Citation:
Saxena, S K. (2006).
Prevalence and Correlates of Cognitive Impairment in Stroke Patients in
a
Rehabilitation Setting.
International Journal
of Psychosocial
Rehabilitation. 10 (2) 37-47.
Corresponding
Address:
Dr Sanjiv K Saxena
National University of Singapore,
E-mail: sanjiv@alumni.nus.edu.sg
Ph: (65) 91018190
Acknowledgement
:
This study was conducted as an MSc thesis
project in the Medical Faculty Graduate Studies Programme at National
University of Singapore
. I am thankful
to my Thesis Supervisors,
A/Prof Ng Tze Pin and Dr Fong and also to the staff of Ang Mo Kio
Community Hospital
and St Luke’s Hospital for their help and support in this study
Abstract:
Background: Stroke is associated with considerable physical and
psychological
impairment. Cognitive impairment in stroke patients is associated with
adverse
outcomes during their rehabilitative process.
Identifying the baseline factors associated with cognitive
impairment in
stroke patients would help the multidisciplinary team involved in the
rehabilitative process to maximize the functional recovery of stroke
patients.
Aim:
The aim of the study
was to ascertain the prevalence of cognitive impairment and its
baseline
determinants in the rehabilitation settings.
Methodology: A cross- sectional study of 200 stroke patients was
conducted in
two community (rehabilitation) hospitals. Assessments were made on
admission to
the hospitals which besides including information on sociodemographic,
clinical
and neurological variables also included assessment of functional and
neurological
impairment, depression and cognitive impairment.
Validated tools of assessment were used in
the study, viz. NIHS for neurological impairment, Barthel Index for
functional
assessment. AMT for cognitive impairment and GDS for depression.
Results: On admission 54.5 % of the patients were with cognitive
impairment.
In multivariate analyses, the independent significant predictors of
cognitive
impairment were age more than 81 years (OR=6.78, 95% C.I. 2.34, 19.64),
lesser
education (OR=4.73, 95% C.I. 1.41, 13.11), severe neurological
impairment on
admission (OR=5.00, 95% C.I. 1.70, 14.67) and depression on admission
(OR=3.19,
95% C.I. 1.61, 6.30).
Conclusion: Considerable proportion of stroke patients
present with cognitive
impairment during their rehabilitation which in turn is significantly
determined by modifiable baseline factors like depression. Judicious
identification of this group of patients would maximize the recovery of
stroke
patients.
Introduction
Stroke is a
disease with considerabe physical 1,2 and psychosocial
impairments. 3-7
Dementia and
cognitive impairment are such psychological impairments in stroke
patients
which besides having as high a prevalence of and 17-38% 3-7
respectively are also associated with many short and long term poorer
outcomes
including poorer functional recovery in stroke patients. 8-10
Adopting clinical diagnostic criteria like DSM-1V
for dementia may
miss out the cases among the stroke patients who are cognitively
impaired but
not demented known as “cognitive impairment, no dementia” (CIND), 11
which besides being an important challenge in dementia epidemiology
also has
consistently been reported as a
correlate of poorer functional recovery in stroke patients.8-10
Low et al 11 in their
cross-sectional
survey observed that 33.3% were cognitively impaired but not demented
(CIND)
2.4% had possible dementia and 64.3% of the subjects were cognitively
normal.
Though the prevalence of cognitive impairment in
stroke patients is
high and is associated with adverse effects on the rehabilitative
outcomes
still there is a lack of consensual agreement regarding determinants
of cognitive impairment e.g.
increasing age was found to be a
significant correlate of post
stroke cognitive impairment by Allan et al. 12 but T.K.
Tatemichi 13
did not find increasing age to be
significantly associated with post
stroke cognitive impairment. Likewise R.M. Parekh et al 14
did not find significant relationship between depression and cognitive
impairment but R.G. Robinson et al 15 found a significant
relationship between cognitive deficits and depression in stroke
patients.
