Sex-Related Differences in Vascular Function Among Older Adults with Obstructive Sleep Apnea
Authors: Mazzone Josie L. , Tavoian Dallin , Bailey E. Fiona 
Published: May 2024

Obstructive sleep apnea (OSA) is a sleep disorder associated with hypertension and cardiovascular disease (CVD) risk. Endothelial dysfunction and altered shear stress are implicated in OSA-related CVD pathogenesis, however, their contributions to CVD risk in males vs females remains unclear. We obtained measures of resting blood pressure (BP), brachial artery flow-mediated dilation (FMD), brachial artery diameter, and shear stress in 71 older adults (F=30, M=41; age=66.9±7.7) diagnosed with mild, moderate, or severe OSA based on oxygen desaturation index (ODI) score. All were prospective participants in an ongoing clinical trial (NCT04932447). Group differences (mean ± SD) were assessed with two-way ANOVAs (sex X severity) and associations between ODI score, baseline diameter, relative FMD, shear stress, and BP were assessed with Pearson correlations. We hypothesized that a) regardless of sex, individuals with greater OSA severity exhibit lower relative FMD and mean shear stress, greater baseline diameter and higher BP, and b) for a given OSA severity, females have greater relative FMD and mean shear stress and lower baseline diameter and BP compared to males. In line with our hypotheses, we found greater mean shear stress in females compared to males (F=69.6±26.9 s−1, M=53.5±16.7 s−1, p=0.035) and among females, those with mild OSA had higher mean shear stress than those with severe OSA (mild=77.6±26.1 s−1, severe= 44.4±8.5 s−1, p=0.009). Contrary to expectations, mean shear stress did not differ as a function of OSA severity in male subjects, nor was there any difference in FMD or BP across OSA severity between males and females. In subjects with moderate OSA, FMD was greater in females than males (F=6.07±3.89%, M=3.07±2.39%, p=0.047). On average, baseline diameters were larger in adults with severe OSA compared to moderate OSA (moderate=3.66±0.59 mm, severe=4.33±0.61 mm, p=0.003), and females with mild (F=3.20±0.47 mm, M=4.73±0.50 mm, p<0.001) and moderate (F=3.31±0.42 mm, M=3.91±0.57 mm, p=0.007) OSA had smaller baseline diameters than their male counterparts. There were no differences in baseline diameter between males and females with severe OSA. We report a negative correlation between mean shear stress and BP (systolic BP, r=-0.48, p=0.011; diastolic BP, r=-0.55, p=0.002) and a positive correlation between ODI score and baseline diameter (r=0.54, p=0.003) in females but not males. Conversely, ODI score and relative FMD were positively correlated in male subjects (r=0.45, p=0.009), but not females. Overall, our findings highlight sex-specific vascular differences in older adults with OSA. Relative to males, females with mild OSA exhibit greater mean shear stress and lower baseline diameters, which may confer a cardiovascular advantage. In contrast, males and females with severe OSA exhibit similar vascular characteristics. Our findings provide new insights into the impact of sex and OSA severity on vascular function and CVD risk in older adults. This work is supported by NIH/NIA grant number: 1R01AG065346. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.