Obstructive sleep apnea is linked to cardiovascular disease, metabolic disorders and
dementia. The precise nature of the association between respiratory events in obstructive
sleep apnea, cortical or subcortical arousals, and cognitive, autonomic and oxidative
stress consequences remains incompletely elucidated. Previous studies have aimed to
understand the relationship between obstructive sleep apnea and arousal patterns,
as defined by the cyclic alternating pattern, but results have been inconsistent,
in part likely due to the presence of associated comorbidities. To better define this
relationship, we analysed cyclic alternating patterns in patients with obstructive
sleep apnea without any additional comorbidities. We identified 18 adult male, non-obese
subjects with obstructive sleep apnea and no other comorbidities or medication history,
who underwent whole-night electroencephalography and polysomnography. Cyclic alternating
pattern analysis was performed and verified by certified somnologists. Pairwise linear
regression analysis demonstrated an inverse relationship between obstructive sleep
apnea severity and cyclic alternating pattern subtype A1, and a direct correlation
with cyclic alternating pattern subtype A3. Cyclic alternating pattern subtypes A1
prevail in milder obstructive sleep apnea phenotype, whilst cyclic alternating pattern
subtypes A2 and A3 overcome among moderate-to-severe obstructive sleep apnea patients.
The milder obstructive sleep apnea group also presented higher sleep efficiency, and
increased percentages of non-rapid eye movement stage 3 and rapid eye movement sleep,
as well as longer cyclic alternating pattern sequences in N3, while severe obstructive
sleep apnea patients spent more time in lighter sleep stages. These results imply/suggest
a balance between cyclic alternating pattern's adaptive and maladaptive arousal processes
in obstructive sleep apnea of differing severities. In milder obstructive sleep apnea
(apnea-hypopnea index < 20), sleep continuity may be reinforced by cyclic alternating
pattern subtype A1, whereas in more severe obstructive sleep apnea, decompensation
of these sleep-stabilizing mechanisms may occur and more intrusive cyclic alternating
pattern fluctuations disrupt sleep circuitry.