Knowledge about such baseline modifiable and
non-modifiable
determinants of cognitive impairment in stroke patients would help the
multidisciplinary team involved in the rehabilitative process of stroke
patients to adopt an appropriate treatment modality to reduce the
burden of
cognitively impaired stroke patients which in turn will help maximize
the
functional recovery of stroke patients during their rehabilitation.
The aim of the study was to ascertain the prevalence
and baseline
determinants of cognitive impairment in stroke patients.
Methods and Materials
Methods
Patients
A cross-sectional study
was conducted on 252 stroke patients who were consecutively admitted
into two
rehabilitation hospitals in Singapore
during the period from April 2002 to September 2002. The patients
satisfied the
WHO criteria for defining stroke (defined as a condition characterised
by
rapidly developed clinical signs of focal disturbance of cerebral
function
lasting more than 24 hours with no apparent cause other than vascular
origin). All
the patients in the study gave informed consent for participation in
the study.
We excluded 48 patients with severe dysphasia because the measurement
tools
used in the study required participants to be able to communicate.
Another four
patients refused participation, hence 200 patients fulfilled the
inclusion
criteria for enrolment into the study.
Measurements
Information obtained on
admission for 200 patients included socio-demographic
variables (age, gender, ethnicity, marital status, education
level, living
arrangement , presence of caregiver). Clinical
variables extracted from clinical case records included presence of
cardiovascular
risk factors, viz. smoking, hypertension, hyperlipidaemia, diabetes,
ischemic
heart disease and atrial fibrillation, visual impairment and hearing
impairment. Neurological variables
included stroke lesion type (ischemic vs haemorrhagic), location of
stroke
(cortical versus non-cortical), side (left or right sided) and
distribution
(unifocal or multi-focal) based on CT head reports, and
whether the stroke was recurrent. Post-stroke urinary
incontinence
(defined as involuntary loss of urine in a post-stroke patient),
dysphagia (as
diagnosed by a swallowing therapist), aspiration pneumonia (as
diagnosed by a
clinician) and post-stroke seizures (excluding those with pre-existing
epilepsy), on-admission Ryle’s tube and urinary catheterization.
On admission the patients were assessed on
neurological, depressive
symtoms, cognitive status, and physical functioning using the National
Institute of Health Stroke Scale (NIHSS), Geriatric Depression Scale
(GDS-15), Abbreviated
Mental Test (AMT) and Barthel Index (BI).
Neurological and
functional assessment was performed by a physician (SKS) and
questionnaire
interviews were performed by a trained research nurse, with
translations for
non-English speaking patients.
NIHSS:
Assesses level of consciousness, horizontal gaze, visual fields,
facial palsy, motor strength, ataxia, sensory system, language,
dysarthria and
extinction or inattention. The scale scores range from 0 to 42, with 42
denoting
the most severe neurological impairment. The NIHSS has been shown to
have high
intra and inter-rater reliability 16,
and predict long-term stroke outcome17,
and
post-acute care disposition among stroke patients18. Three categories of neurological impairment,
namely mild, moderate and severe, were defined with the following
cut-off values:
mild impairment = 1-6, moderate impairment = 7-12 and severe impairment
= 13-42.
GDS: The 15-item short form version of
the Geriatric Depression Scale (GDS-15) was used to assess depressive
symptoms.
The short-GDS has been found to be a suitable instrument to screen for
depression in the general population 19
and validated for use in the elderly Chinese population locally20.
It has scores ranging from 0 to15, with a
score of 5 to 10 indicating mild depression and a score of 11 to 15
indicating
severe depression.
Abbreviated
Mental Test (AMT) : was used
to assess cognitive impairment. In
elderly patients, AMT has been shown to give good predictive validity
of
cognitive impairment and dementia21 and has been validated
in local
settings by Sahadevan et al.22 The
10-item scale gives scores ranging from 0 to10 with a score of 7 or
less
indicating cognitive impairment.
