Reduced cortical arousability to nocturnal apneic episodes in patients with wake-up ischemic stroke

Sleep breathing disorders (SBD) have been linked to wake-up stroke (WUS). Respiratory arousals have an important role in responding to danger during sleep, yet currently no studies have investigated respiratory arousability in WUS. In this study, we used a clinical tool to predict low respiratory arousal threshold (ArTH), and then compared respiratory arousability in patients with WUS and non-WUS.

We enrolled 119 patients with acute ischemic stroke and assigned them into WUS (n = 34) and non-WUS (n = 85) groups. All participants underwent polysomnography (PSG) during the acute phase of stroke. The respiratory ArTH predictive tool assigns one point for each of the following: apnea-hypopnea index (AHI) < 30/h, nadir oxygen saturation (SaO₂) > 82.5%, and fraction of hypopneas > 58.3%. An ArTH score ≥2 represents low respiratory ArTH.

Our results reconfirmed the association between moderate-to-severe sleep apnea syndrome and WUS (OR 2.879, 95% CI 1.17-7.089, p = 0.021). Significantly fewer participants with obstructive sleep apnea (AHI ≥ 5/h) had low respiratory ArTH in the WUS group than in the non-WUS group (34.8% vs. 68.1%, respectively, p = 0.008). High respiratory ArTH was independently associated with WUS (OR 5.556, 95% CI 1.959-15.761, p = 0.001).

The correlation between SBD and WUS suggests that sleep apnea might induce acute physiological changes that trigger the onset of stroke. We show that reduced respiratory arousability is associated with WUS, and hypothesize that reduced cortical capability to generate respiratory arousal may have a role in triggering stroke during sleep.