Should gait speed be included in the clinical evaluation of Parkinson’s disease?

doi:10.4236/apd.2012.11001

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Vol.1, No.1, 1-4 (2012) Advances in Parkinson’s Disease

doi:10.4236/apd.2012.11001

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

ABSTRACT

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

1. INTRODUCTION

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

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.

2. METHODS

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

guidelines.

2.1. Subjective Evaluation

UPDRS—For the analysis this study utilized the total

UPDRS motor score as well as individual item 29

(gait).

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

system.

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].

3. RESULTS

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

J. Nocera, C. Hass / Advanc es in Parkinson’s Disease 1 (2012) 1-4

4. DISCUSSION

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

UPDRS

Motor –0.306 (0.009) Fair

Item 29 –0.408 (0.000) Fair

PIGD Sub Score –0.581 (0.000) Moderate

PDQ-39

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)

UPDRS

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-39

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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