Barthel Index: Physical
functioning and
disability was assessed by the Barthel Index (BI) 23 for
independence in activities of daily living (grooming, transfer,
walking,
bladder and bowel control, dressing, climbing stairs, feeding and
bathing)
which has been validated and is widely used in stroke patients24.
The scores of the scale range from 0 to 100, with a score of 100
denoting
complete independence. Three ordinal
categories
of functional disability were defined using the following cut-off
values: (1)
severe: 0-50; (2) moderate: 51-75; (3) mild to no impairment: 76-100. ADL dependence upon admission, upon planned
discaharge and at six months after stroke onset was defined as Barthel
Index
score ≤ 50.
Statistical Analysis:
Besides ascertaining the prevalence, the baseline
factors predicting
post stroke cognitive impairment were ascertained and modeled using
Logistic
Regression analyses. Significant baseline variables identified from
univariate
analyses were included in the final regression model using forward
selection
procedures for entry at p=0.05 and removal at p=0.10. The strengths of
association of the predictors were expressed as the odds ratios and
their 95%
confidence intervals.
Results:
Patient characterstics
The patients in the study were aged between 40 and
96, mean 71.5
(S.D. = 10.5); 54% were males; 88% were Chinese, 7% Malays, and 5%
Indians; 50%
were married, 7% were unmarried and 43% were either widowed or
divorced. Among
them, 10% were living alone, 12.5% did not have an identifiable care
giver.
Visual and hearing impairment were present in 10%
and 5% of the
patients. The prevalence of cardiovascular risk factors and
co-morbidities
were: hypertension: 87%; diabetes: 47%; smokers: 45%; ischemic heart
disease:
22%; atrial fibrillation: 7%; hyperlipidaemia: 72%. The stroke lesions
were
hemorrhagic in 12.5% of the patients, and cortical in 28%; 47% had left
sided
lesion; multifocal 49%; 42% had recurrent stroke. Among
the patients, 25% had post-stroke
dysphagia, 59% urinary incontinence, 5% aspiration pneumonia; 2%
epilepsy.
Neurological impairment was assessed according to the NIH scale as mild
in 47%
of the patients, moderate in 36% and severe in 16% of the patients. On
admission,
60% of the patients were with depressive symptoms and 54% were
cognitively
impaired.
Prevalence of cognitive impairment:
On
admission 109/200 (54.5%) of the patients were cognitively
impaired.
Univariate
analysis of
factors associated with cognitive impairment on admission
On univariate logistic
regression the factors significantly associated with cognitive
impairment on
admission were (Ref. Table 1): Socio-Demographic
variables:
(a) Age: 66-80
years (O.R.-2.03, 95%C.I.-1.06,
3.81);
< = 81 years (O.R.-6.09
95%C.I.-2.42, 15.42); (b) Gender:
Females (O.R.-1.83, 95%C.I.-1.04,
3.23)
(c) Marital
Status: Widow/er, Divorced/ee: (O.R.-1.88,
95%C.I.-1.04, 3.32).
(d) Educational
Level: < = secondary level
(O.R.-4.52, 95%C.I.-1.91, 10.66)
Clinical Variable: (a) Depression (O.R.-4.23,
95%C.I.-2.31, 7.73). (b) Severe functional
impairment: Severe (O.R.15.72, 95%C.I.-1.89, 130.44)
Neurological variable: (a) Moderate
Neurological impairment (O.R.-2.96, 95%C.I.-1.57,
5.58) (b)
Severe Neurological
impairment (O.R.-7.10, 95%C.I.-2.66,
18.91)
(c) On admission
Ryle`s tube: (O.R.-5.81, 95%C.I.-1.93, 17.51) (d) Urinary incontinence: (O.R.-3.51, 95%C.I.-1.94, 6.33) (e) Post
stroke aspiration pneumonia: (O.R.-8.06,
95%C.I.-1.002, 64.66)
Table 1: Univariate
Analysis of the factors associated with cognitive impairment on
admission:
| Socio Demographic Variables |
Cognitively Impaired
No:
109(54.5%)
|
Normal Cognition
No:
91(45.5%) |
p |
O.R. |
95%C.I. |
| Age: |
>
= 65 yrs. |
24
(22.0) |
39
(42.8) |
|
1.00 |
|
|
|
66-80
yrs. |
55
(50.4) |
44
(48.3) |
<0.05 |
2.03
|
1.06,3.81
|
|
<
= 81 yrs.
