Tau Accumulation and Dopamine Transporter Availability in Elderly Adults with Depression

Background: Depression in later life is associated with dopaminergic dysfunction and increased risk of neurodegenerative disorders, although the relationship between dopamine transporter (DAT) availability and tau accumulation remains unclear. Although previous studies have linked tau and DAT in neurodegenerative diseases, evidence related to depression is limited. Therefore, this study used positron emission tomography (PET) to investigate the association between tau pathology and DAT availability in elderly adults with depression. Methods: Six patients diagnosed with depression according to ICD-10 criteria underwent PET scans with PET radioligands that enable accurate in vivo assessment, namely, florzolotau (18F) for tau and [^18F]FE-PE2I for DAT. Clinical assessments using the Mini-Mental State Examination (MMSE) and Hamilton Depression Rating Scale (HAM-D) were performed for all patients. Tau standardized uptake value ratios (SUVR) in the striatal and cortical regions and DAT binding potentials (BP_ND) in the striatum were calculated. Results: Tau SUVR in all regions was negatively correlated with DAT BP_ND in the striatum, suggesting that greater tau burden may be linked to dopaminergic dysfunction. Tau SUVR in the striatum was negatively correlated with MMSE, indicating that tau accumulation may be related to subtle cognitive decline. DAT BP_ND in the striatum was not correlated with HAM-D. Conclusions: These preliminary results suggest a link between tau pathology and dopaminergic dysfunction in elderly adults with depression.