Sleep-disordered breathing (SDB) is a potential predictor of worsened functional outcomes at 3 months after noncardioembolic ischemic stroke, according to study results published in Stroke.
Cardiopulmonary coupling (CPC) analysis, a technology that provides several important indicators of sleep, was recently reported to be a good predictor of SDB. Previous studies have shown that SDB at the early stages of ischemic stroke is associated with increased risk for adverse clinical outcomes. SDB associated with Narrow-band (NB) coupling, a type of elevated low-frequency coupling, was found to be associated with a higher incidence of risk factors for ischemic stroke.
The goal of the current study was to assess the effect of SDB, defined by CPC analysis using Holter monitoring, on the functional outcomes at 3 months after ischemic stroke according to the modified Rankin Scale (mRS).
The study population consisted of 615 patients (mean age, 64.5 years) from the Korea University Stroke Registry, a multicenter, prospective cohort that includes all patients with acute ischemic stroke. All study participants underwent Holter monitoring during the acute phase of stroke.
Evidence for NB coupling during sleep time was documented in 191 (31.1%) study participants, while unseen in 424 participants. Participants with evidence for NB coupling were significantly older (68.9 y vs 62.5 y, respectively; P <.001), and had a higher prevalence of prior stroke (17.2% vs 7.3%, respectively; P <.001) and hypertension (68.5% vs 54.4%, respectively; P =.001).
Moderate to severe functional impairment at 3 months after ischemic stroke, defined as mRS score >2, was significantly more common in patients with evidence for NB coupling compared with those in the non-NB group (45.5% vs 12.9%, respectively; odds ratio [OR], 5.61; 95% CI, 3.75-8.38; P <.001). Similarly, the former group had a higher rate of persistent functional impairment (53.9% vs 39.8%; OR, 1.76; 95% CI, 1.25-2.49; P<.001).
Multivariate analysis identified NB coupling as an independent predictor of worsened functional outcomes 3 months after an ischemic stroke, with an increased risk for moderate to severe functional impairment (OR, 3.98; 95% CI, 2.34-6.78; P <.001) and persistent functional impairment (OR, 1.81; 95% CI, 1.23-2.66; P =.002).
The results were consistent in a propensity-score matching analysis that included 157 patients with NB coupling and a similar number of subjects without NB coupling during sleep (C-statistic=.770).
Furthermore, the risk for moderate to severe functional impairment and persistent functional impairment at 3 months was greater in patients with increased rate of NB coupling (>10% and ≤10%), compared to those in the non-NB group.
The study had several limitations, such as the nonrandomized design affecting differences between study groups at baseline. Other limitations included the relatively small sample size, exclusion of patients with cardioembolic stroke as CPC analysis is only accurate with normal sinus rhythm, and the use of telephone interviews as many patients were unable to visit the clinic at 3 months.
“CPC analysis,” concluded the researchers, “using Holter monitoring is a useful modality for predicting functional impairment in acute ischemic stroke.”
Kang DO, Kim CK, Park Y, et al. Impact of sleep-disordered breathing on functional outcomes in ischemic stroke: a cardiopulmonary coupling analysis [published online June 9, 2020]. Stroke. doi:10.1161/STROKEAHA.119.028730