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(Stroke. 1999;30:2008-2012.)
© 1999 American Heart Association, Inc.
Original Contributions |
From the Department of Neurology, Bispebjerg Hospital, and Department of Neurology, Gentofte Hospital (T.S.O.), Copenhagen, Denmark.
| Abstract |
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MethodsWe included the 223 patients (19%) with the most severe
strokes (Scandinavian Stroke Scale score <15 points) from the 1197
unselected patients in the Copenhagen Stroke Study. Of these, 139
(62%) died in the hospital and were excluded. The 26 survivors (31%)
with a good functional outcome (Barthel Index
50 points) were
compared with the 58 survivors (69%) with a poor functional
outcome (Barthel Index <50 points). The predictive value of the
following factors was examined in a multivariate
logistic regression model: age; sex; a spouse; work; home care before
stroke; initial stroke severity; blood pressure, blood glucose, and
body temperature on admission; stroke subtype; neurological impairment
1 week after onset; diabetes; hypertension; atrial fibrillation;
ischemic heart disease; previous stroke; and other disabling
disease.
ResultsDecreasing age (odds ratio [OR], 0.50 per 10-year decrease; 95% CI, 0.25 to 0.99; P=0.04), a spouse (OR, 3.1; 95% CI, 1.1 to 8.8; P=0.03), decreasing body temperature on admission (OR, 1.8 per 1°C decrease; 95% CI, 1.1 to 3.1; P=0.01), and neurological recovery after 1 week (OR, 3.2 per 10-point increase in Scandinavian Stroke Scale score; 95% CI, 1.1 to 7.8; P=0.01) were all independent predictors of good functional outcome.
ConclusionsPatients with the most severe strokes who achieve a good functional outcome are generally characterized by younger age, the presence of a spouse at home, and early neurological recovery. Body temperature was a strong predictor of good functional outcome and the only potentially modifiable factor. We suggest that a randomized controlled trial be undertaken to evaluate whether active reduction of body temperature can improve the generally poor prognosis of patients with the most severe strokes.
Key Words: neuropsychological tests outcome prognosis stroke
| Introduction |
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This study evaluates the prognostic importance of various stroke characteristics and social, demographic, and medical factors in patients with the most severe strokes in the unselected population of the Copenhagen Stroke Study.
| Subjects and Methods |
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In this part of the Copenhagen Stroke Study we included patients with
only the most severe strokes1 : those who had a
Scandinavian Stroke Scale (SSS) score on acute admission <15 points
and who survived. Nine hundred seventy-four patients (81%) were
excluded because initial stroke severity was not very severe (SSS score
15 points on admission). One hundred thirty-nine (62%) of the
patients with a very severe stroke (SSS score <15 points on admission)
were excluded because they died in the hospital. The cutoff point of 15
points for the SSS score is arbitrary and was chosen because we have
previously shown that patients with an initial stroke severity <15
points generally have a poor prognosis and represent the most
severe strokes.1 Thus, a total of 84 patients (7%)
who survived a very severe stroke were included in the
analyses. These patients were stratified into 2 groups: (1)
those who eventually had a good functional outcome, ie, a Barthel Index
(BI) score of
50 points after completed rehabilitation, and (2) those
who had a poor functional outcome, ie, a BI score <50 points after
completed rehabilitation. A cutoff of 50 points for the BI score was
chosen arbitrarily to dichotomize the variable. This seems
justified since only 8% of the patients with a score
50 points
eventually had to be discharged to a nursing home facility compared
with 91% of the patients with a score of <50 points.
Stroke was defined according to the World Health Organization criteria as rapidly developed clinical signs of focal disturbance, lasting >24 hours or leading to death, with no apparent cause other than vascular origin. Subarachnoid hemorrhage was not included.5
The SSS was used to assess neurological impairment6 (Table 1
). The SSS evaluates level of
consciousness; eye movement; motor power in arm, hand, and leg;
orientation; aphasia; facial paresis; and gait on a total score from 0
to 58 (maximum). It was recorded on acute admission, the day after
admission, weekly during the hospital stay, and at discharge.
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The BI was used to assess functional disability.7 It evaluates basic activities of daily living, such as feeding, grooming, transfer, dressing, toileting, bathing, walking, incontinence of bowel and bladder, and stair walking, on a total score from 0 to 100 (independent functional level) points. The BI was assessed by the nursing and training staff during the first week, weekly throughout hospital stay, and at discharge after completed rehabilitation.
