Objectives Depressive symptoms and cognitive impairment often concur in older persons. Differentiating the cause of cognitive impairment in older persons with Depressive Disorder (DD) from other diseases such as Alzheimer's Disease (AD) is challenging. The goal of this study was to characterize cognitive impairment in older persons with DD. Design Cross-sectional retrospective observational clinical cohort study using patient records from 2014 to 2018. Setting Gerontopsychiatric services of Ulm University at Bezirkskrankenhaus Gü nzburg serving as primary psychiatric care institution and tertiary referral center for psychiatric care for older persons. Partcipants DD was diagnosed according to ICD-10 criteria. When indicated by the medical history or neuropsychological assessment further diagnostic procedures were initiated. Cerebrospinal fluid (CSF) tap was routinely the first additional procedure. If patients did not consent to CSF tap or contraindications were present, 18 F-fluordesoxyglucose-PET (FDG-PET) or Amyloid-PET (Am-PET) were performed. Materials and methods Extensive neuropsychological test battery to assess cognitive profile. Results 457 subjects were diagnosed with DD (DD-all; age 50-94; 159 males, 298 females). Biomarkers were assessed in 176 persons; in 90 of these subjects AD-biomarkers were negative (DD-BM-; age 54-89; 40 males, 50 females), and in 86 subjects at least one biomarker

Alzheimer’s disease and depressive disorder are frequent in old age. Both may be associated with depressed mood and cognitive impairment. Therefore, finding a strategy to clarify the diagnosis underlying subjective complaints of impaired cognition and depressed mood in older persons is of utmost interest. We conducted a cross-sectional retrospective observational clinical cohort study using patient records from 2014 to 2018. From 3758 patients, we included patients aged 60 years and older with a Mini-Mental-Status Examination score of 24 and above. Final analysis included all patients in whom Alzheimer’s disease biomarker analysis was performed (CSF markers of Alzheimer’s disease or PET imaging; n = 179) and patients with depressive disorder in whom Alzheimer’s disease was ruled out by analysis of biomarkers suggestive of AD (n = 70). With case-control matching for age, education and gender, performance of patients with Alzheimer’s disease was worse in acquisition, consolidation and recall of verbal information and false positive answers. None of the results, however, sufficed to differentially diagnose individual patients with Alzheimer’s disease or depressive disorder. With more severe symptoms of depression, patients with biomarker-verified Alzheimer’s disease performed worse in executive testing but were not additionally impaired in verbal episodic memory performance. We conclude that distinguishing between Alzheimer’s disease and depressive disorder is unreliable on clinical grounds and behavioral testing alone. Diagnosing the cause of subjective complaints about deteriorating cognitive function or depressed mood requires additional biomarker assessment, whereas cognitive assessment is needed to define appropriate targets of symptomatic treatment in patients with Alzheimer’s disease and depressive disorder.