Microvascular Disease in the Hippocampus in Obstructive Sleep Apnoea

Ischemia is a primary cause of microvascular disease, particularly in the hippocampus, which is unusually vulnerable to hypoperfusion and hypoxia. Since intermittent hypoxia is a defining feature of obstructive sleep apnoea (OSA), the present study examined microvessels in autopsy tissue from patients with clinically confirmed OSA. Immunohistochemistry was performed on 30 hippocampal autopsy samples to investigate whether the incidence of microvascular abnormalities is associated with increased OSA severity, and if so, whether regular use of continuous positive airway pressure (CPAP) is protective. There were significantly more string vessels (4.3 ± 0.9 vs. 1.7 ± 0.4, p = 0.014), narrowing vessels (3.5 ± 1.0 vs. 0.9 ± 0.3, p = 0.024), strictures (2.6 ± 0.4 vs. 1.1 ± 0.2, p = 0.002) and total abnormalities (10.3 ± 1.5 vs. 3.7 ± 0.6, p = 0.001) in the CA1 subregion of the moderate-severe OSA group (mean ODI 35.9 ± 6.4 events/h sleep) than in the mild-moderate OSA group (mean ODI 18.5 ± 3.7 events/h sleep). There were no significant differences between regular CPAP users and non-CPAP users, or between younger and older individuals. We conclude that in moderate-severe OSA, the preponderance of microvascular abnormalities in the CA1, which are too narrow to carry blood, amplify its vulnerability to ischemia.