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The aim of this study was to analyze the efficacy of a cognitive training program on cognitive performance and quality of life in nondemented Parkinson's disease patients. Participants who met UK Brain Bank diagnosis criteria for Parkinson's disease, with I-III Hoehn & Yahr, aged 50-80, and nondemented (Mini-Mental State Examination ≥ 23) were recruited. Patient's cognitive performance and functional and quality-of-life measures were assessed with standardized neuropsychological tests and scales at baseline and after 4 weeks. Subjects were randomly and blindly allocated by age and premorbid intelligence (Vocabulary, Wechsler Adult Intelligence Scale-III) into 2 groups: an experimental group and a control group. The experimental group received 4 weeks of 3 weekly 45-minute sessions using multimedia software and paper-and-pencil cognitive exercises, and the control group received speech therapy. A total of 28 patients were analyzed. Compared with the control group participants (n = 12), the experimental group participants (n = 16) demonstrated improved performance in tests of attention, information processing speed, memory, visuospatial and visuoconstructive abilities, semantic verbal fluency, and executive functions. There were no observable benefits in self-reported quality of life or cognitive difficulties in activities of daily living. We concluded that intensive cognitive training may be a useful tool in the management of cognitive functions in Parkinson's disease. © 2011 Movement Disorder Society.
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Blind Randomized Controlled Study of the Efficacy of Cognitive
Training in Parkinson’s Disease
Anna Prats Parı
´s, MS, PhDc,
1,2
Heidi Guerra Saleta, PhDc,
3
Maria de la Cruz Crespo Maraver, PhDc,
1,4
Emmanuel Silvestre, PhD,
5
Maite Garolera Freixa, PhD,
6
Cristina Petit Torrellas, BA,
1
Silvia Alonso Pont, BA,
1
Marc Fabra Nadal, MS,
1
Sheila Alcaine Garcia, BA,
1
Maria Victoria Perea Bartolome
´, MD,
3
Valentina Ladera Ferna
´ndez, PhD,
3
and A
`ngels Baye
´s Rusin
˜ol, MD, PhD
1
*
1
Unitat de Parkinson i Trastorns del Moviment, Centro Me
´dico Teknon. Barcelona, Spain
2
Universidad Auto
`noma de Barcelona, Dpto. Biologı
´a Celular, Fisiologı
´a e Inmunologı
´a, Instituto de Neurociencias (INc), Barcelona, Spain
3
Universidad de Salamanca, Facultad de Psicologı
´a, Dpto. Psicologı
´a Ba
´sica, Psicobiologı
´a y Metodologı
´a. Salamanca, Spain
4
Divisio
´de Salut Mental, Fundacio
´Althaia, Manresa, Spain
5
Silvestre Hispanic Market Research & Services, Rocky Hill, Connecticut, USA
6
Consorci Sanitari de Terrasa Hospital, Terrasa, Spain
ABSTRACT: The aim of this study was to analyze
the efficacy of a cognitive training program on cognitive
performance and quality of life in nondemented Parkin-
son’s disease patients. Participants who met UK Brain
Bank diagnosis criteria for Parkinson’s disease, with I–III
Hoehn & Yahr, aged 50–80, and nondemented (Mini-Men-
tal State Examination !23) were recruited. Patient’s cog-
nitive performance and functional and quality-of-life
measures were assessed with standardized neuropsycho-
logical tests and scales at baseline and after 4 weeks.
Subjects were randomly and blindly allocated by age and
premorbid intelligence (Vocabulary, Wechsler Adult Intelli-
gence Scale-III) into 2 groups: an experimental group and
acontrolgroup.Theexperimentalgroupreceived4
weeks of 3 weekly 45-minute sessions using multimedia
software and paper-and-pencil cognitive exercises, and
the control group received speech therapy. A total of 28
patients were analyzed. Compared with the control group
participants (n 512), the experimental group participants
(n 516) demonstrated improved performance in tests of
attention, information processing speed, memory, visuo-
spatial and visuoconstructive abilities, semantic verbal flu-
ency, and executive functions. There were no observable
benefits in self-reported quality of life or cognitive difficul-
ties in activities of daily living. We concluded that intensive
cognitive training may be a useful tool in the management
of cognitive functions inParkinsonsdisease.V
C2011
Movement Disorder Society
Key Words: Parkinson’s disease; cognition; cognitive
training neuropsychology; cognitive impairment
Cognitive impairment is now recognized as a com-
mon feature of Parkinson’s disease (PD).
1
The preva-
lence of dementia in PD is close to 30% and is 6
times higher than that in the general population.
2
In
addition, approximately 19%–53% of nondemented
PD patients suffer from mild cognitive impairment
(MCI).
3–5
Cognitive impairment in PD is characterized by defi-
cits in executive functions, attention/working memory,
speed of information processing, visuospatial abilities,
and memory
6
and has important clinical consequences
for patient management. MCI and dementia in
PD have been linked to difficulties in activities of
daily living (ADLs).
7,8
Dementia has also been associ-
ated with rapid motor and functional decline,
9,10
increased mortality,
11,12
caregiver stress,
13
and risk of
institutionalization.
14
Because of the strong impact of cognitive disorders
on the quality of life (QOL) of patients and their
caregivers, it is important to find the necessary tools
to manage cognitive decline. Complementary to
------------------------------------------------------------
Anna Prats Parı
´s and Heidi Guerra Saleta contributed equally to this
work.
*Correspondence to: A
`ngels Baye
´s Rusin
˜ol, Unidad de Parkinson y
Trastornos del Movimiento, Centro Me
´dico Teknon, Pso. Bonanova 26,
Barcelona, Spain. 08022; 11741abr@comb.es
Relevant conflicts of interest/financial disclosures: Nothing to report.
Full financial disclosures and author roles may be found in the online
version of this article.
Received: 22 June 2010; Revised: 25 January 2011; Accepted: 28
January 2011
Published online 25 March 2011 in Wiley Online Library
(wileyonlinelibrary.com). DOI: 10.1002/mds.23688
RESEARCH ARTICLE
Movement Disorders, Vol. 26, No. 7, 2011 1251
pharmacological treatment, cognitive intervention pro-
grams have been shown to be useful in various patho-
logical conditions such as traumatic brain injury,
15
schizophrenia,
16–18
Alzheimer’s disease and demen-
tia,
19
and, more recently, MCI.
20,21
To our knowledge, only 2 studies have assessed the
effects of cognitive training (CT) in PD. Results of
both studies showed that this therapy had a positive
effect on the evolution of cognitive impairment.
