We identified 1,778 adult area residents, with 1,854 first-ever and recurrent ischemic strokes that were first evaluated in an ED in 2005; 273 wake-up strokes (14.3%, 95% confidence interval [CI] 12.7–15.9) occurred in 271 subjects. Seventy-three patients had more than one stroke identified during 2005; 70 patients had 2 strokes reported during the year and 3 patients had 3 strokes. Eighteen patients had both a wake-up stroke and a non-wake-up stroke during the year. The exact times of stroke onset and arrival to the ED were recorded for 637 non-wake-up strokes, of which 428 presented to the ED within 3 hours of onset and 209 presented beyond 3 hours of stroke onset. Of the 944 non-wake-up strokes without a documented time of onset to arrival, 362 had an estimated time of stroke in one of the 6-hour windows, 358 presented to the ED greater than 24 hours after onset, 219 had no estimate of stroke onset, and 5 had no recorded time of arrival to the ED. There were 11 cases ascertained through out-of-hospital surveillance. The adjusted event rate of wake-up strokes presenting to an ED was 26.0/100,000 (95% CI 22.9–29.1).
A comparison of the baseline characteristics of wake-up stroke patients with all others is found in . Compared with the non-wake-up stroke group, wake-up stroke patients were older (72.3 ± 0.83 years vs 70.0 ± 0.48 years; p = 0.01) and had higher baseline rNIHSS scores (median [IQR] = 4 [2, 8] vs 3 [2, 7]; p = 0.004). There were no differences between the groups with regard to sex, race, marital/partner status, residence at home, stroke risk factors, or estimated prestroke mRS. None of the patients in the wake-up group received tPA, while 80 (4.9%) of all non-wake-up strokes received tPA.
Baseline clinical characteristics of wake-up vs non-wake-up strokesa
compares the eligibility for thrombolysis, with time eliminated as an exclusion criterion, for the wake-up and non-wake-up strokes. The most common exclusion in both groups was a mild stroke, as more than half of the patients in each group had rNIHSS scores <5. The number with mild stroke was significantly higher in the non-wake-up strokes (p = 0.004). Extreme hypertension and coagulopathies were also common exclusions. In the wake-up group, 98 (35.9%, 95% CI 30.4–41.8) patients would have been eligible for thrombolysis, compared with 406 (25.0%, 95% CI 22.8–27.4) in the non-wake-up group (p < 0.01).
Exclusions for tPA if time were not a factora
With regard to short-term outcomes, there were no significant differences in the discharge mRS scores or 90-day mortality after adjusting for age, sex, race, prestroke mRS, rNIHSS, and prior atrial fibrillation between the wake-up and non-wake-up groups. Ninety-day mortality rates were 15.8% in the wake-up group and 15.6% in all others (p = 0.57). Median discharge mRS was 3 in both the wake-up group and all others (p = 0.94).
The previous analysis assumed that the 219 strokes with no estimate of stroke onset time were non-wake-up strokes. In order to evaluate the potential for misclassification, the data were reanalyzed with the assumption that the 219 were wake-up strokes. With this reclassification, the only change was that baseline rNIHSS was no longer significantly different between the 2 groups (median rNIHSS [IQR] was 4 [2, 8] for wake-up and 3 [2, 7] for non-wake-up, p = 0.70; the percentage with rNIHSS <5 was 57% for wake-up and 61% for non-wake-up, p = 0.20). Therefore, potential misclassification of strokes with unknown stroke onset times did not affect the conclusions drawn from this study.