Vol.1, No.1, 1-4 (2012) Advances in Parkinson’s Disease
Should gait speed be included in the clinical evalua-
tion of Parkinson’s disease?
Joe Nocera1,2*, Chris Hass3
1VA Rehabilitation R & D Center of Excellence, Atlanta, USA; *Corresponding Author: joenocera@emory.edu
2Department of Neurology, Emory University, Atlanta, USA
3Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, USA
Received 20 June 2012; revised 17 July 2012; accepted 15 August 2012
Background: The Unified Parkinson’s Disease
Rating Scale is the most commonly used scale
in the clinical study of Parkinson’s disease.
However, it may fail to capture the essence of
physical impairment in patients with Parkinson’s
disease and thus limit responsiveness of care-
givers, patients, and/or clinicians as to increas-
ing physical disability. This study sought to
compare subjective measures of physical dis-
ability in Parkinson’s disease to an objective,
accurate, and proven measure of physical func-
tion-gait speed. Methods: Eighty-eight individu-
als with early to moderate stage Parkinson’s
disease were evaluated on the Unified Parkin-
son’s Disease Rating Scale, the Parkinson’s
disease Questionnaire 39 and during five 8 me-
ter walking trials. Spearman correlations coeffi-
cients were used to determine the association
among all variables of interest. Results: The
findings demonstrate th at only a fair to m od er ate
relationship between objectively measured gait
speed and physical function as measured sub-
jectively by the clinical rating scale and as
evaluated by the patients during self report.
Conclusions: The results of this study suggest
that commonly utilized measures of physical
function in Parkinson’s disease are not highly
correlated with gait speed. Because gait speed
is demonstrated as a dependable proxy for phy-
sical function, the results of this study may pro-
vide a rational for the use of gait speed to pro-
vide a more accurate picture of physical func-
on in patients with Parkinson’s disease. ti
Keywords: P arkinson’s Disease; Falls; Mobility
Disability; Gait Speed; UPDRS
Parkinson’s disease (PD) is a neurodegenerative disorder
characterized by progressive bradykin esia, rigidity, tr emo r
and postural instability. Of these four cardinal features,
perhaps none has a more debilitating impact on quality o f
life than postural instability/gait difficulty (PIGD) and
the associated mobility disability an d falls. Unfortunately,
70% to 87% of individuals with PD fall during the cou rse
of their disease [1,2]. And in fact, research demonstrates
that walking is the most common fall-related activity for
PD patients [3]. However, despite the commonality and
severe consequences of PIGD, the Unified Parkinson’s
Disease Rating Scale (UPDRS)—considered the “gold
standard” of PD clinical rating—includes only one motor
examination item specifically focused on gait (Item 29).
In addition to lack of thoroughness related to PIGD, the
UPDRS may be too simplistic and may fail to capture the
essence of PIGD given its 0 - 4 scale.
While the UPDRS is the most commonly used scale in
the clinical study of PD [4] it should be noted that re-
search demonstrates that some qualitative evaluation
measured in the UPDRS do not accurate assess the
intended outcome variable. For example, postural ins-
tability as measured subjectively by the retropulsion test
(Item 30) in the motor examination of the UPDRS is not
highly related postural instability as measured by the
more objective dynamic posturography [5]. While the rela-
tionship between balance and the UPDRS is noteworthy, a
clearer picture of the relationship between clinical gait
assessments provided by the UPDRS as well as patients
self-reports and objectively measured gait function is
needed. Understanding the relationship between the var-
ious gait assessment tools may contribute to limiting the
ambiguity in PD gait assessment. Additionally, quanti-
fying this relationship may provide the rational for a more
stringent gait assessment needed to objectively identify
those at increased risk of mobility disability and/or falls.
Therefore this study sought to investigate the rela-
tionship between the UPDRS, patient self-reports, and a
quantitative evaluation of gait function as measured by
gait speed. Importantly, gait sp eed is related to both falls
Copyright © 2012 SciRes. Openly accessible at http://www.scirp.org/journal/apd/
J. Nocera, C. Hass / Advances in Parkinson’s Disease 1 (2012) 1-4
and mobility disability in older adults and patients with
PD [3,6]. It was hypothesized that the UPDRS, given its
lack of profundity, would fail to statically correlate with
the gait speed in PD. Further, it was hypothesized that
participants would over estimate their walking ability on
the self reports when compared to the objective, quanti-
tative measure of gait speed.