22,23
The first study on CT in PD patients (Sinforiani
et al
22
) included a sample of 20 early-stage nonde-
mented PD patients with mild cognitive deficits who
underwent a 6-week rehabilitation program (12 one-
hour sessions), received CT (performed by neuropsy-
chological training software TNP), and motor rehabili-
tation. This descriptive study with no control group
showed a significant improvement in cognitive meas-
ures at the end of the training and after 6 months.
Sammer and colleagues
23
randomized (controlled
but not blind) 26 idiopathic PD patients. Twelve sub-
jects participated in a CT regimen (10- to 30-minute
sessions) that consisted of working memory tasks
requiring executive functions. Fourteen patients
received standard treatment, which included occupa-
tional therapy, physiotherapy, and physical treatment.
The outcome showed improved performance of the
group with cognitive treatment in 2 executive tasks,
whereas no improvement was seen in the standard-
treatment group.
We aimed to overcome previous methodological
limitations, conducting a blind, controlled study on a
homogeneous group of nondemented PD patients. We
performed an intensive CT program
24,25
(three 45-mi-
nute sessions per week for 4 weeks) to achieve more
clinical and cost-effective results.
20
An extensive and
detailed neuropsychological assessment, including mood,
QOL, and functional measures commonly used in PD,
was obtained at baseline and at the end of training.
The main objective of the present study was to
determine the efficacy of a CT program in a 4-week
randomized, controlled study of cognitive performance
and QOL in nondemented PD patients.
Patients and Methods
Subjects
This study recruited 46 patients from 2 centers in
Barcelona province: the Unit of Parkinson and Move-
ment Disorders from the Centro Me
´dico Teknon and
the Parkinson’s Association of Mataro
´. The investiga-
tion was conducted in accordance with the Helsinki
Declaration of 1964 (2008 revision) and Good Clini-
cal Practice guidelines. All participants gave written
informed consent. Subjects were men and women aged
50–80 years diagnosed with PD according to UK PD
Society Brain Bank Criteria,
26
with disease severity of
Hoehn and Yahr (H&Y) stages I–III,
27
and not receiv-
ing any other cognitive, psychological, speech therapy,
or physical treatment during the study.
Participants were excluded if they had significant
cognitive impairment (Mini-Mental State Examination
<23), below average premorbid intelligence (vocabu-
lary subtest, Wechsler Adult Intelligence Scale-III
[WAIS-III] typical score <40) that would interfere in
learning or comprehension of the program, were on
cholinesterase inhibitors or had changes in their medi-
cation during the study, did not complete 75% of the
training program, had major depression (GDS-15 >
10), or had severe auditory or visual deficits or
another psychiatric/neurological condition.
Design and Procedures
This was a blind multicenter randomized, controlled
trial divided into 5 principal stages (Fig. 1). The first
stage was based on the recruitment of the subjects for
the study. Sociodemographic data, neurological data,
and written informed consent were collected from all
subjects enrolled in the study. During the second
stage, an expert evaluator, blinded to the patients’
group allocation, assessed the cognitive, mood, QOL,
and functional status of the participants. In the third
stage, subjects were randomly assigned to 2 groups:
control (CG) and experimental (CTG). A matched-
pairs design was created in which participants were
blindly allocated to these 2 groups taking the variables
age and vocabulary (WAIS-III) into consideration. In
the fourth stage, 2 trained professionals administered
the training program to both groups. The treatment
group received an individualized CT program, and the
CG received speech therapy group sessions. Finally, at
the end of the 4-week training, subjects from both
groups were administered a blind evaluation, using the
same protocol of neuropsychological, mood, QOL,
and functional tests. Both evaluations and training
were performed during the ON period.
Clinical Assessment
Patients’ full clinical histories were collected. Stand-
ardized neurological assessment included the Unified
Parkinson’s Disease Rating Scale (UPDRS)
28
together
with the H&Y Staging of Parkinson’s Disease.
27
Aspects of functioning and well-being were assessed
using the Parkinson’s Disease Questionnaire (PDQ-
39),
29
and cognitive difficulties in ADLs were eval-
uated using the Cognitive Difficulties Scale (CDS).
30
To control the possible influence of mood on cognitive
performance, all patients completed the 15-item Yes-
avage Geriatric Depression Scale (GDS-15).
31
Neuropsychological Testing
The battery of neuropsychological tests at baseline
and retest included cognitive screening assessed by the
PRATS ET AL.
1252 Movement Disorders, Vol. 26, No. 7, 2011
30-item Mini Mental State Examination
32
and the
Addenbrooke Cognitive Examination.
33
Premorbid
intelligence was determined by the Vocabulary subtest
of the WAIS-III.
34
Attention and working memory
were assessed by the Digits subtest (WAIS-III)
34
and
the first trial of the California Verbal Learning Test
(CVLT-II).
35
Information processing speed was meas-
ured using the written modality of the Symbol-Digit
Modalities Test (SDMT),
36
Trail Making Test–A
(TMT-A),
37
and the Word subtest (Stroop Test).
38
Verbal memory was evaluated using the CVLT-II
35
and the Logical Memory subtest (WMS-III).
39
Learn-
ing was also assessed by the CVLT-II.
35
The Rey
Osterrieth Complex Figure Test (ROCFT)
40
measured
visual memory and visuoconstructive abilities. Visual
spatial abilities were measured by the Line Orientation
subtest from the Repeatable Battery for the Assess-
ment of Neuropsychological Status (RBANS).
41
Two
verbal fluency tasks were administered: phonemic,
using FAS, and semantic, using animals.
42
Frontal
lobe–sensitive tasks were also included and were
assessed by the Tower of London (TOL),
43
Trail Mak-
ing Test–B (TMT-B) ,
37
and the Interference subtest of
the Stroop Test.
38
Treatment
Both groups underwent the same rehabilitation pro-
gram methodology: with a duration of 45 minutes, 3
times a week for 4 weeks (a total of 12 sessions) and,
in addition, exercises to do at home, 1 per week, with
individual tutored sessions once a week.
CT was performed using different therapeutic
modalities, including interactive multimedia software
and paper-and-pencil exercises. Computer-aided train-
ing was supervised by a trained clinical psychologist
using the SmartBrain tool.
