Advances in Parkinson’s Disease, 2016, 5, 87-96
ISSN Online: 2169-9720
ISSN Print: 2169-9712
DOI: 10.4236/apd.2016.54011 November 25, 2016
Racial Disparities in Parkinson Disease: A
Systematic Review of the Literature
Chantale O. Branson, Andrew Ferree, Anna D. Hohler, Marie-Helene Saint-Hilaire
Department of Neurology, Boston University School of Medicine, Boston, MA, USA
Racial differences in the prevalence of Parkinson’s disease (PD) have been reported
Many of the earliest reports were flawed because they were based on
crude datasets, such as hospital databases, death certificates, door-to-
and records of Medicare beneficiaries. These studies provided conflicting results and
were found to have numerous biases. Publications with improved study designs in
recent years have yielded higher quality findings that are worth reviewing. We r
viewed studies published between 2005 and 2014 that analyzed the racial differences
in Parkinson’s disease diagnosis, treatment—including deep brain stimulation—
access to care. Literature searches were conducted in PubMed and EBSCO. These
studies highlight advances in the field and explore differences in PD among ethnic
and racial groups. Our literature review focused on prevalence, treatment and dia
nosis discrepancies, and racial variations in the perceptions of aging. An appraisal of
lve reviewed studies determined a decrease in prevalence and incidence of PD in
Americans of African descent compared to Caucasians. The studies also showed
multiple health disparities, including lack of access to care, treatment, and inclusion
. More studies are needed to address the causes and prevention of health
disparities, as well as solutions, such as community outreach.
Racial and Ethnic Disparities, Epidemiology, Parkinson’s Disease
Parkinson’s disease (PD) is a neurodegenerative disorder that is diagnosed based on
clinical features, including bradykinesia, resting tremor, rigidity, and postural stability.
These clinical findings are essential for physicians to make an accurate diagnosis, which
subsequently will lead to improvement of clinical outcomes and quality of care. Studies
How to cite this paper:
., Hohler, A.D. and Saint-Hilaire,
.-H. (2016) Racial Disparities in Parkin-
son Disease: A Systematic Review of the Li
Advances in Parkinson’s Dis
October 27, 2016
November 21, 2016
November 25, 2016
Copyright © 201
6 by authors and
Research Publishing Inc.
This work is licensed under the Creative
Commons Attribution International
License (CC BY
C. O. Branson et al.
have suggested there is a lower prevalence of PD among African-Americans. It is un-
clear if this is due to genetics, or inequalities among access to care, diagnosis, and
In 2004, McInerney-Leo
. analyzed prevalence and incidence of PD among Afri-
can-Americans compared to Caucasians . There were six studies that analyzed the
prevalence and incidence of PD through hospital records, physician registration and
death certificates. The results were conflicting because of biased study designs, including
low power, healthcare access, physician bias and ascertainment bias. The article recom-
mended future studies conduct a long-term survey of the population to determine the
incidence and phenotype of PD among Caucasians compared to African-Americans.
Understanding the epidemiological characters of PD among minorities will help to
address the disparity in the care of this population. It will also ultimately provide a
deeper understanding of the biological, environmental, and genetic mechanisms of the
disease. Therefore, we undertook a literature review of racial disparities in PD focusing
on articles published since 2004.
We performed a database search of articles published after 2004 that studied racial dis-
parities in every facet of Parkinson’s disease among patients of African ancestry com-
pared to Caucasians. Topics included access to care, diagnosis, treatment, and inclusion
in research. A search in PubMed and Medline of literature with the following terms:
(racial disparities and Parkinson’s disease) and (racial disparities and veterans affairs)
resulted in ten studies; Two additional articles were obtained from references of the
studies elicited from PubMed and Medline. We reviewed twelve studies published be-
tween 2005 and 2014, which are found in Table 1. Many of the studies used the term
white for Caucasian and black for African-American. A summation of the studies in-
cluding the study design, study type, results, limitations and strengths are discussed
3.1. Studies at Tertiary Movement Disorders Centers
In 2011, Hemming
. assessed the racial and socioeconomic disparities (annual in-
come and educational level) via cross-sectional analysis of patients seen at a tertiary
Movement Disorders center at the University of Maryland. The authors evaluated the
prevalence of PD among patients who self-identified as African-Americans compared
to whites (93.4% white and 6.1% African-American).