Eighty-eight individuals with early to moderate stage
idiopathic PD participated in this study (Modified Hoehn
& Yahr Stage between 1 to 2.5). These patients were re-
cruited via advertisements within the University’s Move-
ment Disorders Clinic. The diagnosis of idiopathic PD
was made by a neurologist with fellowship training in
Movement Disorders using known diagnostic criteria
(UK Brain Bank Criteria for PD). All participants were
on stable doses of dopaminergics and evaluations were
conducted while the patients were clinically “ON”, or
fully responding to their PD medications (1 to 1.5 hours
of taking their antiparkinsons medicines). At the time of
testing, none of the patients exhibited any dyskinesia,
dystonia, or other signs of involuntary movement. In-
formed written consent was obtained from all partici-
pants in according with the Institutional Review Board
2.1. Subjective Evaluation
UPDRS—For the analysis this study utilized the total
UPDRS motor score as well as individual item 29
Postural instability/gait difficulties (PIGD) sub score-
Calculated utilizing the summed total of UPDRS items
27 - 30.
Parkinson’s Disease Questionnaire-39 (PDQ-39). The
PDQ-39 measures “quality of life” in eight discrete do-
mains as measured by patient self report. For the anal ysis
item 4 (had problems walking a half mile), item 5 (had
problems walking 100 yards), and item 9 (felt frighten or
worried over falling in public) were utilized.
2.2. Objective Evaluation
Gait Speed—Gait trials were performed along an 8 m
walkway, containing a force platform surrounded by a
ten camera (180 Hz) Peak Motus 3D Optical Capture
system (Peak Performance Technologies, Inc., Centen-
nial, CO). Grou nd reaction forces were collected using a
multi-component force platform (Bertec Instruments,
Columbus, OH) mounted flush with the walkway. Forces
and moments along the 3 principal axes were sampled at
360 Hz (Peak Performance Technologies, Englewood,
CO). The cameras and force platform recordings were
time synchronized using the Peak Motus video analysis
system. Passive retro-reflective markers were placed over
landmarks in accordance with the Helen Hayes marker
Participants began each trial standing quietly in a re-
laxed position. In response to a verbal cue, the partici-
pants initiated walking and continued walking for 8 me-
ters. For each participant, one to two practice trials were
followed immediately by five data collection trials. Gait
speed was calculated and averaged across all trials.
2.3. Analysis
Data were analyzed using SPSS version 20 software.
Spearman correlations coefficients were used to deter-
mine the association among item 29 of the UPDRS as
well as the UPDRS motor score and gait speed. Addi-
tionally, gait speed was analyzed in comparison to the
PIGD sub score and items 4, 5 and 9 of PDQ-39. Lastly
the subjective measures (UPDRS and PDQ-39) were
compared. The criteria used to evaluate Spearman corre-
lation coefficients were: fair (values of 0.25 - 0.50),
moderate to good (values of 0.50 - 0.75), and excellent
(values of .75 and above) [7].
All demographic data as well as means and standard
deviations of all variab les of interest are seen in Table 1.
The findings demonstrate that there is only a fair to
moderate relationship between gait speed and physical
function as measured subjectively by the clinical rating
scale and as evaluated by the patients during self report
(Table 2).
Interestingly, the subjective measures of physical
function provided by the clinician (UPDRS) and the
subjective measures provided by the patients (PDQ-39
items 4, 5 and 9) were moderately and highly correlated
(Table 3).
Table 1. Means and standard deviations on variables of interest.
Age (yr) 69.45 ± 7.07
Disease duration (yr) 9.70 ± 4.59
Avg. age at onset 58.24 ± 8.79
UPDRS motor score 23.61 ± 6. 7 0
UPDRS Item 29-Gait 0.71 ± 0.64
PIGD score 0.79 ± 0.43
PDQ-39 (Item 4) 1.25 ± 1.31
PDQ-39 (Item 5) 0.59 ± 0.98
PDQ-39 (Item 9) 0.75 ± 0.95
Gait speed (m/s) 1.10 ± 0.24
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J. Nocera, C. Hass / Advanc es in Parkinson’s Disease 1 (2012) 1-4
Copyright © 2012 SciRes. http://www.scirp.org/journal/apd/Openly accessible at
Our findings demonstrate that there is only a fair rela-
tionship between gait as measured by item 29 of the
UPDRS and gait performance as measured by gait speed.
Similarly, motor function as measured by the overall
UPDRS motor score only fairly correlated with gait
speed. Our results did show a moderate correlation be-
tween our objective measure of gait speed and the PIGD
sub score. The subjective measures of physical function
provided by the clinician and the patients were moder-
ately and highly correlated. However, neither of these
measures was found to be highly correlated with the re-
liable and validated objective measure of gait function.
These results suggest that those with early staged PD
may overestimate their walking ability and their ability
move safely through their environment. This false sense
of security my predispose individuals with PD to put
themselves in situations of high risk for a fall event.
Equally troublesome is that clinicians may also not iden-
tify subtle gait predispositions that may place a patient at
an increased risk of a fall and/or mobility disability. As
such, the clinician may be less likely to refer and suggest
patients participant in intervention strategies aimed to
improve physical function (e.g. exe rcis e).
An integral component in the prevention of falls and
mobility disability in a high-risk group is an understand-
ing by the patient, caregiver, and provider as to the risk
Ta b l e 2 . Spearmen’s correlations with p values between object-
tive and subjective measures.