The following factors were considered in the analysis of
predictors of good outcome: age; sex; marital status; home help (ie, a
professional who helps with cleaning, shopping, etc); stroke severity
on admission (SSS); stroke subtype (hemorrhage/infarct); blood
pressure, blood glucose, and spontaneous body temperature on admission;
diabetes; atrial fibrillation; hypertension; ischemic heart
disease; previous stroke; previous transient ischemic attack;
daily alcohol consumption; and other disabling comorbidity. The
classification of specific factors was as follows: (1)
diabetespatients with known diabetes before stroke and patients with
diabetes diagnosed after stroke onset either during the hospital stay
or because admission plasma glucose was >11 mmol/L, in accordance
with the World Health Organization diagnostic criteria for
diabetes8 ; (2) atrial fibrillationif present on
admission ECG; (3) hypertensionon antihypertensive treatment at the
time of admission or hypertension diagnosed during the hospital stay by
repeated detection of blood pressure
160/95 mm Hg; (4)
ischemic heart diseasea history of ischemic heart
disease or ischemic heart disease diagnosed during the hospital
stay; (5) daily alcohol consumption1 drink per day (12 g alcohol) or
more on average; (6) comorbidityinformation concerning comorbidity
believed to interfere with the patient's ability to perform basic
activities of daily living was obtained on admission and included
disabling diseases other than previous stroke (eg, amputation, multiple
sclerosis, severe dementia, heart failure, latent or persistent
respiratory insufficiency); various comorbidities were not registered
separately, and the influence of specific comorbidities was therefore
not evaluated; (7) temperaturebody temperature on acute admission was
recorded with a Diatek model 9000 infrared aural thermometer
(Diatek); this device registers tympanic membrane temperature, which
correlates well with core body temperature9 ; and (8)
stroke subtypehemorrhage or ischemic infarction as
seen on CT scan.10
A priori we believed that young age, female sex, a spouse, no home help before stroke, less severe stroke, infarction as opposed to hemorrhage, high blood pressure, no elevated blood glucose, low spontaneous body temperature, no diabetes, no atrial fibrillation, hypertension, no ischemic heart disease, no previous stroke, previous transient ischemic attack, no daily alcohol consumption, and no other disabling comorbidity were all candidates to be potential predictors of good outcome.
Statistical analysis was done with the SPSS package for
Windows.11 Student's t test was used in
univariate analysis for continuous data and the
2 for noncontinuous data. To evaluate the
prognostic importance of multiple factors independently of other
factors, a multiple logistic regression model for poor versus good
outcome was created. Poor functional outcome was coded as 0, and good
functional outcome was given the value of 1. All variables of
interest were tested backward to fit the full model with all the
potential explanatory variables. Unimportant variables were
then removed one at a time until all those remaining in the model
contributed with probability value <0.2. The 2 methods of multiple
regression analysis, backward and forward regression, often
yield the same model, but differences are not uncommon. To select the
"best model," backward logistic regression including only
variables with a P value <0.2 was followed by a forward
logistic regression including the same variables. The 2 methods
yielded similar models. The explanatory power of the equation was
determined by the value of correct classification (the percentage of
patients correctly classified as achieving a poor or a good functional
outcome from the information given by the independent variables
included in the final model). The required 2-tailed significance level
for all tests was set at 0.05.
| Results |
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50 points after completed rehabilitation) was achieved by
26 (31%), and 58 patients (69%) had a poor functional outcome
(a final BI score <50 points).
Table 2
depicts comparisons of stroke
severity, length of hospital stay, and discharge placement between the
2 groups. Initial stroke severity (as measured by the SSS score on
admission) was quite similar between groups; in addition, the
frequencies of patients with decreased consciousness on admission
(evaluated by the SSS subscore for consciousness) were comparable. Only
8% of patients with a good functional outcome were discharged to a
nursing home after completed rehabilitation compared with 91% of the
patients with a poor functional outcome (Table 2
).
|
Table 3
shows a comparison of
potential predictors of good functional outcome between the 2 groups.
