5-March-2013 - Probable amnestic MCI people are in the highest risk of conversion to dementia
People with probable amnestic mild cognitive impairment (MCI) have the most and closest risk of conversion to dementia, mainly Alzheimer’s disease (AD), according to a recent research of Fundació ACE, Barcelona Alzheimer Treatment and Research Center (www.fundacioace.com). That is, amnestic MCI subjects without any comorbidity that could explain their cognitive deficits have 8.5 times more risk to convert to dementia than people with non-amnestic MCI caused by cerebrovascular pathology or psycho-affective symptoms. Furthermore, a storage pattern of memory impairment, the multiple domain condition, and the presence of at least one ε4 allele increase the risk of conversion to dementia in MCI subjects.
The study reports one of the largest single-site clinical MCI series reported worldwide: a five-year longitudinal follow-up of 550 MCI subjects, undertaken and led by Fundació ACE, Barcelona Alzheimer Treatment and Research Center. All individuals had a Clinical Dementia Rating scale of 0.5, they were older than 60 years old, and their DNA was available.
Therefore, MCI cases were divided into probable amnestic (Pr-aMCI, n = 115), probable non-amnestic (Pr-naMCI, n = 37), possible amnestic (Pss-aMCI, n = 234), and possible non-amnestic (Pss-naMCI, n = 164), single or multiple domain. A total of 257 (46.7%) subjects developed dementia during the five-year follow-up research. Vall d’Hebron Institute of Research (VHIR) and the University of Pittsburgh Alzheimer Disease Research Center (ADRC) collaborated in the analysis and the interpretation of the results. “Espinosa et al. paper is the first study that analyzes the non-amnestic group with or without comorbidities to increase the accuracy of the MCI classification”, says doctor Montserrat Alegret, Neuropsychology Chief of Fundació ACE.
The study determined which neuropsychological test performances, including episodic memory profiles, and genetic risk factors (APOE ε4) better predict early conversion to dementia among the four MCI subtypes. For the whole MCI group, neuropsychological assessment demonstrated that Orientation, Verbal Delayed Recall and visuospatial functions are of great importance in the conversion to dementia, independently of APOE ε4.
The most recent studies about MCI are focused on the search for risk factors that make patients more vulnerable to conversion to dementia, mainly AD. The results allow estimating the conversion rates from a MCI type to dementia. Moreover, “this new classification identifies probable amnestic MCI people as a new target for future AD clinical trials. In the clinical practice, neuropsychological testing is the most cost-effective and may be the most sensitive method to assess the early impaired brain functions in a Memory Clinic Diagnostic Unit”, concludes Ana Espinosa, first author of the study.
Scientific article in Espinosa A, Alegret M, Valero S, Vinyes-Junqué G, Hernández I, Mauleón A, Rosende-Roca M, Ruiz A, López O, Tárraga L, Boada M.A longitudinal follow-up of 550 mild cognitive impairment patients: Evidence for large conversion to dementia rates and detection of major risk factors involved. J Alzheimers Dis. 2013; 34(3). DOI: 10.3233/JAD-122002