The study revealed that African-Americans, at the time of diagnosis, had greater
disability, disease severity, and were prescribed fewer anti-parkinson medications than
Caucasians. Most notably, African-Americans had a two-fold increase in years between
disease onset and diagnosis . The limitations of this study included a small sample
size (66 African-Americans) and referral bias given a select population referred to a ter-
tiary center. Other confounding factors, such as socioeconomic status including income
C. O. Branson et al.
Table 1. Twelve studies analyzing the prevalence, incidence, management and treatment of PD among whites compared with non-whites.
Author & Journal
Disparities in the Recording
of PD on Death Certificates
By studying the prevalence of PD
based on death certificates the
findings showed socioeconomic
biases confounding the results.
Disparities of care in
veterans with Parkinson’s
N = 65/374 (9.35%)
Hispanic or Latino
N = 30/374 (8.02%)
N = 11/374 (2.94%)
N = 1/375 (0.27%)
6% racial/ethnic disparity of
adherence to PD quality
indicators among non-Hispanic
whites compared to non-whites
Annals of Neurology
Treatment disparities in
N = 43 (14%)
N = 264 (86%)
African-American patients did
not receive similar treatment for
PD compared to white patients.
Racial Differences in the
Diagnosis of Parkinson’s
N = 123,489 (68%)
N = 50,808 (28%)
N = 7,974 (4%)
PD diagnosis among African-
Americans was half the rate of
Geographic and Ethnic
Variation in Parkinson
Disease: A Population-Based
Study of US Medicare
N = 25,581,561 (86.6%)
N = 2,356,271 (8.0%)
N = 593,234 (2.0%)
N = 470,024 (1.6%)
N = 96,262 (0.3%)
N = 66,448 (0.2%)
N = 367,034 (1.2%)
1. The mean prevalence of PD
per 100,000 is 1.6% of the elderly
population over 65 years of age.
2. Prevalence in Blacks and Asians
was 50% lower compared to Whites.
3. Blacks have a higher PD related
morbidity than whites.
Racial Differences in Parkinson’s
Disease Medication Use in the
Reasons for Geographic and
Racial Differences in Stroke
Cohort: A Cross-Sectional Study
N = 10,123 (41.7%)
N = 14,242 (58.3%)
1. Whites more frequently used PD
medications compared with blacks.
2. The group without health insurance
was less likely to take PD medications.
Delayed Parkinson’s Disease
Diagnosis among African-Americans:
The role of reporting of disability
N = 16 (22%)
N = 58 (78%)
Newly diagnosed PD among African-
Americans were found to have a greater
motor impairment compared to whites.
Racial and Socioeconomic
N = 1090
N = 66 (6.05%)
N = 1024 (93.94%)
African-Americans were found to
have a higher disability and disease
severity compared with whites at a
tertiary Movement Disorders Center.
2012 PLOS ONE
Validation of an Instrument to
Measure Older Adults’
N = 192
N = 60 (31%)
N = 119 (62%)
N = 3 (2%)
Understanding expectations about
movement among the elderly
through development of a scale.
A randomized recruitment
intervention trial in Parkinson’s
disease to increase participant
diversity: early stopping for
lack of efficacy 
N = 1572 (90.2%)
N = 40 (2.3%)
N = 75 (4.3%)
N = 42 (2.4%)
N = 13 (0.8%)
The Ancillary Trial lacked the overall
number of participants that were
needed for true analysis and was
C. O. Branson et al.
J Cross Cult
Knowledge and Attitudes About
Parkinson’s Disease Among a
Diverse Group of Older Adults
75 total participants
Community members were found to
have a lower level of knowledge about
PD compared to PD support group
Disparities in Access to Deep
Brain Stimulation Surgery for
4.7% of all PD discharges that
were African Americans, 0.1% were
DBS related discharges.
and level of education. The authors stated racial disparities are multi-faceted, and rec-
ommend additional studies that assess the attitudes of patients and physicians regard-
ing PD, PD referral and treatment.
