Alzheimer's disease biomarkers in different deffinitons ofsubjective cognitive decline

the emergence of the clinical symptoms in Alzheimer's Disease (AD) patients. For early diagnosis, pre-dementia clinical stages were identified. Subjective Cognitive Impairment refers to a clinical state of which no objective neuropsychological impairment is observed in individuals with cognitive complaints. Currently there is no consensus on the operationalization of SCD criteria. The aim of this study is to assess structural neuroimaging biomarkers of AD in different definitions of SCD. The study included 101 participants over 55 years of age, with memory complaints and no identifiable impairment in the Modified Mini Mental Test. We evaluated whether (i) using a valid scale (Subjective Memory Complaints Questionnaire-SMCQ) rather than a single question; (ii) utilizing neuropsychological test data in addition to a screening test; (iii) evaluating SCD + criteria –additional qualitative features of the complaintand (iv) the exclusion of comorbidities that may be associated with memory complaints; would be associated with increased atrophy in AD-related areas. Three different cortical thickness and two cortical volume patterns were determined as the dependent variables. Results suggested that age, sex, age of onset of memory complaints, depression or anxiety symptoms and vitamin B12 and vitamin D levels were associated with alterations in the structural markers of AD. Regarding different definitions of SCD; assessment of SCD + criteria, utilizing SMCQ, addition of neuropsychological test data and excluding individuals with comorbidities did not contribute to the validity of SCD in terms of the AD morphology. Our findings indicate the importance of psychiatric evaluation in individuals with subjective memory complaints. The presence of depression and anxiety symptoms in a person with SCD may increase the likelihood of AD-related brain morphological changes. Longitudinal studies, better assessment of the phenotype, inclusion of different diagnostic groups may help to refine the definition of SCD and the addition of criterion which may point to early morphological changes.