44
A platform with 28 activ-
ities was designed based on stimulating specific cogni-
tive domains known to be impaired in PD (attention/
working memory, memory, psychomotor speed, execu-
tive functions, and visuospatial abilities) and nonspe-
cific cognitive exercises (language, simple calculations
skills, and culture). Initially, all patients were started
at a medium difficulty level (level 7). The software
monitored each participant’s performance automati-
cally after each correct/incorrect response. Combined
with computer-aided training, each week CTG partici-
pants received a pack with 20 cognitive homework
exercises designed to stimulate specific and nonspecific
cognitive areas. The speech therapy received by the
CG aimed to make participants’ aware of their speech
and communication difficulties.
Statistical Analysis
Demographic and clinical characteristics at baseline
were compared using a 2-tailed ttest for independent
samples or a 2-sided chi-square test when appropriate.
The effect of the CT treatment on neuropsychological
performances and daily functional scales was analyzed
with repeated-measures ANOVAs (time "treatment
interaction), with treatment groups as the between-
subject factor and the 2 evaluations (pretest and postt-
est) as the within-subject factor. To determine the
effect of MCI on the dependent variables, we used a
2-way ANOVA (MCI "group) on gain scores of the
subjects (posttest/pretest). The level of statistical sig-
nificance was set at .05.
FIG. 1. Stages in the study design.
EFFICACY OF COGNITIVE TRAINING IN PD
Movement Disorders, Vol. 26, No. 7, 2011 1253
Furthermore, to compare the magnitude of the treat-
ment effects on the CTG, standardized effect sizes
(Cohen’s d) were calculated for each variable follow-
ing the Thalheimer and Cook
45
methodology. Follow-
ing to the recommendation of Wilson et al,
46
we
subtracted the CG posttest score from the CTG postt-
est score, and divided this term by the standard devia-
tion of the whole sample at retest. The following
cutoff scores applied: !1.10 to <1.45, very large
effect; !0.75 to <1.10, large effect; !0.40 to <0.75,
medium effect; !0.15 to <0.40, small effect.
Results
From the initial sample of 46, a total of 33 subjects
were randomly assigned to treatment. Only 5 partici-
pants dropped out (2 in the CTG and 3 in the CG)
during the study. Reasons for the dropping out were
not completing the attendance criteria or not partici-
pating in the postevaluation. Among completers, 16
patients received the CT program (CTG) and 12 the
speech therapy program (CG). The diagram flow of
participation can be seen in Figure 2.
The sample included participants from both sexes
(50% male). Their mean age was 65 69.19 years,
mean duration of the disease was 7.5 66.8 years, and
mean years of education was 9 62.9 years. Of the
studied sample, 50% (14 of 28 patients) met Petersen
et al criteria for MCI.
47,48
Subjects classified as having
MCI demonstrated a decrement of more than 1.5 SD
on any cognitive test or subtest. There were no statisti-
cally significant differences between groups at baseline
observation for any of the variables studied (Table 1).
The repeated-measures ANOVA showed a signifi-
cant time "treatment interaction in favor of the CTG
for several neurocognitive variables. The CTG had an
improved performance in 1 of the attention and work-
ing memory measures, the WAIS-III Digit Span For-
ward (F¼5.58, P¼.026). Also, 1 of the measures of
information processing speed showed this expected
interaction, the Stroop Word subtest (F¼16.46, P¼
.000). Both measures of visual memory showed the
expected time "treatment interaction, Immediate (F
¼7.02, P¼.014) and Delayed (F¼4.31, P¼.048)
Recall of the ROCFT. The measure of visuoconstruc-
tive abilities, the Copy of the ROCFT, also showed
our hypothesized interaction (F¼8.95, P¼.006), as
did the measure of visuospatial abilities, the RBANS–
Line Orientation subtest, (F¼10.80, P¼.003).
Moreover, 1 of the verbal fluency measures, the
Semantic–Animals, showed the expected improvement
for the CTG (F¼9.53, P¼.005), as well as 3 of the
executive function measures, the TMT-B (F¼6.44, P
¼.018), the TOL–Total Moves (F¼12.17, P¼
.002), and the TOL–Total Correct (F¼12.21, P¼
.002). However, QOL and functional scales did not
show the expected significant time "treatment inter-
action (Table 2).
The MCI group did not show any significant effect
in the multivariate tests. In the tests of the within-sub-
jects effects, we found a significant interaction MCI "
group in the dependent variables RBANS–Line Orien-
tation (F¼6.264, P<.05), TOL–Total Movements
(F¼4.441, P<.05), and Trail Making Test–B (F¼
4.323, P<.05). This significant interaction occurred
because the experimental treatment more improved
FIG. 2. Flow diagram of subject recruitment and participation in the study. (1) The experimental group participated in an individualized cognitive
training program; (2) the control group received group speech therapy reeducation. Randomization was performed after baseline assessment to
blind investigators.
PRATS ET AL.
1254 Movement Disorders, Vol. 26, No. 7, 2011
the performance of the subjects with MCI than those
without MCI.
Complementary analysis including the center from
where the subjects were recruited as a second
between-subject factor showed that the differences
between the subjects from both centers did not affect
the significant time "treatment interaction found.
Effect Sizes of Improvement
Table 2 also shows the effect sizes of improvement
for the differences between groups. Cohen’s dvalue
confirmed the significant interaction found in Seman-
tic–Animals, TOL–Total Correct, and TOL–Total
Moves, indicating a very large effect from CT. The
Stroop Word subtest, and the WAIS-III Digit Span
Forward, which also showed a significant time "
treatment interaction, showed a large effect from CT.
The significance found with the TMT-B was confirmed
by a medium effect size, and the RBANS–Line Orien-
tation test only showed a small effect after CT.
Discussion
Cognitive impairment is frequent in nondemented
PD. Similar to in other studies,
3–5
in our sample 50%
met criteria for MCI. CT has proved to be a useful
and efficient tool in the management of cognitive
impairment of other pathological conditions. As very
few studies have been conducted in PD, we aimed to
determine the efficacy of a CT program on cognitive
performance and QOL in nondemented PD patients.
Our findings suggest that an intensive CT program
(3 times a week for 4 weeks) can be a useful tool in
improving cognitive performance in PD patients.
Improved cognitive performance was observed in CTG
participants compared with controls in attention, in-
formation processing speed, memory, visuospatial and
visuoconstructive abilities, semantic verbal fluency,
and executive functions. Thus, our study supports the-
ories that suggest CT may activate mechanisms of cer-
ebral plasticity and slow down the progression of
cognitive manifestations of the disease.