3.2. Studies Using Databases
. assessed racial differences in PD via a cross-sectional study, which also
identified potential environmental factors. In this study, PD cases were identified from
the United States Medicare benefit recipients with ICD-9 codes 332 or 332.0 in 1995,
and from 2000 to 2005. Benefits recipients with ICD-9 codes 332.1 (secondary Parkin-
sonism) or 333.0 (other degenerative disease of the basal ganglia) were excluded. The
sample size was 450,000 PD cases per year. Medicare denominator files included birth,
race, sex, residence, zip code, and mortality data for US Americans over the age of 65. It
did not include people who were eligible for Medicare, but were in a health mainten-
ance organization. The mean prevalence of PD was 1,588.43/100,000 among Medicare
beneficiaries over age 65. Of the Medicare recipients, the mean age-related prevalence
of PD was 1671.63/100,000 among Caucasian enrollees and 1,036.41/100,000 among
African-American enrollees. The mean annual incidence of PD for Medicare recipients
from 2002 to 2005 was 445.79/100,000 and this remained stable since 1995 .
This was a well-designed study, which was well powered due to the large sample size.
It also analyzed the prevalence and incidence of PD, which included demographic as
well as geographic factors. Willis
. confirmed that the prevalence among African-
Americans were fifty percent lower than the prevalence among Caucasians. The inci-
dence ratio among African-Americans as compared to Caucasians were higher than the
prevalence ratio, suggesting African-Americans have a greater PD-related mortality
than Caucasians. The study also reduced referral and selection bias because the cases
were obtained from a database. Geographic and demographic variables were analyzed
as well, which revealed a higher prevalence of PD in the Midwest and Northeast areas.
The regions were termed the “Parkinson disease belt.” The limitations of this study in-
cluded data collection. Obtaining Medicare files excluded patients who were less than
C. O. Branson et al.
65 years of age. Although, the incidence of PD increases with age, the mean age of onset
is 61.6 years, so patients who are not yet on Medicare were excluded . The use of
billing codes can result in false positives due to miscoding of other parkinsonian syn-
dromes as PD. The risk of false negatives may be higher among African-Americans if
there is a delay in diagnosing PD. Lack of access to care may exclude African-Americans
from obtaining Medicare.
In another study, Dahodwala
. reviewed Pennsylvania Medicaid claims from
January 1, 1999 to December 31, 2003 to evaluate treatment disparities in PD . Cases
that included a claim for secondary Parkinsonism, such as schizophrenia and bipolar
disorder were excluded. Three hundred seven new cases of PD were identified based on
the criteria of Medicaid enrollment, having one Medicaid reimbursement claim asso-
ciated with PD, and no previous claims associated with PD or Parkinsonism related
Treatment for PD included medications, physical therapy and/or a return clinic visit
for PD within six months of the initial diagnosis. Of the new cases, 86% were Caucasian
and 14% were African-American. There were no statistical differences in age, sex, initial
diagnosis, or Medicaid eligibility between the two groups. Of the 307 cases, 104 were
prescribed medication or physical therapy while 124 received a second visit. One-third
of African-Americans received PD treatment compared to Caucasians (p = 0.002).