Gait Speed Correlation Criteria
Motor –0.306 (0.009) Fair
Item 29 –0.408 (0.000) Fair
PIGD Sub Score –0.581 (0.000) Moderate
PDQ-4 –0.136 (0.258) Not significant
PDQ-5 –0.145 (0.229) Not significant
PDQ-9 –0.206 (0.121) Not significant
factors. Interestingly, in the case of falls for example,
Braun demonstrated that although community dwelling
older adults recognized the risks of falling they did not
consider themselves to be susceptible to falls [8]. More
specific to PD, Sadowski and colleagues examined awar-
eness of risk factors associated with falling among a
group of community dwelling adults with PD using the
Falls Risk Awareness Questionnaire [9]. Surprisingly,
this cohort recognized their increased probab ility of a fall,
however, were unaware of specific risk factors that may
increase the chances of a fall (e.g. medication use).
Pickering and colleagues evaluated the relationship
between fall rates and increased UPDRS scores hypothe-
sizing that as disease severity increased so would fall
episodes [10]. Interestingly, fall episodes did increase as
disease severity increased to a plateau for UPDRS values
of about 50. However, there was a slight decline in risk
of falling observed among cases thereafter. The most
logical explanation is that patients beyond this threshold
were immobile as a result of overt mobility disability.
However, an alternative or concurrent suggestion may be
that until this threshold is reached, clinicians, caretakers,
and perhaps patients themselves fail to recognize in-
crease fall risk and therefore fail implement a fall prevent
plan. As such, prior to an obvious increase in fall risk
deemed by disease severity, no fall prevention plan or
intervention strategies are executed. Interestingly, the
Pickering study also demonstrated that UPDRS items of
posture, gait, balance, and rising from a chair were not
independently associated with falls. The group added that
a possible explanation could be, “current clinical tests for
balance and gait are imperfect predictors of falls in eve-
ryday life [10].”
Importantly, the PIGD sub score of the UPDRS
(summed items 27 - 30) did exhibit the highest (moderate
correlation) to our objective measure of gait speed. This
sub score seeks to further describe patients’ postural sta-
bility, gait and the collective relationship to balance dif-
ficulty. The PIGD score has been utilized to give a more
comprehensive clinical evaluation of postural stability
and gait function in PD [11]. Importantly, the PIGD score
Table 3. Spearmen’s correlations with p values between subjective measures.
UPDRS Motor Item 29 PIGD Sub ScorePDQ-39 (Item-4)PDQ-39 (Item-5) PDQ-39 (Item-9)
Motor - 0.408 (0.000) 0.698 (000) 0.145 (0.229) 0.136 (0.258) 0.287 (0.015)
Item 29 0.408 (0.000) - 0.657 (0.000) 0.306 (0.009) 0.281 (0.018) 0.392 (0.001)
PIGD Sub Score 0.698 (000) 0.657 (0.000) - 0.0217 (0.070) 0.206 (0.085) 0.362 (0.002)
PDQ-4 0.145 (0.229) 0.306 (0.009) 0.0217 (0.070) - 0.702 (0.000) 0.485 (0.000)
PDQ-5 0.136 (0.258) 0.281 (0.018) 0.206 (0.085) 0.702 ( 0.000) - 0.470 (0.000)
PDQ-9 0.287 (0.015) 0.392 (0.001) 0.362 (0.002) 0.485 (0.000) 0.470 (0.000) -
J. Nocera, C. Hass / Advances in Parkinson’s Disease 1 (2012) 1-4
has been shown to correlate with the Activities-Specific
Balance Confidence scale (the ABC scale, a patient-rated
questionnaire assessing balance confidence during ac-
tivities of daily living, including walking) [11]. As such,
in conjunction with our findings, although not com-
pletely inclusive, this sub score may be viewed as a more
compressive measure of physical function in PD.
Although clinically the u se of motion analysis may not
be practical, there are more “clinic-friendly” assessments
that can provide a more robust examination of gait and
physical function. For example, we have previously
demonstrated that both the Functional Reach and the
Six-Minute walk tests correlated with dynamic postural
stability in patients with PD [12]. As such, more easily
obtainable patient information, from a stopwatch for
example, may be a valuable option for clinicians to pro-
vide informative assessments.
In conclusion, our findings suggest that subjective
measures of the UPDRS may not adequately evaluate
physical function when compared to an objective meas-
ure of gait speed. As such, the ability of the UPDRS and
patient self report may not adequately identify those that
may be at risk for a falls and/or mobility disability. While
the PIGD sub score of the UPDRS did moderately corre-
late with our objective measure of gait speed, the results
of this study suggest that a quantitative measure may
provide a more accurate picture of physical function in
patients with PD. Future research is needed to more de-
finitively identify gait speeds at which PD patients are at
risk for falls and mobility disability.
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