49,50
Future
investigations with functional neuroimaging methods
such as positron emission tomography and functional
magnetic resonance should be encouraged. Such stud-
ies may be useful in assessing CT effectiveness and
explaining the cerebral consequences of plasticity asso-
ciated with PD.
Even though classic tests of executive functions, such
as the TMT, have been widely accepted as good predic-
tors of functional status,
51–53
the observed cognitive
changes were not shown in a change of functional
measures. It is worth noting that specific functional
scales sensitive to detecting subtle cognitive change for
PD do not exist. However, a recent study demonstrated
how a functional scale designed for Alzheimer’s disease
could also be used to assess functional changes in PD
with MCI.
8
Our functional scale was a self-adminis-
tered measure designed to assess cognitive difficulties
TABLE 1. Demographic and clinical data at baseline of patients
in the CTG and CG groups
Variable
Group Statistics
CTG CG v
2a
P
Sex (male/female), n 7/9 7/5 0.58 .45
t
b
P
Age, mean (SD) 64.75 (9.19) 65.42 (9.60) $0.19 .85
Year of diagnosis, mean (SD) 2002.06 (4.58) 2001.17 (9.63) 0.33 .75
Years of evolution, mean (SD) 6.94 (4.58) 8.25 (9.22) $0.50 .62
Hoehn & Yahr, mean (SD) 2.37 (0.76) 2.25 (0.78) 0.49 .63
Years of education, mean (SD) 9.88 (2.94) 9.50 (3.09) 0.33 .75
WAIS-III Vocabulary,
c
mean (SD) 58.19 (6.57) 55.33 (8.38) 1.42 .17
v
2a
P
Mild cognitive impairment,
d
n (%) 8 (50%) 6 (50%) 0 1
a
Two-sided chi-square test;
b
2-tailed tfor independent samples;
c
adjusted by age;
d
according to Petersen’s et al.
45
Criteria: (1) presence of a subjective memory complaint, (2) preserved general
intellectual functioning as estimated by performance on a vocabulary test, (3) decrement of more than 1.5 SD on
any cognitive test or subtest, (4) intact ability to perform activities of daily living, and (5) absence of dementia.
CTG, cognitive training group; CG, control group; WAIS-III Vocabulary, Wechsler Adult Intelligence Scale–III,
Vocabulary subtest.
EFFICACY OF COGNITIVE TRAINING IN PD
Movement Disorders, Vol. 26, No. 7, 2011 1255
in ADLs. The finding of deficits in meta-memory found
in PD patients
54
may suggest questioning the accuracy
of these measures.
55
Asking a caregiver or family mem-
ber to fill out questionnaires could be useful in future
investigations. In addition, CT programs focused spe-
cifically on the training of more ecological tasks could
also help improve ADLs of PD patients.
56
No significant statistical improvements were
observed in terms of self-reported QOL in CTG sub-
jects. This outcome could have resulted from QOL
TABLE 2. Neurocognitive performances, measures of functional scales, and effect size of improvement in the CT and
CG groups at baseline and retest
Neurocognitive areas
Baseline Retest
Statistics (ANOVA)CTG (n ¼16) CG (n ¼12) CTG (n ¼16) CG (n ¼12)
Test—measure Mean (SD) Mean (SD) Mean (SD) Mean (SD) F
a
P
a
d
b
Cognitive screening
MMSE 28.13 (1.31) 27.58 (1.44) 28.56 (1.03) 27.42 (1.93) 1.21 .28 0.8
ACE 89.56 (8.05) 84.58 (9.03) 92.88 (6.64) 84.92 (6.02) 3.00 .09 1.29
Attention and working memory
WAIS III–Digit Span 15.44 (3.55) 14.00 (5.01) 16.44 (3.27) 13.08 (3.75) 2.28 .14 1
WAIS III–Digit Span Forward 5.75 (1.18) 5.67 (1.07) 6.38 (0.96) 5.25 (1.54) 5.58 .03 0.94
WAIS III–Digit Span Backward 4.75 (1.12) 4.08 (0.67) 58.06 (11.16) 53.67 (7.57) 1.12 .30 0.47
CVLT II–List A1 4.75 (1.77) 5.58 (1.51) 7.25 (1.81) 6.83 (1.40) 3.86 .06 0.26
Information processing speed
SDMT 29.75 (14.23) 27.36 (12.33) 31.13 (11.75) 26.09 (11.73) .62 .44 0.45
TMT-A 66.38 (39.47) 60.55 (34.31) 54.44 (22.79) 62.55 (38.84) 3.50 .07 0.28
Stroop Test–Word subtest 98.88 (18.22) 101.00 (21.99) 105.94 (15.77) 88.45 (21.45) 16.46 .00 1
Verbal memory
CVLT-II–Short-Delay Free Recall 9.88 (3.26) 8.00 (1.41) 57.50 (8.56) 50.42 (8.38) 2.87 .10 0.87
CVLT-II–Long-Delay Free Recall 9.88 (2.91) 8.50 (1.68) 11.69 (2.24) 10.25 (2.56) 0.00 .95 0.63
WMS-III–Logical Memory I 34.38 (12.53) 29.83 (5.73) 40.13 (12.96) 31.67 (7.85) 1.63 .21 0.79
WMS-III–Logical Memory II 20.56 (7.34) 16.83 (5.61) 25.63 (7.84) 19.42 (7.44) 1.53 .23 0.84
Learning
CVLT-II–List A Total 42.94 (10.59) 41.00 (6.69) 53.63 (9.97) 48.42 (8.67) 1.22 .28 0.57
Visual memory
ROCFT–Immediate Recall 15.38 (5.17) 18.54 (5.53) 20.34 (7.10) 20.04 (5.17) 7.02 .01 0.05
ROCFT–Delayed Recall 12.84 (7.47) 17.25 (5.06) 18.84 (8.47) 19.83 (5.65) 4.31 .05 0.14
Visuoconstructive abilities
ROCFT –Copy 30.75 (6.39) 33.88 (4.05) 33.00 (5.30) 33.13 (3.02) 8.95 .01 0.03
Visuospatial Abilities
RBANS–Line Orientation 16.25 (3.42) 17.83 (1.85) 17.88 (2.19) 16.92 (3.48) 10.80 .00 0.35
Verbal fluency
Phonemic–FAS 38.69 (12.34) 33.33 (11.44) 42.25 (9.79) 33.92 (10.51) 3.43 .08 0.86
Semantic–Animals 16.06 (5.21) 15.42 (3.00) 20.94 (4.65) 14.75 (5.51) 9.53 .01 1.28
Executive functions
TMT-B 141.56 (96.42) 149.30 (131.22) 114.81 (66.45) 161.20 (147.02) 6.44 .02 0.46
TOL–Total Moves 43.56 (22.72) 35.90 (17.54) 22.25 (12.69) 37.10 (15.74) 12.17 .00 1.11
TOL–Total Correct 3.25 (1.81) 3.70 (2.00) 5.50 (1.93) 3.20 (2.30) 12.21 .00 1.15
TOL–Rules Violations 1.36 (1.79) 1.40 (2.84) 0.56 (1.09) 0.70 (1.06) 0.01 .91 0.13
Stroop Test–Interference 4.00 (5.15) 3.00 (6.02) 5.44 (7.92) 6.20 (6.43) 0.37 .55 0.11
Functional Scales
Quality of life
PDQ-39 47.94 (21.36) 42.83 (20.67) 50.25 (26.72) 34.08 (20.57) 2.20 .15 0.69
Mood
GDS-15 2.69 (2.15) 2.42 (2.31) 2.56 (2.48) 2.17 (1.95) 0.02 .90 0.18
Cognitive difficulties in ADLs
CDS 44.63 (25.51) 40.83 (22.38) 41.63 (24.24) 39.42 (24.91) 0.06 .81 0.09
The ‘‘baseline’’ and ‘‘retest’’ columns show the raw scores of evaluations and the differences between pretest and posttest calculated with ANOVA.