There were no differences in the number of return clinic visits. This study highlights
the racial disparities in treatment of PD. The authors hypothesized that lack of effective
communication from providers to African-American patients with PD may have con-
tributed to the gap in quality of care. It was also unclear, if the lower rate of treatment
among African-Americans were from the providers not prescribing, or the patients not
The study was limited by selection bias, as the patients with PD who applied for Me-
dicaid were typically low income and disabled. It also lacked documentation of the
clinical reasoning or decision making that may have contributed to African-Americans
not receiving treatments, such as comorbid conditions that make treatment difficult
. The authors recommended interventions to address disparity, such as community,
patient and physician awareness, as well as developing interventions to reduce inequi-
ties in care. However, these were not discussed in detail.
. analyzed disparities of care among veterans with PD in a retrospective
study using ICD-9 code 332.0 from October 1, 2001 to September 30, 2002 followed by
further chart review of the same patients, from 1998 to 2004. Medical charts were re-
viewed by trained nurses blinded to the study hypothesis to confirm the diagnosis of
PD using ten indicator measures of PD care . Out of five hundred seventy-seven
cases with ICD-9 code 332.0, four hundred one PD cases were confirmed. Of those cas-
es, twenty-seven were excluded due to lack of information about race or ethnicity. Re-
sults showed that physicians were more likely to confirm a diagnosis of PD among
Non-Hispanic Whites than non-Whites. Physicians assessed depression equally among
non-Hispanic whites and non-Whites, but the non-Hispanic whites were more likely to
C. O. Branson et al.
start treatment and receive follow-up. Patients who were offered treatment for depres-
sion and refused were included in the initial treatment group. Many providers did not
document if they offered treatment for depression among the untreated group.
3.3. Access and Treatment Disparities
., and Chan
. highlighted several ways race affects
access to healthcare and treatment. Each of the studies revealed that even after being
diagnosed with PD, African-American patients did not receive adequate first line me-
dications, physical therapy, treatment for depression, or referral for deep brain stimula-
tion (DBS) procedure   .
African-Americans were found to have significantly fewer DBS procedures compared
to Whites (unadjusted odds ratio, 0.13; 95% confidence interval, 0.11 - 0.16; P < 0.001)
. After adjusting for comorbidities that may contraindicate DBS, African-Americans
were eight times less likely to receive DBS treatment. Despite the fact that Afri-
can-Americans were more likely to receive care from urban hospitals with a higher
number of neurologists and neurosurgeons.
The disparities in care also included treatment for Parkinson’s disease depression
(PDD). Proper treatment of depression is associated with better quality of life. Cheng
. reported that physicians did not consistently document whether PD patients who
were depressed refused either medication or mental health referral. The rates of initial
treatment (92% vs. 80%, p = 0.04), and follow-up treatment (82% vs 64%, p = 0.05) of
depression among African-Americans were lower than non-Hispanic whites, despite
there being no difference between race and ethnicity in the assessment of depression
., reported that African-Americans were four times less likely than
whites to receive any PD treatment (odds ratio, 0.24; 95% confidence interval, 0.09 -
0.64), including physical therapy. This raises concern for communication breakdown
among the providers . They also reported a difference in expectations between the
populations about normal aging.
3.4. Perceptions of Normal Aging
An interesting confounding variable regarding PD epidemiology in different popula-
tions is variation in perceptions of normal aging. Dahodwala and colleagues were the
first to examine this by comparing the stage of disease at which African-Americans and
white PD patients were first diagnosed . By comparing records from the Philadelphia
Veterans Affairs Medical Center, they determined that African-American patients in-
itially presented at more advanced stages of disease compared to their white counter-
parts (Hoehn and Yahr stage, 2.5 vs 2.0). Surprisingly, despite greater motor impair-
ment, the degree of reported disability among African-Americans was half of what
whites reported (Unified Parkinson Disease Rating Scale-disability, 40% vs 81%). This
striking discovery regarding disease perception provides a plausible, yet likely partial,
explanation for the documented discrepancies in PD prevalence between African-
C. O. Branson et al.
Americans and Caucasians.
