterioration were significantly associated to the conversion to AD.

CONCLUSIONS: In subjects with aMCI poor global cognitive performance at baseline, the worsening on executive functions and on functional status but not the worsening on memory functions are independently associated with the conversion to dementia of Alzheimer type at 1 year, follow-up.