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Wake-up strokes (WUS) account for ≈20% to 30% of ischemic strokes. Studies have shown that increased autonomic instability as measured by blood pressure variability (BPV) is greater in stroke patients than nonstroke patients, but no studies have compared BPV in WUS versus non-WUS patients.From a single-center prospective registry, we identified consecutive ischemic stroke patients. BPV was calculated as the coefficient of variation of the mean arterial pressure during the first 24 hours after hospitalization. We assessed 24-hour BPV as a continuous measure and in quartiles in WUS versus non-WUS patients using univariable and multivariable statistics.Among 369 patients (64.9±16.5 years; 50.1% male; 64.7% white), 78 were WUS (21.1%). Clinical characteristics and medical history were not different between WUS and non-WUS patients except WUS patients were older (69.0 versus 63.8 years; P=0.015) and more frequently had previous ischemic stroke (29.5% versus 17.2%; P=0.012). Initial 24-hour BPV (11.77 versus 10.76; P=0.098) was similar between groups. However, WUS patients had greater nocturnal BPV (10.50 versus 8.95; P=0.030), whereas daytime BPV was similar between groups (10.96 versus 10.47, P=0.459). In multivariate analysis, the highest quartile (≥11.48 mm Hg) of nocturnal BPV was independently associated with WUS (adjusted odds ratio, 1.95; confidence interval, 1.13–3.39; P=0.017).In this single-center study, we observed that greater nocturnal BPV during the first 24 hours after hospitalization occurred in WUS than non-WUS patients. Nocturnal autonomic instability warrants further study as a potential mechanism of WUS.