Discrepancies in perceptions of normal motor performance with aging was explored
directly again by Dahodwala and colleagues . They generated a novel assessment tool
for testing participants’ views on Expectations Regarding Movement (ERM) with ques-
tions tailored for parkinsonian symptoms. The investigators used this questionnaire to
assess 210 senior center residents in Delaware County, Pennsylvania and demonstrated
African-Americans held significantly lower expectations for maintenance of mobility
compared to whites. However, there was no difference between the groups with respect
to expectations of aging in general. Other participant characteristics that significantly
improved ERM scores were higher education (more than high school) and better self-
reported health (very good or excellent).
Another study investigated the issue of perceptional variation in PD with a two-
pronged approach in senior communities in Philadelphia . The study first held fo-
cus groups in senior centers to obtain a qualitative understanding of differences in
knowledge and perspectives on PD amongst whites, African-Americans and Chinese-
Americans. In the quantitative arm of the study, Pan and colleagues constructed a
questionnaire based on the findings from the 75 focus group participants. The ques-
tionnaire was administered to 154 individuals and revealed commonalities and differ-
ences between the three racial groups. Two common themes shared across groups were
an overall lack of knowledge regarding the disease, and concern over losing indepen-
dence as a consequence of developing PD. Distrust of the healthcare system and lan-
guage barriers were identified as unique obstacles to treatment perceived by African-
and Chinese-Americans. Echoing previous studies, African- and Chinese-Americans
were both more likely to view parkinsonian symptoms as part of normal aging com-
pared to whites.
These three illustrative studies revealed substantial differences in both expectations
for normal aging and perceived degree of disability from parkinsonian symptoms. The
work highlights a likely contributing factor in the variance in PD prevalence amongst
different racial and ethnic groups. These studies also point to the importance and need
for outreach and education regarding PD in the senior population.
Many of the studies revealed the incidence and prevalence of PD are higher among-
Caucasians compared to African-Americans. Since the McInerny-Leo
review many of the study designs have improved. Yet, there are still limitations making
it difficult to assess the overall prevalence of PD among African-Americans compared
to Caucasians. For example, Willis
. provided the largest study to-date on PD inci-
dence and prevalence among African-American population compared to Caucasians by
using the Unites States health care database. There are several strengths within this
study, including the large sample size and serial cross-sectional study design. However,
there were a few limitations, including false positives, case clustering and under-diagnosis
due to lack of healthcare access, which may have skewed the overall prevalence of PD in
C. O. Branson et al.
the African-American population.
Studies analyzing access and treatment disparities revealed a delay in diagnosis and
treatment bias . The studies were retrospective, which evaluated ICD-9 codes.
Therefore, they could not determine if the patient refused treatment or if the physician
did not offer standard treatment making it difficult to determine the cause of these dis-
parities. There were many hypotheses, which included underreporting of symptoms,
mistrust of the medical field and lack of effective communication between the patient
and physician . African-Americans were also found to have greater disease severity
and disability compared to whites likely as a result of delay in diagnosis and treatment
. The studies that revealed a treatment bias also did not address ways to prevent this
There were two studies analyzing the misperceptions of motor performance with ag-
. analyzed expectations of normal aging via mixed-methods, which re-
vealed several barriers to attitudes and knowledge. Understanding these barriers would
improve delays in diagnosis and treatment. The study revealed African-Americans and
Chinese-Americans perceived parkinsonian symptoms as a part of normal aging.
Therefore, many of the symptoms that may seem vague to the patient become the phy-
sician’s responsibility to educate them and their care providers.
Are physicians asking the right questions to get an accurate history based on racial
and cultural differences? Additional training to the initial primary provider and out-
reach programs, such as increasing patient awareness are warranted.
., recommended future studies such as, a long-term survey of a
population with a similar proportion of Caucasians and African-Americans similar to
the door-to-door survey of Parkinson’s disease in Copiah County, Mississippi, and Ni-
geria . Dahodwala
., also analyzed racial differences in the diagnosis of Parkin-
son’s disease in a cohort study and they came to a similar conclusion. The racial differ-
ences in PD incidence were not elucidated by age, sex, income, insurance, geographic
variation or healthcare utilization. They concluded that the racial disparities were more
likely a result of discrimination or bias and a population-based approach will help de-
termine the root cause of these differences.