|
30
(27.5) |
8 ( 8.7) |
<0.01 |
6.09
|
2.42,15.42
|
| Gender: |
Male |
52
(47.7) |
57
(62.6) |
|
1.00 |
|
|
Female
|
57
(52.2) |
34
(37.3) |
<0.05 |
1.83
|
1.04,
3.24 |
| Ethnicity: |
Chinese: |
95
(87.1) |
82
(90.1) |
|
1.00 |
|
|
|
Malay
|
9 (8.2) |
5 (5.4) |
NS
|
1.55
|
0.50,
4.8 |
|
Indian
|
5 (4.5) |
4 (4.3) |
NS
|
1.07
|
0.28,
4.1 |
| Marital Status: |
Married:
|
49
(44.9) |
52
(57.1) |
|
1.00 |
|
|
|
Unmarried
|
5 (4.5) |
8 (8.7) |
NS
|
0.66
|
0.20,
2.1 |
|
Widow/Divorced
|
55
(50.4) |
31
(34.0) |
<0.05 |
1.88
|
1.04,
3.3 |
| Educational Level: |
>
Secondary: |
8
(7.3) |
24
(26.3) |
|
1.00 |
|
|
<
= Secondary
|
101(92.6)
|
67
(73.6) |
<0.01 |
4.52
|
1.91,10.66
|
| Living Arrangement:
|
Living
with
someone:
|
101 (92.6)
|
79 (86.8)
|
|
1.00
|
|
|
Living
Alone
|
8 (7.3) |
12
(13.1) |
NS
|
0.52
|
0.20,
1.33 |
| Care Giver: |
Present:
|
99
(90.8) |
76
(83.5) |
|
1.00 |
|
|
|
Absent:
|
10
(9.1) |
15
(16.4) |
NS
|
0.51
|
0.21,
1.20 |
| Clinical Variables |
|
|
|
|
|
| Visual Impairment: |
Present:
|
12
(11.0) |
8 (8.7) |
NS
|
1.28
|
0.50,3.29
|
|
Absent:
|
97
(88.9) |
83
(91.2) |
|
1.00 |
|
| Hearing Impairment: |
Present: |
4
(36.6) |
6 (6.5) |
NS
|
0.54
|
0.14,
1.97 |
|
Absent:
|
105
(96.3) |
85
(93.4) |
|
1.00 |
|
| Hypertension: |
Present |
97
(88.9) |
78
(85.7) |
NS
|
1.34
|
0.58,
3.11 |
|
Absent:
|
12
(11.0) |
13
(14.2) |
|
1.00 |
|
| Diabetes Mellitus: |
Present |
54
(49.5) |
40
(43.9) |
NS
|
1.25
|
0.71,
2.18 |
|
Absent:
|
55
(50.4) |
51
(56.0)
|
|
1.00 |
|
| Smoking: |
Present |
49
(44.9) |
42
(46.1) |
NS
|
0.95
|
0.54,
1.66 |
|
|
Absent:
|
60
(55.0) |
49
(53.8) |
|
1.00 |
|
| Ischemic Heart Disease: |
Present
|
30
(27.5) |
15
(16.4) |
NS
|
1.92
|
0.96,
3.85 |
|
Absent:
|
79
(72.4) |
76
(83.5) |
|
1.00 |
|
| Atrial Fibrillation:
|
Present |
10
(9.1) |
4 (4.3) |
NS
|
2.19
|
0.66
,7.25 |
|
Absent:
|
99
(90.8) |
87
(95.6) |
|
1.00 |
|
| Hyperlipidaemia: |
Present |
78
(71.5) |