a
ANOVA;
b
Cohen’s effect-size test. CTG, cognitive training group; CG, control group; ACE, Addenbrooke’s Cognitive Examination; MMSE, Mini–Mental State
Examination; WAIS-III, Wechsler Adult Intelligence Scale–III; CVLT-II, California Verbal Learning Test–II; SDMT, Symbol Digit Modalities Test; TMT-A, Trail
Making Test, part A; WMS-III, Wechsler Memory Scale–III; ROCFT, Rey-Osterrieth Complex Figure Test; RBANS, Repeatable Battery for the Assessment of
Neuropsychological Status. TMT-B, Trail Making Test, part B; TOL, Tower of London; PDQ-39, Parkinson’s Disease Questionnaire; GDS-15, 15-item Geriatric
Depression Scale; CDS, Cognitive Difficulties Scale.
PRATS ET AL.
1256 Movement Disorders, Vol. 26, No. 7, 2011
being a multidimensional construct affected by various
factors
57–59
that were not controlled in this study.
Alternatively, the outcome may be because of the
short duration of the treatment. An extended training
program may be needed to have a meaningful impact
on well-being and QOL. Likewise, improvement in
mood was not observed, but this was not expected in
our study because most of our patients were not
depressed at baseline.
Our main study limitation was its relatively small
sample size, which may have subtracted external valid-
ity from the obtained results. However, our blind,
randomized, controlled trial design ensured internal
validity of the results. Previous studies of CT in PD
have also achieved positive results with a similar or
smaller sample size.
21,22
Another important limitation to the study was that we
were not able to establish mid- and long-term effects (>6
months). Because this follow-up evaluation was not per-
formed, it was not possible to observe if the effects of this
training persisted over time or if the effect of improve-
ment was mainly associated with the CT program.
Despite the methodological limitations described
above, several major strengths distinguish this study.
First, we used a comprehensive standardized battery that
included well-known instruments used in PD. Second,
there were no biased researchers in this study, protecting
against selection bias. Third, based on previous investiga-
tions, we conducted a brief and intensive training pro-
gram to improve clinical outcomes and cost
effectiveness.
19
Finally, the small number of dropouts
indicates high adherence to therapy in the intensive train-
ing program, proving it to be practical and of easily
implemented in nondemented PD patients.
Further studies are necessary to evaluate the efficacy
of CT and at which moment in the course of the dis-
ease it is better to start CT programs in PD patients.
These studies should also determine which strategies
and techniques are more efficient in the management
of cognitive deficits in PD and if these skills translate
to improvements in daily life and QOL. Larger studies
with follow-up periods are needed to verify if the
effects of this training persist over time. Nonetheless,
our findings suggest that intensive CT may be an effec-
tive tool for improving cognitive functions in nonde-
mented PD patients.
Acknowledgment: We extend our sincere appreciation to all the patients
who participated in this study, the Parkinson Association of Mataro
´, the
health care staff who helped with recruitment, especially to Lluı
¨sa Ara
´n
and Paola Quispe, and the trainers, research associates, and clinicians
who contributed to the design of the study and participated in it. We
thank Pauline Gillies (from Edinburgh University) for English reviewing.
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... Subsequently, we assessed 130 full-text articles for eligibility and ten of these fulfilled inclusion criteria. A list of the excluded studies with reasons is provided in Appendix C. Records were combined with four eligible studies from our previous review (Cerasa et al., 2014;Edwards et al., 2013;París et al., 2011;Zimmermann et al., 2014) and two additional studies were identified through manual search (NCT01156714; van de Weijer et al., 2020). One study that compared outcomes for CCT with or without transcranial direct current stimulation (tDCS) was split into two separate comparisons with three independent arms each (Lawrence et al., 2018), resulting in a total of 17 RCTs in the meta-analysis ( Fig. 1). ...
... Participant disease severity ranged from Hoehn & Yahr stages 1-4. Nine studies focused on participants with cognitive impairment (Bernini et al., 2019(Bernini et al., , 2021Cerasa et al., 2014;De Luca et al., 2019;Lawrence et al., 2018;Maggio et al., 2018;París et al., 2011;van de Weijer et al., 2020;Vlagsma et al., 2020). Five studies were from Italy (Bernini et al., 2019(Bernini et al., , 2021Cerasa et al., 2014;De Luca et al., 2019;Maggio et al., 2018), two were from Australia (Lawrence et al., 2018;Walton et al., 2018), the Netherlands (van de Weijer et al., 2020;Vlagsma et al., 2020) and the United States (Edwards et al., 2013;NCT01156714) and the remaining studies were from Brazil (Ferraz et al., 2018), Finland (Fellman et al., 2018), Germany (Ophey et al., 2020), Switzerland (Zimmermann et al., 2014) and Spain (París et al., 2011). ...
