MRI-Based Investigations of Brain Structure and Cerebral Blood Flow and Their Associations with Sleep Quality and Cognitive Performance in the Aging Brain

Abstract

Population aging leads to increased prevalence of age-related cognitive decline and dementia. Identifying factors that accelerate brain aging in older adults is crucial to mitigate their impacts on the brain.Sleep is vital to brain health. Our cross-sectional study showed that the left cornu ammonis field 1, left dentate gyrus, and left subiculum contributed the most to the decrease of hippocampal volume in poor sleepers relative to normal sleepers, and the sleep quality was associated with these hippocampal subfields. Our longitudinal study showed that poor sleep quality accelerated rates of volume loss primarily in the right hippocampus (over 3-fold) and right posterior cingulate (over 5-fold).Reduced cerebral blood flow (CBF) and increased brain atrophy are two AD biomarkers. In early amnestic mild cognitive impairment (aMCI), our study found that reduced CBF but no tissue loss in the AD-prone brain regions compared to cognitively normal. Thereby, reduced CBF precedes brain tissue loss and is a more sensitive biomarker of early aMCI.Investigating sex differences in brain volumes, CBF, cognition and their interrelationships can help elucidate sex differences in brain aging. In our study of the oldest-old cognitively normal individuals (aged 85+), 23 brain regions occupied a larger portion of the intracranial space in women than in men. With similar total CBF as men, women had higher global cerebral perfusion. Volumes of more brain regions were associated with cognition in women than in men, while total CBF was associated with cognition only in women. Therefore, women are more vulnerable to reduction in CBF than men, and are more prone to cognitive decline, as total CBF declines with age. Clearly, the women's brain is not a smaller version of the men's brain