Blind Randomized Controlled Study of the Efﬁcacy of Cognitive
Training in Parkinson’s Disease
Anna Prats Parı
´s, MS, PhDc,
Heidi Guerra Saleta, PhDc,
Maria de la Cruz Crespo Maraver, PhDc,
Emmanuel Silvestre, PhD,
Maite Garolera Freixa, PhD,
Cristina Petit Torrellas, BA,
Silvia Alonso Pont, BA,
Marc Fabra Nadal, MS,
Sheila Alcaine Garcia, BA,
Maria Victoria Perea Bartolome
Valentina Ladera Ferna
˜ol, MD, PhD
Unitat de Parkinson i Trastorns del Moviment, Centro Me
´dico Teknon. Barcelona, Spain
`noma de Barcelona, Dpto. Biologı
´a Celular, Fisiologı
´a e Inmunologı
´a, Instituto de Neurociencias (INc), Barcelona, Spain
Universidad de Salamanca, Facultad de Psicologı
´a, Dpto. Psicologı
´a y Metodologı
´a. Salamanca, Spain
´de Salut Mental, Fundacio
´Althaia, Manresa, Spain
Silvestre Hispanic Market Research & Services, Rocky Hill, Connecticut, USA
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
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 inParkinson’sdisease.V
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).
lence of dementia in PD is close to 30% and is 6
times higher than that in the general population.
addition, approximately 19%–53% of nondemented
PD patients suffer from mild cognitive impairment
Cognitive impairment in PD is characterized by deﬁ-
cits in executive functions, attention/working memory,
speed of information processing, visuospatial abilities,
and has important clinical consequences
for patient management. MCI and dementia in
PD have been linked to difﬁculties in activities of
daily living (ADLs).
Dementia has also been associ-
ated with rapid motor and functional decline,
and risk of
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
*Correspondence to: A
˜ol, Unidad de Parkinson y
Trastornos del Movimiento, Centro Me
´dico Teknon, Pso. Bonanova 26,
Barcelona, Spain. 08022; email@example.com
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
Published online 25 March 2011 in Wiley Online Library
(wileyonlinelibrary.com). DOI: 10.1002/mds.23688
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,
Alzheimer’s disease and demen-
and, more recently, MCI.
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.
The ﬁrst study on CT in PD patients (Sinforiani
) 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
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-
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
nute sessions per week for 4 weeks) to achieve more
clinical and cost-effective results.
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
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,
with disease severity of
Hoehn and Yahr (H&Y) stages I–III,
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.
Patients’ full clinical histories were collected. Stand-
ardized neurological assessment included the Uniﬁed
Parkinson’s Disease Rating Scale (UPDRS)
with the H&Y Staging of Parkinson’s Disease.
Aspects of functioning and well-being were assessed
using the Parkinson’s Disease Questionnaire (PDQ-
and cognitive difﬁculties in ADLs were eval-
uated using the Cognitive Difﬁculties Scale (CDS).
To control the possible inﬂuence of mood on cognitive
performance, all patients completed the 15-item Yes-
avage Geriatric Depression Scale (GDS-15).
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
Addenbrooke Cognitive Examination.
intelligence was determined by the Vocabulary subtest
of the WAIS-III.
Attention and working memory
were assessed by the Digits subtest (WAIS-III)
the ﬁrst trial of the California Verbal Learning Test
Information processing speed was meas-
ured using the written modality of the Symbol-Digit
Modalities Test (SDMT),
Trail Making Test–A
and the Word subtest (Stroop Test).
Verbal memory was evaluated using the CVLT-II
and the Logical Memory subtest (WMS-III).
ing was also assessed by the CVLT-II.
Osterrieth Complex Figure Test (ROCFT)
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).
verbal ﬂuency tasks were administered: phonemic,
using FAS, and semantic, using animals.
lobe–sensitive tasks were also included and were
assessed by the Tower of London (TOL),
ing Test–B (TMT-B) ,
and the Interference subtest of
the Stroop Test.
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.
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.
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
ing to the recommendation of Wilson et al,
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.
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.
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
PRATS ET AL.
1254 Movement Disorders, Vol. 26, No. 7, 2011
the performance of the subjects with MCI than those
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.
Cognitive impairment is frequent in nondemented
PD. Similar to in other studies,
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.
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,
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
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
CTG CG v
Sex (male/female), n 7/9 7/5 0.58 .45
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
mean (SD) 58.19 (6.57) 55.33 (8.38) 1.42 .17
Mild cognitive impairment,
n (%) 8 (50%) 6 (50%) 0 1
Two-sided chi-square test;
2-tailed tfor independent samples;
adjusted by age;
according to Petersen’s et al.
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,
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
may suggest questioning the accuracy
of these measures.
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.
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
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
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
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
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
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
ROCFT –Copy 30.75 (6.39) 33.88 (4.05) 33.00 (5.30) 33.13 (3.02) 8.95 .01 0.03
RBANS–Line Orientation 16.25 (3.42) 17.83 (1.85) 17.88 (2.19) 16.92 (3.48) 10.80 .00 0.35
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
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
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
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.
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
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.
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
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
health care staff who helped with recruitment, especially to Lluı
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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