Cognitive and Neuroimaging Correlates of the Insomnia Severity Index in Obstructive Sleep Apnea: A Pilot-Study.

We aim to determine the sleep correlates of age-related brain loss in a sample of middle-aged to older males with obstructive sleep apnea (OSA). We recruited consecutive treatment naïve male patients with moderate to severe OSA from January to November of 2019. We excluded participants if they had dementia, stroke or heart disease. We collected demographic variables and vascular risk factors. We also obtained the insomnia severity index, the Epworth sleepiness scale and the Pittsburgh sleep quality index. We also obtained computerized neurocognitive testing with the go-no-go response inhibition test, Stroop interference test, catch game test, staged information processing speed test, verbal memory test and non-verbal memory test. We derived age and education adjusted domain-specific Z-scores for global cognition, memory, attention, processing speed and executive function. We used brain MRI T1-weighted images to derive total hippocampal and gray matter volumes. Partial correlations evaluated associations between variables from sleep questionnaires (e.g., insomnia severity index score), and polysomnographic variables (the apnea-hypopnea index, average oxygen levels during sleep) with cognitive domains and brain volumes. We examined 16 participants with an age range of 40-76 years, 73% Hispanic/Latino. The mean apnea-hypopnea index was 48.9 ± 25.5 and average oxygen saturation during sleep was 91.4% ± 6.9%. Hypertension was seen in 66% and diabetes mellitus in 27%. We found that the insomnia severity index score and average oxygen levels during sleep had the strongest correlations with brain volumes and cognition. These preliminary findings may aid in developing future strategies to improve age-related brain loss in patients with OSA.

Poor sleep is associated with small hippocampal subfields in cognitively normal elderly individuals.

Recent studies demonstrated reduced hippocampal volumes in elderly healthy individuals who are cognitively normal but poor sleepers. The association between sleep quality and the pattern of volume loss across hippocampal subfields (HSs) is not well known. Thus, it is the focus of the present study. Sleep quality was self-assessed using the Pittsburgh Sleep Quality Index (PSQI). The HS volumes were measured using sub-millimetre in-plane resolution T2-weighted magnetic resonance imaging data. A total of 67 cognitively normal elderly individuals aged 60-83 years were classified into 30 normal sleepers with a PSQI <5 and 37 poor sleepers with a PSQI ≥5. The two groups were equivalent in age, gender distribution, ethnicity, education attainment, handedness and cognitive performance. Compared to normal sleepers, poor sleepers exhibited significantly lower normalised volumes in the left cornu ammonis field 1 (CA1), dentate gyrus (DG) and subiculum. In contrast, there were no significant differences in normalised grey and white matter volumes between the two groups. The global PSQI was negatively associated with the normalised volumes of the left CA1, DG and subiculum. Sleep duration was associated with the normalised volumes of the bilateral CA1, DG, left CA2 and subiculum. Verbal memory scores were associated with the left CA1 volume. In conclusion, poor sleep quality, especially insufficient sleep duration, was associated with volume loss in several HSs that are involved in specific learning and memory tasks. As the hippocampus does not regulate sleep, it is more likely that poor sleep leads to small hippocampi. Thus, based on this assumption, improving sleep quality of poor sleeper elderly individuals could benefit hippocampal health.

Effect of sleep quality on amnestic mild cognitive impairment vulnerable brain regions in cognitively normal elderly individuals.

STUDY OBJECTIVES: This study aims to evaluate the extent to which sleep quality impacts amnestic mild cognitive impairment (aMCI)-related brain regions in a cognitively normal cohort of individuals. METHODS: Seventy-four participants were rigorously evaluated using a battery of cognitive tests and a detailed clinical assessment to verify normal cognitive status. We then screened for sleep quality using the Pittsburgh Sleep Quality Index (PSQI) and depressive symptoms using the Geriatric Depression Scale (GDS). Five subjects were excluded due to mild depression. Overall 38 individuals with mean age 70.7 ± 7 were classified as poor sleepers and 31 with mean age of 69.6 ± 6 years as normal sleepers. Structural MRI and Freesurfer brain parcellation were used to measure aMCI-related brain regions. RESULTS: Relative to normal sleepers, poor sleepers exhibited significant reductions in cortical and subcortical volumes bilaterally in the hippocampi, as well as in the superior parietal lobules and left amygdala. The effects were strongest in the left superior parietal lobule (p < .015), followed by the hippocampi. Diffuse patterns of cortical thinning were observed in the frontal lobes, but significant effects were concentrated in the right mesial frontal cortex. Lower sleep duration was most correlated with cortical volume and thickness reductions among all subjects. CONCLUSIONS: Atrophy related to poor sleep quality impacted a number of regions implicated in aMCI and Alzheimer's disease (AD). As such, interventions targeted towards improving sleep quality amongst the elderly may prove an effective tool for modulating the course of aMCI and AD.

Evaluating different aspects of prospective memory in amnestic and nonamnestic mild cognitive impairment.

Prospective memory, the inability to remember an intended action, is a common complaint, but not formally assessed in most clinical and research studies of mild cognitive impairment (MCI). In this study, patients with amnestic mild cognitive impairment (aMCI), non-amnestic cognitive impairment (naMCI), and cognitively normal (CN) elders were assessed using the Miami Prospective Memory Test (MPMT). A unique aspect of the paradigm was that participants were scored for intention to perform, accuracy in recollection for specific elements of the task, and the need for reminder cues. Excellent test-retest stability was obtained for MPMT Event-Related (ER), combined Time-Related (TR) subscales, and total MPMT score for aMCI subjects. MPMT impairments were observed in 48.6% of aMCI, 29.4% of naMCI, and 10.0% of normal elderly participants. Prospective memory deficits were common in participants with aMCI, and occurred in almost a third of naMCI participants. Intention to perform and need for reminder cues were significantly more impaired than retrospective memory for specific details of the task. It is concluded that assessment of different elements of prospective memory is important in MCI research and that inability to remember intended actions is a significant feature in those as risk for Alzheimer's disease.