Witnessed apneas are associated with elevated tau-PET levels in cognitively unimpaired elderly

Objective: To assess whether informant-reported apneas during sleep
(witnessed apneas) in cognitively unimpaired (CU) elderly persons are
associated with higher levels of brain tau. Methods: From the
population-based Mayo Clinic Study of Aging, we identified 292 CU elderly
aged >=65 years with both AV-1451 tau-PET and PiB-PET scans and
whose bed partners and close relatives had completed a questionnaire that
assessed whether participants had witnessed apneas during sleep. For this
cross-sectional analysis, we selected the entorhinal and inferior temporal
cortices as our regions of interest (ROI), because they are highly
susceptible to tau accumulation. PET signal was scaled to the cerebellum
crus to calculate standardized uptake value ratio (SUVR). We fit linear
models to assess the association between regional tau and witnessed
apneas, while controlling for age, sex, years of education, body mass
index, hypertension, hyperlipidemia, diabetes, reduced sleep, excessive
daytime sleepiness, and global PiB. Results: 43 participants (14.7%) were
found to have witnessed apneas during sleep. The report of witnessed
apneas was associated with higher tau-PET SUVR elevation in our
ROIs:  0.049 SUVR (95%CI: 0.010 – 0.087, p=.015) in the
entorhinal cortex and 0.037 SUVR (95% CI: 0.007 – 0.067, p=.019) in the
inferior temporal cortex, after controlling for confounders. Conclusions:
We identified a significant association between witnessed apneas in CU
elderly and elevated tau-PET signal in tau-susceptible brain regions.
These results suggest a plausible mechanism that could contribute to
cognitive impairment and the development of Alzheimer’s disease.
Longitudinal observations will be necessary to determine direction of
causality.