... Nine studies focused on participants with cognitive impairment (Bernini et al., 2019(Bernini et al., , 2021Cerasa et al., 2014;De Luca et al., 2019;Lawrence et al., 2018;Maggio et al., 2018;París et al., 2011;van de Weijer et al., 2020;Vlagsma et al., 2020). Five studies were from Italy (Bernini et al., 2019(Bernini et al., , 2021Cerasa et al., 2014;De Luca et al., 2019;Maggio et al., 2018), two were from Australia (Lawrence et al., 2018;Walton et al., 2018), the Netherlands (van de Weijer et al., 2020;Vlagsma et al., 2020) and the United States (Edwards et al., 2013;NCT01156714) and the remaining studies were from Brazil (Ferraz et al., 2018), Finland (Fellman et al., 2018), Germany (Ophey et al., 2020), Switzerland (Zimmermann et al., 2014) and Spain (París et al., 2011). Six studies (38%) had a high risk of bias, seven (44%) had some concerns and three (19%) had a low risk of bias (Table 1, Appendix D). ...
Article
Cognitive impairment is a central non-motor symptom of Parkinson's disease (PD), and there are no established treatments. Computerized cognitive training (CCT) is a safe and efficacious strategy but its efficacy in PD is unclear. We aimed to investigate the efficacy of CCT on cognitive, psychosocial and daily function, and assess potential effect moderators in people with PD without dementia. Randomized controlled trials of CCT were included in multivariate meta-analyses and meta-regressions. Seventeen studies (16 trials) encompassing 679 participants were included. The pooled effect of CCT relative to control was small and statistically significant for overall cognitive function (g=0.16; 95% CI 0.02-0.29). There was robust evidence for benefit on clinical measures of global cognition across 10 trials (g=0.33; 95% CI 0.19-0.48), especially in PD with mild cognitive impairment (PD-MCI), as well as on individual cognitive domains. Greater CCT dose and PD-MCI population were associated with larger effect sizes, but no statistically significant differences were found between subgroups. There was no significant difference in the efficacy of home-based compared to supervised training. Our findings suggest that CCT is associated with cognitive benefits in PD, including when delivered remotely. Larger, well-powered trials are warranted to examine what specific CCT regimens are most likely to promote cognitive and everyday functioning in the long-term.
... All studies but one [25] were randomized clinical trials. In the included studies, patients were enrolled if they: i) had an impairment in an objective cognitive test of executive functions but were not demented as assessed with the scales for outcomes in PD cognition scale [26]; ii) had a mini mental state examination (MMSE) score > 24 and absence of diagnosis of dementia [27,28]; or iii) had a mild to moderate cognitive impairment but not dementia [29,30]; iv) had a MMSE < 25 but they had not dementia [31][32][33]; v) had a diagnosis of MCI in accordance with Petersen's criteria [34]. Four studies mentioned as inclusion criteria an overall absence of dementia [25,[35][36][37]. ...
... One study included only participants with MCI using established diagnostic criteria [28] and 1 study enrolled participants with single or multiple domain MCI including executive dysfunction [38]. With respect to the treatment, 7 studies compared cognitive trainings with other control conditions [27,29,31,34,36]. One study used the cognitive training as control condition whereas the experimental group underwent to a virtual reality based training [30]. ...
... Another group of studies compared the effect of domain specific cognitive rehabilitation with not specific cognitive trainings [26] or active control conditions [37] (see Table 1). With respect to studies included in the analyses, 6 studies where included for global cognitive functioning [28,[30][31][32]34,38], 8 studies contributed to the analysis of attention [25,26,28,30,31,34,35,38]; 9 studies were included in the meta-analysis for executive functions [25,26,28,30,31,34,35,37,38]; 5 studies contributed to the analysis of language [30,31,33,34,38]; 8 studies were used for the long term memory [25,30,31,[33][34][35]37,38]; 7 studies contributed to the analysis relative to short term memory [30,31,[33][34][35]37,38]; 5 studies were used for visuospatial abilities [27,30,31,34,38] and 9 studies contributed to the analysis of the clinical scales [25][26][27][28]31,[33][34][35]37] (Table 1 of the supplementary materials). ...
Article
Background and objectives: Cognitive symptoms are common in Parkinson's disease (PD) and affect patients' quality of life. Pharmacological interventions often do not improve such deficits that might benefit of cognitive rehabilitation. However, previous meta-analysis on this topic reported inconsistent results. Clarifying the efficacy of cognitive rehabilitation would be pivotal to optimize treatment and reduce care's costs. This meta-analysis aims at determining whether current literature lays in favor of the effectiveness of cognitive rehabilitation in PD and at understanding whether its effect might change depending on the trained cognitive domain. Methods: We searched online databases for studies concerning cognitive rehabilitation in PD. Fourteen studies encompassing 767 participants were included. Analyses were conducted for each cognitive domain separately, examining several neuropsychological measures for each function. Results: We found that rehabilitation improves global cognition, executive functions, and long- and short-term memory. Conclusion: The current body of research indicates that cognitive rehabilitation improves specific cognitive deficits in PD and that it should be tailored on patients' specific impairments. These interventions should be employed considering that not all the cognitive domains might benefit of a cognitive training. Finally, the high heterogeneity among studies suggests the need for more controlled clinical trials.
... Unfortunately, there have been few randomized controlled trials of cognitive training in PD but those that have been performed generally report at least some positive effects. In one blind randomized control study, a computerized training program was used to stimulate specific cognitive domains known to be impaired in PD (attention/working memory, memory, psychomotor speed, executive functions, and visuospatial abilities) as well as non-specific cognitive exercises (ex., language, calculations, culture), while control subjects received only speech therapy (Paris et al., 2011). Compared to the control group, the patients that received cognitive training showed improved performance on tests of attention, information processing speed, memory, visuospatial and visuoconstructive abilities, semantic verbal fluency, and executive functions (Paris et al., 2011). ...
... In one blind randomized control study, a computerized training program was used to stimulate specific cognitive domains known to be impaired in PD (attention/working memory, memory, psychomotor speed, executive functions, and visuospatial abilities) as well as non-specific cognitive exercises (ex., language, calculations, culture), while control subjects received only speech therapy (Paris et al., 2011). Compared to the control group, the patients that received cognitive training showed improved performance on tests of attention, information processing speed, memory, visuospatial and visuoconstructive abilities, semantic verbal fluency, and executive functions (Paris et al., 2011). Patients did not report any observable improvements in quality of life or cognitive function related to daily activities of living (Paris et al., 2011), however the 4 weeks of cognitive training used in this study may have produced changes in testing on sensitive neuropsychological tests but may not have been long enough to result in meaningful changes detected by the patients. ...
