BACKGROUND: Subjective cognitive decline (SCD) is a risk factor for future cognitive impairment and dementia. It is uncertain whether the neurodegeneration of the cholinergic system is already present in SCD individuals. We aimed to review the current evidence about the association between SCD and biomarkers of degeneration in the cholinergic system. METHOD: Original articles were extracted from three databases: Pubmed, Web of Sciences, and Scopus, in January 2023. Two researchers screened the studies independently. RESULTS: A total of 11 research articles were selected. SCD was mostly based on amnestic cognitive complaints. Cholinergic system biomarkers included neuroimaging markers of basal forebrain volume, functional connectivity, transcranial magnetic stimulation, or biofluid. The evidence showed associations between basal forebrain atrophy, poorer connectivity of the cholinergic system, and SCD CONCLUSIONS: Degenerative changes in the cholinergic system can be present in SCD. Subjective complaints may help when identifying individuals with brain changes that are associated with cognitive impairment. These findings may have important implications in targeting individuals that may benefit from cholinergic-target treatments at very early stages of neurodegenerative diseases.

Department of Cybernetics Faculty of Electrical Engineering Czech Technical University Prague Prague Czech Republic; Department of Biomedical Engineering and Assistive Technology Czech Institute of Informatics Robotics and Cybernetics Czech Technical University Prague Prague Czech Republic; Department of Neurobiology Care Sciences and Society Karolinska Institutet Stockholm Sweden; Center for Alzheimer Research Stockholm Sweden; Division of Clinical Geriatrics Care Sciences and Society Karolinska Institutet Stockholm Sweden

Department of Neurobiology Care Sciences and Society Karolinska Institutet Stockholm Sweden; Center for Alzheimer Research Stockholm Sweden; Division of Clinical Geriatrics Care Sciences and Society Karolinska Institutet Stockholm Sweden

Department of Neurobiology Care Sciences and Society Karolinska Institutet Stockholm Sweden; Center for Alzheimer Research Stockholm Sweden; Division of Clinical Geriatrics Care Sciences and Society Karolinska Institutet Stockholm Sweden; Department of Neuroimaging Centre for Neuroimaging Sciences Institute of Psychiatry Psychology and Neuroscience King's College London London UK

Department of Psychology Faculty of Health Sciences University Fernando Pessoa Canarias Santa María de Guia Spain

Department of Psychology Faculty of Health Sciences University Fernando Pessoa Canarias Santa María de Guia Spain; Department of Psychology Sensory Cognitive Interaction Laboratory Stockholm University Stockholm Sweden; Department of Neurobiology Care Sciences and Society Karolinska Institutet Stockholm Sweden; Center for Alzheimer Research Stockholm Sweden; Division of Clinical Geriatrics Care Sciences and Society Karolinska Institutet Stockholm Sweden

Department of Psychology Sensory Cognitive Interaction Laboratory Stockholm University Stockholm Sweden

Department of Radiology Mayo Clinic Rochester MN USA

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