66
(72.5) |
NS
|
0.95
|
0.51,
1.77 |
|
Absent:
|
31
(28.4) |
25
(27.4) |
|
1.00 |
|
| Depression: |
Present: |
82
(75.2) |
38
(41.7) |
<0.01 |
4.23
|
2.31,
7.73 |
|
|
Absent:
|
27
(24.7)
|
53
(58.2) |
|
1.00 |
|
| Functional Impairment:
|
Mild:
|
1
(0.9) |
8
(8.7) |
|
1.00 |
|
|
|
Moderate
|
37
(33.9) |
47
(51.6) |
NS
|
6.28
|
0.75,
52.37 |
|
Severe:
|
71
(65.1) |
36
(39.5) |
<0.05 |
15.7
|
1.89
,130.44 |
| Neurological Variables |
|
|
|
|
|
| Lesion Type: |
Hemorrhage |
12
(9.1) |
13
(14.2) |
|
1.00 |
|
|
Infarction:
|
97
(88.9) |
78
(85.7) |
NS
|
1.34
|
0.58,
3.11 |
| Lesion Location: |
Cortical:
|
37
(33.9) |
20
(21.9) |
|
1.00 |
|
|
Non
Cortical
|
66
(60.5) |
61
(67.0) |
NS
|
0.58
|
0.30,
1.11 |
| Lesion Distribution: |
Focal:
|
49
(44.9) |
36
(39.5) |
|
1.00 |
|
|
Multifocal:
|
53
(48.6) |
46
(50.5) |
NS
|
0.84
|
0.47,
1.51 |
| Recurrent CVA: |
Yes: |
18
(16.5) |
18
(19.7) |
NS
|
0.79
|
0.38,
1.64 |
|
No:
|
89
(81.6) |
71
(78.0) |
|
1.00 |
|
| Neurological Impairment: |
Mild:
|
36
(33.1) |
59
(64.8) |
|
1.00 |
|
|
|
Mod.:
|
47
(43.1) |
26
(28.5) |
<0.01 |
2.96
|
1.57,
5.58 |
|
|
Severe:
|
26
(23.8) |
6 (6.5) |
<0.01 |
7.10
|
2.66,
18.91 |
| On Adm. Ryle`s Tube: |
Present: |
23
(21.1) |
4
(4.3) |
<0.01 |
5.81
|
1.93,
17.51 |
|
|
Absent:
|
86
( 78.8) |
87
(95.6) |
|
1.00 |
|
| Dysphagia: |
Present |
32
(29.3) |
18
(19.7) |
NS
|
1.68
|
0.87,
3.26 |
|
Absent:
|
77
(70.6) |
73
(80.2) |
|
1.00 |
|
Urinary Incontinence:
|
Present: |
79 (72.4)
|
39 (42.8)
|
<0.01
|
3.51
|
1.94, 6.33
|
|
Absent:
|
39
(35.7) |
52
(57.1) |
|
1.00 |
|
| Aspiration Pneumonia: |
Present:
|
9
(8.2) |
1
(1.0) |
<0.05 |
8.06
|
1.00,
64.6 |
|
Absent:
|
100
(91.7) |
90
(98.9) |
|
1.00 |
|
| Epilepsy: |
Present: |
1 (0.9) |
3
(3.2) |
NS
|
0.27
|
0.02,
2.66 |
|
|
Absent:
|
108
(99.0) |
88
(96.7) |
|
1.00 |
|
Multivariate analysis of
the factors associated cognitive Impairment
in stroke patients on admission: (Ref.
