Association of Polysomnographic Sleep Parameters With Neuroimaging Biomarkers of Cerebrovascular Disease in Older Adults With Sleep Apnea

Background and Objectives:Our objective was to determine whether polysomnographic (PSG) sleep parameters are associated with neuroimaging biomarkers of cerebrovascular disease (CVD) related to white matter integrity in older adults with obstructive sleep apnea (OSA).Methods:From the population-based Mayo Clinic Study of Aging, we identified participants without dementia who underwent at least one brain MRI and PSG. We quantified two CVD biomarkers: white matter hyperintensities (WMH) from FLAIR-MRI and fractional anisotropy of the genu of the corpus callosum (genu FA) from diffusion MRI. For this cross-sectional analysis, we fit linear models to assess associations between PSG parameters (N1%, N3% [slow-wave sleep], mean oxyhemoglobin saturation, and log of apnea-hypopnea index [AHI]) and CVD biomarkers (log of WMH and log of genu FA), respectively, while adjusting for age (at MRI), sex, APOε4 status, composite cardiovascular and metabolic conditions (CMC) score, REM stage percentage, sleep duration, and interval between MRI and PSG.Results:We included 140 participants with FLAIR-MRI (of which 103 had additional diffusion MRI). The mean ± s.d. age was 72.7 ± 9.6 years old at MRI with nearly 60% being men. The absolute median (IQR) interval between MRI and PSG was 1.74 (0.9 – 3.2) years. 90.7% were cognitively unimpaired during both assessments. For every 10-point decrease in N3%, there was a 0.058 (95% CI 0.006 to 0.111, p=0.030) increase in the log of WMH and 0.006 decrease (95% CI -0.012 to -0.0002, p=0.042) in the log of genu FA. After matching for age, sex, and N3%, participants with severe OSA had higher WMH (median [IQR] 0.007 [0.005 to 0.015] vs. 0.006 [0.003 to 0.009], p=0.042) and lower genu FA (median [IQR] 0.57 [0.55 to 0.63] vs. 0.63 [0.58 to 0.65], p=0.007), when compared with those with mild/moderate OSA.Discussion:We found that reduced slow-wave sleep and severe OSA were associated with higher burden of white matter abnormalities in predominantly cognitively unimpaired older adults, which may contribute to greater risk of cognitive impairment, dementia, and stroke. Our study supports the association between sleep depth/fragmentation and intermittent hypoxia and CVD biomarkers. Longitudinal studies are required to assess causation.