(Stroke. 2000;31:1482.)
© 2000 American Heart Association, Inc.
Original Contributions |
From the Department of Psychiatry (M.K., R.G.R., J.T.K.), The University of Iowa College of Medicine, Iowa City, Iowa, and the Department of Neuropsychiatry (M.K.), Nippon Medical School, Tokyo, Japan.
Correspondence to Robert G. Robinson, MD, Department of Psychiatry, The University of Iowa, 200 Hawkins Dr, 2887 JPP, Iowa City, IA 52242-1057. E-mail robert-robinson{at}uiowa.edu
| Abstract |
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MethodsPatients with major (n=33) or minor (n=14) depression participated in a double-blind treatment study with nortriptyline or placebo. They were examined for change in depressive mood, measured by the Hamilton Rating Scale for Depression (HAM-D), and change in cognitive impairment, assessed by the Mini-Mental State Examination (MMSE), after treatment with nortriptyline or placebo. Cognitive treatment response, as measured by the MMSE, was compared between patients whose depression did and did not respond to treatment.
ResultsPatients whose poststroke depression remitted (predominantly associated with nortriptyline treatment) had significantly greater recovery in cognitive function over the course of the treatment study than patients whose mood disorder did not remit (predominantly associated with placebo treatment).
ConclusionsOur findings support the contention that poststroke major depression leads to a "dementia of depression." Prior studies failed to show an effect of treatment because the effect size was too small. Successful treatment of depression may constitute one of the major methods of promoting cognitive recovery in victims of stroke.
Key Words: cerebrovascular disorders cognitive disorders depression drug therapy
| Introduction |
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In spite of this general concurrence of findings, all prior double-blind treatment trials have failed to show an improvement in cognitive function among patients with poststroke depression who were given active antidepressant therapy.9 10 11 This finding led Andersen et al9 to suggest that the cognitive impairment may be the cause of depression. We subsequently refuted this hypothesis by demonstrating that among patients not treated for depression, there was a correspondence between depression and cognitive function. Depressed patients whose mood spontaneously improved over the first 3 months after stroke showed a significantly greater improvement in cognitive function than depressed patients whose mood did not improve, and similarly, depressed patients with spontaneous improvement in cognitive function showed an associated significant mood improvement.12 If poststroke cognitive impairment had caused depression, cognitive impairment would be expected to remain even if mood improved. We therefore sought to examine whether improvement in cognitive function is associated with successful treatment of poststroke depression. We combined data from our prior double-blind treatment studies of poststroke depression and compared patients whose depressive disorder did and did not respond to treatment.
| Subjects and Methods |
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Neurological Evaluation
Neurological evaluations for all patients were performed with
the standardized examination and rating criteria from the Stroke Data
Bank.20 All neurological evaluations and CT scan readings
were performed with the investigator blind to the findings on the
psychopathological examination. Lesion volume was calculated from the
ratio of the largest cross-sectional area of the lesion to the
cross-sectional area of the brain at the level of the body of the
lateral ventricle.5
Drug Protocol
The patients participating in the treatment study were given
nortriptyline or placebo in a single daily dose at bedtime. Patients
were randomly assigned to either active treatment or placebo. Both the
patients and examiners were unaware of which treatment was given. In
the first group (ie, Baltimore patients), patients were given 20 mg/d
for 1 week, 50 mg/d for 2 weeks, 70 mg/d for 1 week, and 100
mg/d for the last 2 weeks of the study. They were evaluated before
treatment began and at 2-week intervals during the 6-week treatment
period. Patients in the second group (ie, Iowa patients) were given 25
mg/d for 1 week, 50 mg/d for 2 weeks, 75 mg/d for 3 weeks, and 100 mg/d
for the last 6 weeks of the study. They were evaluated before treatment
began and at 3-week intervals during the 12-week treatment period. In
the present study, we analyzed the 2 groups by combining
their data according to the dosage of nortriptyline, ie, the
evaluations of weeks 0 (0 mg), 2 (50 mg), 4 (70 mg), and 6 (100 mg) in
the first group were considered approximately equivalent to those of
weeks 0 (0 mg), 3 (50 mg), 6 (75 mg), and 9 (100 mg) in the second
group, respectively.
