Introduction: Wake-up stroke (WUS) may represent a specific subgroup and comprise of a quarter of all ischemic strokes. Nocturnal desaturation secondary due to sleep apnea is an independent risk factor for stroke, however, the association between nocturnal desaturation and WUS remains unclear.
Hypothesis: We assessed the relationship between the overnight oxygen desaturation index (ODI) and WUS in patients with acute stroke in the stroke unit.
Methods: A consecutive 225 patients with acute ischemic stroke who were admitted to the stroke unit within 7 days after stroke onset between July 2013 and June 2014 were included for analysis. Physiological variables including pulse oximetry were sampled every 1 minute. The ODI was calculated using pulse oximetry data during 9 hours on the first night (10:00 PM-7:00 AM) of the stroke unit admission and nocturnal oxygen desaturation was defined as an ODI of 5 or greater per hour. We compared the clinical characteristics, nocturnal oxygen desaturation, laboratory findings, and radiologic findings in patients with and without WUS.
Results: Among the total patients, 26.2% (n=59) patients had WUS. These patients were mostly male (52.4%), with a mean age of 66.8 years. The proportion of nocturnal desaturation was significantly greater in WUS compared to non-WUS (23.7% vs. 8.4%, P = 0.002). The age, gender, vascular risk factors, stroke severity, and stroke lesion locations were similar in the two groups (WUS and non-WUS). After controlling for relevant confounding factors, nocturnal oxygen desaturation in the first night of the stroke unit stay was significantly more common in patients with WUS (Odds ratio, 4.39; 95% confidence interval, 1.76-10.93).
Conclusions: Nocturnal desaturation was more frequently observed in patients with WUS over the first night stay in the stroke unit. This suggests that nocturnal desaturation is a possible and modifiable risk factor for the occurrence of WUS.