Tau deposition in the locus coeruleus and depression in cognitively unimpaired older adults

Abstract

Background Depression is a common manifestation of Alzheimer’s disease (AD) and frequently observed at the early phase of the disease. Several postmortem studies demonstrated that tau deposition was found at the brainstem nuclei including the locus coeruleus (LC) and dossal raphe nucleus (DRN) (3, 4), even before early Braak stages of neurofibrillary tangle pathology. Given the disturbance of monoaminergic system is related to depression in general, tau deposition in the LC or DRN may underlie depression in late‐life, as suggested in a couple of postmortem studies. In this context, we tried to examine the hypothetical association between in vivo tau depostion at the brain stem monoaminergic nuclei and depression in cognitively unimpaired older adults. Method A total of 69 cognitively unimpaired older adults from the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer’s Disease (KBASE) were included. All participants underwent comprehensive clinical assessment including the Hamilton Rating Scale for Depression (HRSD) and [18F] AV‐1451 positron emission tomography. Tau deposition in the LC and DRN was measured using the Harvard Ascending Arousal Network Atlas (AAN). Tau deposition in the pons was also assessed as a non‐monoaminergic control for comparison. Age, education, sex, and apolipoprotein E ε4 positivity were controlled as covariates in the analyses for the association between brain stem tau and HRSD score. Result Tau deposition in the LC was significantly associated with HRSD total score (β = 3.861, P = .009). In contrast, there was no significant association between tau deposition in the DRN and HRSD score (β = 2.229, P = .090). Tau deposition in the pons was also not related to HRSD score (β = 1.632, P = .207). Conclusion The findings support the possibility that alteration of the noradrenergic neurons in the LC by tau pathology may underlie depressive manifestation in cognitively unimpaired older individuals.