Statistical Analysis
Parametric data were analyzed with t
tests (2-tailed), repeated-measures ANOVA, and ANCOVA. Descriptive
statistics calculated for these data were means and standard
deviations. In general, parametric data were used when the data
were normally distributed. Assessment of MMSE scores demonstrated a
normal distribution for both active-treatment and placebo-treated
patients at initial evaluation and at follow-up.
Nonparametric data were analyzed with
2 tests (with Fishers exact test, if sample
sizes were prohibitively small).
| Results |
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21=9.39,
P=0.0060). There were no significant differences in stroke
type, lesion location, and neurological deficits between the 2 groups
(Table 2
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Relationship of Treatment Response to the Change in Cognitive
Function
We next examined the relationship between the change in cognitive
function and treatment response. Patients were divided into responder
(n=24; major depression=15, minor depression=9) and nonresponder (n=23;
major depression=18, minor depression=5) groups based on the criteria
above. The responder group included 16 patients treated with
nortriptyline and 9 with placebo. The nonresponder group included 5
patients treated with nortriptyline and 18 with placebo. There were no
significant differences between the responder group (18.33±4.23) and
the treatment-failure group (17.00±3.87) in their baseline HAM-D
scores. There were no significant differences between the 2 groups in
demographic characteristics, stroke characteristics, or neurological
findings. We also examined the change in MMSE scores between groups.
Repeated-measures ANOVA of the MMSE scores demonstrated a significant
group-by-time interaction (F3,108=4.45,
P=0.0055) (ie, cognitive function in the responder group
recovered more quickly than in the treatment-failure group). Planned
comparisons revealed that the responders had significantly higher (less
impaired) MMSE scores than the nonresponders at nortriptyline doses of
75 mg/d (t41=-2.17, P=0.036)
and 100 mg/d (t40=-2.34,
P=0.024) (Table 4
). Although
some placebo patients (n=8) were in the responder group, there were
significantly more nortriptyline-treated patients in this group (n=16)
than in the nonresponder group (n=5)
(
21=7.90,
P=0.0032). In addition, there were no significant
differences in the number of patients treated for 12 weeks in the
responder (n=6) compared with the nonresponder (n=8) groups
(
21=0.53,
P>0.75). We also used intention-to-treat methods in
analyses that included the 12 patients who withdrew from the
study. Repeated-measures ANOVA of the MMSE scores continued to show a
significant group-by-time interaction
(F3,156=3.94, P=0.0097).
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Change of Each Individual Item in the MMSE
Cognitive domains examined by the MMSE include orientation,
registration, attention-calculation, recall, language, and visuomotor
integrity. There was significantly greater improvement in both
attention-calculation (t39=-2.15,
P=0.038) and recall (t39=-2.05,
P=0.047) items in the responders than in the nonresponders
(Figure 1
).
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Comparison Between Nortriptyline-Treated Patients and Placebo
Patients
If only nortriptyline-treated patients were used in the
treatment-response group compared with all placebo patients in the
treatment-failure group, there was still a significant group-by-time
interaction (F3,93=2.96, P=0.036),
which indicates that the failure to demonstrate cognitive improvement
in prior treatment trials was not the result of nortriptyline drug
effects such as sedation or impaired attention.
Among patients given nortriptyline, we compared responders (n=16) and nonresponders (n=5) using pretreatment MMSE scores as covariants. ANCOVA analyses of MMSE scores for patients responding to nortriptyline showed significantly greater improvement than the nortriptyline nonresponders at doses of 75 mg/d (F1,13=2.39, P=0.0034) and 100 mg/d (F1,13=21.79, P=0.0004). Among patients given placebo only (8 responders and 18 nonresponders), repeated-measures ANOVA also showed a significant group-by-time interaction (F3,57=3.17, P=0.031), with the responders showing more improvement in cognitive function than the nonresponders.
Comparison Between Major Depression and Minor Depression
Because our previous publications have identified that cognitive
impairment is associated with major but not minor depression, we wanted
to determine whether major and minor depression show the same
phenomenon of cognitive improvement with response to treatment. Among
patients with major depression, responders (n=15) showed significantly
greater improvement in cognitive function than nonresponders (n=18)
(repeated-measures ANOVA of MMSE scores showed a significant
group-by-time interaction; F3,69=4.19,
P=0.0087) (Figure 2
). Among
patients with minor depression (9 responders and 5 nonresponders),
repeated-measures ANOVA of MMSE scores showed no significant group
effect, time effect, or group-by-time interaction.