... Compared to the control group, the patients that received cognitive training showed improved performance on tests of attention, information processing speed, memory, visuospatial and visuoconstructive abilities, semantic verbal fluency, and executive functions (Paris et al., 2011). Patients did not report any observable improvements in quality of life or cognitive function related to daily activities of living (Paris et al., 2011), however the 4 weeks of cognitive training used in this study may have produced changes in testing on sensitive neuropsychological tests but may not have been long enough to result in meaningful changes detected by the patients. ...
Article
Impairment in various aspects of cognition is recognized as an important non-motor symptom of Parkinson's disease (PD). Mild cognitive impairment in PD (PD-MCI) is common in non-demented PD patients and is often associated with severity of motor symptoms, disease duration and increasing age. Further, PD-MCI can have a significant negative effect on performance of daily life activities and may be a harbinger of development of PD dementia. Thus, there is significant interest in developing therapeutic strategies to ameliorate cognitive deficits in PD and improve cognitive functioning of PD patients. However, due to significant questions that remain regarding the pathophysiology of cognitive dysfunction in PD, remediation of cognitive dysfunction in PD has proven difficult. In this paper, we will focus on PD-MCI and will review some of the current therapeutic approaches being taken to try to improve cognitive functioning in patients with PD-MCI.
... Several CT programs over the last decade have also utilized a combination of "pen and paper" and computer-based delivery. París et al. (2011) were the first to conduct a study of CT in PD in which a control group received a placebo intervention (París et al., 2011). In this study, over the course of 4 weeks, the experimental group (n = 16) received 12 × 45 min CT sessions using interactive multimedia software (SmartBrain tool), as well as weekly paper and pencil-based homework exercises and a weekly tutoring session. ...
... Several CT programs over the last decade have also utilized a combination of "pen and paper" and computer-based delivery. París et al. (2011) were the first to conduct a study of CT in PD in which a control group received a placebo intervention (París et al., 2011). In this study, over the course of 4 weeks, the experimental group (n = 16) received 12 × 45 min CT sessions using interactive multimedia software (SmartBrain tool), as well as weekly paper and pencil-based homework exercises and a weekly tutoring session. ...
... The control group (n = 12) received speed therapy. Following the intervention, the CT group significantly improved in several cognitive domains (see Table 2 for summary outcomes) (París et al., 2011). However, there were no significant improvements in ADL or self-rated QoL (París et al., 2011), suggesting that, while CT may be beneficial for improvements on specific neuropsychological tests, these skills may not generalize to improvements in everyday functioning. ...
Article
Full-text available
Cognitive dysfunction, primarily involving impairments in executive function, visuospatial function and memory, is one of the most common non-motor symptoms of Parkinson’s disease (PD). Currently, the only pharmacological treatments available for the treatment of cognitive dysfunction in PD provide variable benefit, making the search for potential non-pharmacological therapies to improve cognitive function of significant interest. One such therapeutic strategy may be cognitive training (CT), which involves the repetition of standardized tasks with the aim of improving specific aspects of cognition. Several studies have examined the effects of CT in individuals with PD and have shown benefits in a variety of cognitive domains, but the widespread use of CT in these individuals may be limited by motor impairments and other concerns in study design. Here, we discuss the current state of the literature on the use of CT for PD and propose recommendations for future implementation. We also explore the potential use of more recent integrative, adaptive and assistive technologies, such as virtual reality, which may optimize the delivery of CT in PD.
... However, this mental acceleration does not seem to translate to daily function as patients in both conditions reported minor subjective improvement after the intervention, but without group differences. Previous studies that assessed the effects of CT on subjective complaints in PD found small improvements [9,20] or null results [21][22][23]. The sensitivity of the PD-CFRS in measuring treatment effectsas opposed to its sensitivity to measuring clinically relevant cognitive decline [24,25] has not yet been studied and our PD sample showed little variation in the total score at baseline. ...
Article
Full-text available
Introduction Cognitive training (CT) has been proposed as a treatment option for cognitive impairment in Parkinson's disease (PD). We aimed to assess the efficacy of adaptive, computerized CT on cognitive function in PD. Methods In this double-blind, randomized controlled trial we enrolled PD patients that experienced substantial subjective cognitive complaints. Over a period of eight weeks, participants underwent 24 sessions of computerized multi-domain CT or an active control intervention for 45 min each (randomized 1:1). The primary outcome was the accuracy on the Tower of London task; secondary outcomes included effects on other neuropsychological outcomes and subjective cognitive complaints. Outcomes were assessed before and after training and at six-months follow-up, and analyzed with multivariate mixed-model analyses. Results The intention-to-treat population consisted of 136 participants (n = 68 vs. n = 68, age M: 62.9y, female: 39.7%). Multivariate mixed-model analyses showed no group difference on the Tower of London accuracy corrected for baseline performance (n = 130): B: −0.06, 95% CI: −0.27 to 0.15, p = 0.562. Participants in the CT group were on average 0.30 SD (i.e., 1.5 s) faster on difficulty load 4 of this task (secondary outcome): 95% CI: −0.55 to −0.06, p = 0.015. CT did not reduce subjective cognitive complaints. At follow-up, no group differences were found. Conclusions This study shows no beneficial effect of eight-week computerized CT on the primary outcome (i.e., planning accuracy) and only minor improvements on secondary outcomes (i.e., processing speed) with limited clinical impact. Personalized or ecologically valid multi-modal intervention methods could be considered to achieve clinically meaningful and lasting effects.
... Various interventions are provided with the intention of delaying the onset of severe cognitive impairments in PD patients to sustain their quality of life as much as possible. While a pharmacological approach (cholinesterase inhibitors) has not been found to yield any clear cognitive improvement [9], cognition-specific training [10] as well as nonspecific video-game training [11][12][13][14][15][16] or psychomotor and endurance training [17] has been found to improve cognitive abilities in PD patients. In more detail, physical exercise was reported to preserve brain health and cognitive functioning in normal and diseased aging [18][19][20][21][22][23] by improving spatial learning and memory [24,25], as well as executive functioning [19,[26][27][28][29][30][31]. ...