Table 2)
The significant
predictors were: (a) Age more than 81 years (O.R. - 6.78,
C.I. - 2.34,
19.64) (b) Education
less than equal to secondary level (O.R.-4.73, C.I. - 1.41, 13.11)
(c)Severe
neurological impairment (O.R.-5.00, C.I. - 1.70, 14.67) (d) Depression (O.R.-3.19; C.I.-1.61, 6.30)
Table 2: Multiple forward
logistic regression of
cognitive impairment on admission in stroke patients*
| Variables |
Beta |
p |
O.R. |
95% C.I. |
Age:
|
> = 81 years
|
1.91
|
<0.01
|
6.78
|
2.34, 19.64
|
Education:
|
Less than
equal to Sec. Level
|
1.55
|
<0.01
|
4.73
|
1.41 , 13.11
|
Neurological
Impairment:
|
Severe
|
1.61
|
<0.01
|
5.00
|
1.70, 14.67
|
| Depression: |
Present:
|
1.16
|
<0.01
|
3.19
|
1.61, 6.30 |
* at probability of entry at 0 .05 and removal at 0.10
Discussion
In this study we have been able to identify the
group of stroke
patients who upon their admission to rehabilitation settings are
cognitively
impaired and their baseline correlates. This group of patients is
likely to
make lesser functional recovery.
One of the main aims of the study was to ascertain
the significant
determinants of cognitive impairment in stroke patients.
We observed that increasing age, lesser education,
severe
neurological impairment and depression were significant determinants of
cognitive impairment in stroke patients.
Severe stroke at onset has been consistently
reported to be a significant
correlate of post stroke cognitive impairment. 25, 26 This
suggests
that stroke induced brain injury affects cognition as well. However the
domains
of neurological impairment affecting the cognition in stroke patients
should be
identified so that more concerted efforts can be mounted for better
recovery
from neurological and cognitive impairment.
Likewise consistent with previous observations we
found increasing
age and lower educational level 13, 27 to be significant
correlates
of post stroke cognitive impairment. The probable reasons for this
could be
because with the increasing age there may be a concomitant degenerative
process
setting in and the lower educational level may be associated with
lesser mental
reserve.
In our study we found
depression to be a significant correlate of cognitive impairment. Till
to date
the intricate relationship between cognitive impairment and depression
remains
largely unclear. Hence an independent long-term longitudinal study to
evaluate a
temporal relationship between the two would help understand the topic
better as
more concerted efforts may then be applied to identify and treat the
entity
which is causative of the other outcome.
Lack of association between
functional disability and post stroke cognitive impairment has also
been
reported previously28 which suggests that post stroke
cognitive
impairment is mainly the result of stroke induced neurological injury.
Post stroke ryles tube insertion and urinary
incontinence were a
significant correlates of cognitive impairment in univariate analysis
but given
the presence of barthel index scale, were not independent correlates as
each of
these domains are measured separately on the barthel index scale.
Likewise vascular
risk factors were not a significant correlate of post stroke cognitive
impairment in our study as has also been reported previously. 29
In conclusion considerable
proportion of stroke patients present with cognitive impairment in the
rehabilitation settings and that cognitive impairment in stroke
patients is
determined by modifiable factors like depression. Hence by judiciously
identifying this group of patient the functional recovery of stroke
patients
can be maximized.
References
1. Mathers
C.D., Vos ET, Stevenson CE, Begg SJ. The Australian burden of
disease study: measuring the loss of health from diseases, injuries and
risk
factors. Med J Aust. 2000
Jun 19;172(12):592-6.
2. Scholte op Reimer
WJ, de Haan RJ,
Rijnders PT, Limburg M, van den Bos GA. The burden of caregiving in partners of
long-term stroke survivors. Stroke. 1998 Aug; 29(8):
1605-11.
3 Barba R,
Martinez S, Rodriguez E, Pondal M,
Vivancos J, Del Ser T. Post stroke dementia. Stroke 2000; 31: 1494-
1501.
4. Inzitari D,
Di Carlo A, Pracucci G, Lamassa
M, Paolivanni, Romenelli M, Spolveri S, Adriani P, Meucci I, Landini G,
Ghe