Associations of brain lesions at autopsy with polysomnography features before death

Objective: To determine how sleep-disordered breathing, nocturnal hypoxia, and changes in sleep architecture in the elderly may be related to the development of the neuropathologic correlates of dementia.

Methods: The Honolulu-Asia Aging Study is a prospective cohort study of Japanese American men in Honolulu, HI. We examined brain lesions at autopsy (Braak stage, neurofibrillary tangle and neuritic plaque counts, microinfarcts, generalized brain atrophy, lacunar infarcts, Lewy bodies [LBs], neuronal loss and gliosis in the locus ceruleus) in 167 participants who underwent polysomnography in 1999–2000 (mean age, 84 years) and died through 2010 (mean 6.4 years to death). Polysomnography measures included the apnea-hypopnea index, duration of apnea or hypopnea, duration of hypoxemia, minimum oxygen saturation (SpO₂), duration of slow-wave sleep (SWS, non-REM stage N3), and arousals.

Results: Sleep duration with SpO₂ <95% was associated with higher levels of microinfarcts (adjusted odds ratio [OR] 3.88, 95% confidence interval [CI] 1.10–13.76, comparing the highest to lowest quartiles of %sleep with SpO₂ <95%). Greater SWS duration was associated with less generalized atrophy (adjusted OR 0.32, 95% CI 0.10–1.03, comparing highest to lowest quartiles of %sleep in SWS). LBs were less common with greater %sleep with SpO₂ <95% (adjusted OR 0.17, 95% CI 0.04–0.78, comparing highest to lowest quartiles). Higher minimum SpO₂ during REM sleep was associated with less gliosis and neuronal loss in the locus ceruleus. Cognitive scores declined less among men with greater SWS duration.

Conclusions: The findings support a role for lower nocturnal oxygenation and SWS in the development of microinfarcts and brain atrophy, but not Alzheimer lesions or LBs.