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| Discussion |
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Before further discussion of our results, it is important to acknowledge the methodological limitations of this study. First, our only measure of cognitive function was a brief, language-dominated examination, the MMSE. A more detailed neuropsychological battery would have documented whether cognitive improvement occurred in areas other than attention and recall and how many of these cognitive disorders met the diagnostic criteria for vascular dementia. Second, the combination of 2 patient groups that had different durations of treatment could have led to differential treatment response. We showed, however, that duration of treatment did not explain the improvement in cognitive function among the treatment responders. Third, the use of multiple comparisons could have led to type I errors identifying random findings as significant.
The most significant finding from this study was that for the first time, we showed in a double-blind, controlled treatment trial that patients with stroke had partially reversible cognitive dysfunction when their depressive disorder was successfully treated. Because the cognitive impairment involved more than 1 area of cognitive function (ie, memory and attention), it suggests that this disorder is probably a dementia of depression. This finding also supports our contention that poststroke depression produces a cognitive impairment5 6 but refutes the hypothesis posed by Andersen et al9 that the cognitive impairment produces the depression.
One might logically wonder why this improved cognitive function related to mood improvement was not noted in the prior treatment studies that documented improved mood with active treatment of poststroke depression. We believe the answer to this question is related to effect size. Nortriptyline treatment of depression, as demonstrated in the present study, produced a mean change of 12.1 points on the HAM-D, or a 69.5% decline, compared with a 36.8% (6.8 points) decline in the placebo group. The effect size was 0.71. When this effect size is compared with the effect of nortriptyline on MMSE (ie, 9.6% [1.8 points] for active treatment and 5.6% [1.3 points] for placebo treatment; effect size 0.16), it would take a group size of 598 to demonstrate a significant effect of nortriptyline on cognitive function with an 80% probability. By dividing patients on the basis of response to treatment, the effect on MMSE was 17.2% (3.0 points) for responders and only 1.3% (0.14 points) for nonresponders, for an effect size of 0.96. This allowed a significant difference to be detected with a group size of only 47.
The other major finding from the present study was that improved cognitive function was related to mood improvement and not to nortriptyline itself. Approximately one third of the patients responding to treatment were taking placebo and showed the same cognitive improvement as patients taking nortriptyline. This suggests that cognitive impairment was associated with the mechanism of depression and was not a parallel phenomenon of depression with a separate mechanism. In other words, nortriptyline could have affected 2 different neurophysiological mechanisms: one related to depression and one related to cognitive impairment. The fact that mood improvement with placebo was associated with the same cognitive improvement as nortriptyline suggests that the mechanism of depression, not the mechanism of nortriptyline, was responsible for the cognitive improvement. This lends further support to the hypothesis that poststroke major depression causes a dementia of depression.
Another interesting finding was that improved mood led to improvement in specific cognitive domains. It is known that the cognitive domains most likely to be defective after stroke are memory, orientation, language, and attention.21 On the other hand, patients with functional (ie, no known brain lesion) depression and dementia of depression have been shown to perform poorly on cognitive tasks involving memory and concentration.22 23 Thus, our findings are consistent with the cognitive deficits found in patients with functional depression and therefore provide additional validation that poststroke depression produces a dementia of depression.
Finally, our previous studies5 24 demonstrated that cognitive impairment was associated with major but not minor depression. We therefore did not expect to see any significant improvement in cognitive function among patients whose minor depression responded to treatment. This hypothesis was supported when we analyzed patients with minor depression separately. This finding is also consistent with our previous suggestion that minor depression has a different pathophysiological mechanism than poststroke major depression.25
In conclusion, this study has demonstrated that an impairment associated with stroke can be significantly improved by treatment of poststroke depression. This finding adds greater urgency to the need to identify and treat depression in patients who have suffered a stroke. Any treatment method that improves mood should improve cognitive function in patients with poststroke depression. Thus, treatment of depression may constitute one of the major methods of improving cognitive recovery in victims of stroke.
| Acknowledgments |
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Received February 22, 2000; revision received April 25, 2000; accepted April 25, 2000.
| References |
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