Article
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Background: Dementia is the one of the most common and prominent disease in the elderly person that results in the Cognitive interventions. In this study, we aim to conceptualize the cognitive intervention for older adults with and without cognitive dysfunction and to clarify the heterogeneity existing in this literature field by determining the main variables implicated. Methods: We conducted a study analysis using previous literature highlighting the significant data reporting empirical results from cognitive intervention for healthy older adults and other seniors with different types of dementia. Each paper was reviewed in terms of compensatory cognitive training, cognitive remediation, enrichment, cognitive activation, brain training, cognitive stimulation, cognitive training, and cognitive rehabilitation. The research analysis was performed following rigorous inclusion and exclusion criteria with the purpose of collecting relevant answers to our research questions. Results: We included a total of 168 studies in our review. Our findings indicated heterogeneity regarding methods, concepts, and procedures. Additionally, the values were integrated using different information existing in this field. Conclusion: In conclusion, we highlighted that this is the first review that clarify the discrepancy of various existing definitions, methods, and procedures, as well as the overlapping information in the cognitive interventions.
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While motor symptoms are the most recognized features of Parkinson's disease (PD), cognitive dysfunction is a key determinant of consequences of PD in real-life. In this chapter we review important domains where cognitive dysfunction negatively impacts the lives of people with PD (PwPD), such as difficulties in occupational and social life, and instrumental ADLs such as driving. Early loss of employment has important effects for PwPD, their families, and society. PwPD experience higher rates of family and social discord as well as important changes in their social roles. These processes are largely mediated through cognitive dysfunction, particularly difficulties processing and understanding emotions, decreased attention, and executive dysfunction. Cognitive dysfunction is also an important mediator of driving impairments, which contributes to decreased independence in PwPD. Finally, we briefly review the costs associated with cognitive impairment in PD. Both indirect and direct costs for PwPD with cognitive impairment are substantially higher than for PwPD with normal cognition.
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Introduction: Parkinson’s disease (PD) is associated with a range of cognitive deficits. Few studies have carefully examined the subtle impacts of PD on cognition among patients who do not meet formal criteria for MCI or dementia. The aim of the current study was thus to describe the impact of PD on cognition in those without cognitive impairment in a well-characterized cohort. Methods: Non-cognitively impaired participants (122 with PD, 122 age- and sex-matched healthy volunteers) underwent extensive cognitive testing. Linear regression analyses compared diagnostic group performance across cognitive measures. For cognitive tasks that were significantly different between groups, additional analyses examined group differences restricting the group inclusion to PD participants with mild motor symptoms or disease duration less than 10 years. Results: Processing speed and semantic verbal fluency were significantly lower in the PD group (B = −3.77, 95% CIs [−5.76 to −1.77], p < .001, and B = −2.02, 95% CIs [−3.12, −0.92], p < .001, respectively), even after excluding those with moderate to severe motor symptoms (B = −2.73, 95% CIs [−4.94 to −0.53], p = .015 and B = −2.11, 95% CIs [−3.32 to −0.91], p < .001, respectively) or longer disease duration (B = −3.89, 95% CIs [−6.14 to −1.63], p < .001 and B = −1.58, 95% CIs [−2.78 to −0.37], p = .010, respectively). Semantic verbal fluency remained significantly negatively associated with PD diagnosis after controlling for processing speed (B = −1.66, 95% CIs [−2.79 to −0.53], p = .004). Conclusions: Subtle decline in specific cognitive domains may be present among people diagnosed with PD but without evidence to support a formal cognitive diagnosis. These results suggest the importance of early awareness of the potential for diminishing aspects of cognition in PD even among those without mild cognitive impairment or dementia.
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Parkinson disease (PD) is the second most common neurodegenerative disorder, affecting >1% of the population ≥65 years of age and with a prevalence set to double by 2030. In addition to the defining motor symptoms of PD, multiple non-motor symptoms occur; among them, cognitive impairment is common and can potentially occur at any disease stage. Cognitive decline is usually slow and insidious, but rapid in some cases. Recently, the focus has been on the early cognitive changes, where executive and visuospatial impairments are typical and can be accompanied by memory impairment, increasing the risk for early progression to dementia. Other risk factors for early progression to dementia include visual hallucinations, older age and biomarker changes such as cortical atrophy, as well as Alzheimer-type changes on functional imaging and in cerebrospinal fluid, and slowing and frequency variation on EEG. However, the mechanisms underlying cognitive decline in PD remain largely unclear. Cortical involvement of Lewy body and Alzheimer-type pathologies are key features, but multiple mechanisms are likely involved. Cholinesterase inhibition is the only high-level evidence-based treatment available, but other pharmacological and non-pharmacological strategies are being tested. Challenges include the identification of disease-modifying therapies as well as finding biomarkers to better predict cognitive decline and identify patients at high risk for early and rapid cognitive impairment. Cognitive impairment is common in patients with Parkinson disease and ranges in severity. This Primer reviews the epidemiology, pathophysiology, diagnosis and treatment of cognitive impairment in Parkinson disease and describes the effects on patient quality of life and the future outlook for the field.
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The aim of the study was to ascertain the prevalence of sleep and daytime disorders in a non-selected group of patients suffering from Parkinson's disease. A self-administered questionnaire focused on sleep and daytime disorders was posted to 130 patients regularly consulted for Parkinson's disease. Filled in questionnaires were returned by 107 patients, of which: 46 were females and 61 males, with an average age of 61 years (±8), with Parkinson's disease duration of 10 years (±5) an average. The patients were classified as stages 1 to 4 (average 2.5±0.6) on the Hoehn and Yahr scale. The results confirm a very frequent occurrence of dyssomnia in Parkinson's disease patients (78%). The ratio of patients having symptoms suggesting REM sleep behaviour disorders - 50% - is high. 36% of patients feel subjective problems while falling asleep. Restless legs before falling asleep are stated by 49% patients. Snoring is reported by 30% patients, 13% patients state problems with apnoic pauses during sleep. The average number of awakenings reported subjectively is 2.3 per night (±1.4).
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Several recent studies have shown that dementia is common in Parkinson's disease (PD), and that in some patients, cognitive impairment occurs even at the time of diagnosis. The point prevalence of dementia in PD is close to 30% and the incidence rate is increased 4–6 times as compared to controls. The cumulative prevalence is very high, at least 75% of PD patients who survive for more than 10years will develop dementia. The mean time from onset of PD to dementia is approximately 10years. However, there are considerable variations, and some patients develop dementia early in the disease course. Earlier onset of dementia is associated with more structural brain changes. The most established risk factors for early dementia are old age, severity of motor symptoms, in particular postural and gait disturbances, mild cognitive impairment and visual hallucinations. The genetic contributions to dementia are currently not clear and need to be explored in future studies.