Patients with a good functional outcome were younger, more often
married, working, and had a higher frequency of daily alcohol
consumption and a lower frequency of other disabling comorbidity in the
univariate analyses. However, most of these
differences were explained by the difference in age between groups. The
multivariate logistic regression analysis of
factors obtainable on acute admission revealed 3 independent factors as
predictors of good outcome: age (odds ratio [OR], 0.50 per 10-year
decrease; 95% CI, 0.25 to 0.99; P=0.04), a spouse at home
(OR, 3.1; 95% CI, 1.1 to 8.8; P=0.03), and spontaneous body
temperature on admission (OR, 1.8 per 1°C decrease; 95% CI, 1.1 to
3.1; P=0.01) (Figure 1
). In
this model, correct classification was obtained in 75% of the
cases.
|
|
Figure 2
shows neurological impairment in
the 2 groups as a function of time from stroke onset. Neurological
impairment at the time of acute admission was identical in the 2
groups, but the day after admission a diversion in scores was evident,
reaching a significant level after 1 week (SSS score 1 week after
admission was 27.4 [SD 19.8] points in patients who eventually had a
good functional outcome compared with 13.3 [8.2] points in patients
who eventually had a poor functional outcome; P<0.001).
Adding neurological impairment at week 1 to the
multivariate logistic regression model of predictors of
good outcome increased the rate of correct classification to 85%.
Neurological impairment at week 1 was an independent predictor of good
outcome (OR, 3.2 per 10-point increase in SSS score; 95% CI, 1.3 to
7.8; P=0.01) (Figure 1
). The difference in
neurological impairment after 1 week was maintained throughout the
hospital stay.
|
Figure 3
depicts the level of disability
in the 2 groups as a function of time from stroke onset. There was a
marked difference in BI score 1 week after admission (28.6 points [SD
3.2] versus 3.2 points [SD 5.8]; P<0.001), and this
difference increased steadily throughout hospital stay to 79.2 points
(17.3) versus 10.2 (13.5) after completed rehabilitation
(P<0.001).
|
| Discussion |
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Prognostic factors found exclusively in patients with the most severe strokes have not been examined before. We found 4 factors related to a good functional outcome in this group: decreasing age, a spouse at home, spontaneous body temperature on admission, and early neurological recovery. A correct classification was achieved in 85% of the cases in the logistic regression prediction model with these 4 factors: age, presence of a spouse at home, body temperature, and SSS score after 1 week. A 10-year decrease in age corresponded to a 50% reduction in the relative risk of a poor outcome. That functional outcome decreases with increasing age is in agreement with previous findings in the general stroke population.13 14 This relation is most likely due to an age-linked reduced ability for functional compensation15 and is not to any greater extent due to a relation between increasing age and comorbidity since these parameters were not highly correlated (Spearman correlation coefficient, 0.11). The existence of a spouse at home increased the relative chance of a good outcome 3-fold, independent of age, sex, stroke severity, and other factors. This is probably a reflection of the importance of a good social network to outcome in general.16 17
We have previously reported a relation between spontaneous body temperature and mortality/neurological impairment in survivors.12 18 That a good functional outcome is so strongly related to body temperature, as reported here, is nevertheless surprising: a 1°C decrease in body temperature corresponded to an almost doubled relative chance of a good functional outcome, independent of other factors. This finding may suggest that lowering body temperature could point to a treatment effect, provided that the relation is causal.
Degree of neurological impairment 1 week after stroke onset added substantial information regarding whether or not a good functional outcome could eventually be achieved. Initial neurological impairment was identical in patients with good and poor functional outcome, but neurological recovery within the first week markedly differed between groups, and this difference explained most of the difference in both neurological and functional outcome after completed rehabilitation. This suggests that early neurological recovery is the basis for good functional outcome in patients with the most severe strokes. Early spontaneous reperfusion of the ischemic penumbra surrounding the core area of infarction could in part be the pathophysiological background for early neurological recovery.19 20
Other comorbidity such as diabetes, hypertension, ischemic heart disease, and other disabling disease did not predict functional outcome, nor did the type of stroke. This confirms previous findings in the general stroke population.3 10 21 22 23 24 It should be emphasized that function was defined by the ability to perform basic activities of daily living as measured by the BI. An influence on the ability to perform instrumental activities of daily living or higher cognitive functions can therefore not be excluded. We have previously reported low acute systolic blood pressure to predict poor outcome in the subgroup of patients with early stroke in progression.25 In the present study of unselected patients with the most severe strokes, blood pressure did not predict functional outcome. Blood pressure seems important to the development of early stroke in progression, but not to the prognosis of the stroke population as a whole.
Body temperature is a strong predictor of functional outcome in patients who survive the most severe strokes. It was also the only potentially modifiable outcome predictor. We suggest that a randomized controlled trial be performed to evaluate whether active reduction of body temperature can improve the generally poor prognosis of the patients with the most severe strokes.
| Acknowledgments |
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| Footnotes |
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Received March 26, 1999; revision received May 17, 1999; accepted June 4, 1999.
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