These studies support the need for a long population-based study to analyze the true
incidence of Parkinson’s disease and better understand how various biases can cause
under diagnosis and delay in treatment. It will also help with targeted interventions,
such as screening surveys, teaching measures to prevent under-reporting of symptoms
and under-diagnoses. Understanding the epidemiological constructs of race in PD will
allow us to have a better understanding of Parkinson’s disease and help us improve care
for an underserved population.
There were twelve studies analyzing the prevalence, incidence, management and treat-
ment of Parkinson’s disease among people of color compared with whites. The majority
of the studies used databases, such as the United States Medical benefit recipients, the
C. O. Branson et al.
Pennsylvania Medicaid claims, and death certificates and medical charts of veterans
with Parkinson’s disease     . Since the McInerney-Leo article, there has
been one cross-sectional study at a Movement Disorders center reviewing social and
socioeconomic disparities .
Studies analyzing access to care and management were retrospective chart reviews.
They found a disproportionate number of African-Americans receiving less care, in-
cluding medical treatment, physical therapy, depression management, and deep brain
stimulation. Although the studies did not analyze the causes of the disparities between
African Americans and whites, they highlighted a problem with communication and
under-reporting    .
Three studies analyzed the perception and knowledge of PD symptoms in different
populations   . These studies emphasized the differences between racial and
ethnic groups, but did not reveal the root of these perceptions.
The review articles revealed racial disparities in every facet of Parkinson’s disease,
from knowledge about the disease, to diagnosis, and finally treatment. Racial disparities
also existed within the Veterans’ Affairs health care system, which should provide an
equal standard of care to all veterans. Unfortunately, the studies do not address the
causes of these observations and further studies need to be conducted to determine ra-
cial. A community-based study has yet to be performed and may deepen our under-
standing of Parkinson’s disease.
 McInerney-Leo, A., Gwinn-Hardy, K. and Nussbaum, R.L. (2004) Prevalence of Parkinson’s
Disease in Populations of African Ancestry: A Review.
Journal of the National Medical As-
, 96, 974.
 Hemming, J.P., Gruber-Baldini, A.L., Anderson, K.E., Fishman, P.S., Reich, S.G., Weiner,
W.J. and Shulman, L.M. (2011) Racial and Socioeconomic Disparities in Parkinsonism.
Archives of Neurology
, 68, 498-503. https://doi.org/10.1001/archneurol.2010.326
 Wright Willis, A., Evanoff, B.A., Lian, M., Criswell, S.R. and Racette, B.A. (2010) Geo-
graphic and Ethnic Variation in Parkinson Disease: A Population-Based Study of US Med-
, 34, 143-151. https://doi.org/10.1159/000275491
 Pagano, G., Ferrara, N., Brooks, D.J. and Pavese, N. (2016) Age at Onset and Parkinson
, 86, 1400-1407.
 Dahodwala, N., Xie, M., Noll, E., Siderowf, A. and Mandell, D.S. (2009) Treatment Dispari-
ties in Parkinson’s Disease.
Annals of Neurology,
 Cheng, E.M., Siderowf, A.D., Swarztrauber, K., Lee, M., Vassar, S., Jacob, E., Eisa, M.S. and
Vickrey, B.G. (2008) Disparities of Care in Veterens with Parkinson’s Disease.
ism & Related Disorders
, 14, 8-14. https://doi.org/10.1016/j.parkreldis.2007.05.001
 Chan, A.K., McGovern, R.A., Brown, L.T., Sheehy, J.P., Zacharia, B.E., Mikell, C.B., Bruce,
S.S., Ford, B. and McKhann, G.M. (2014) Disparities in Access to Deep Brain Stimulation
Surgery for Parkinson Disease: Interaction between African American Race and Medicaid
, 71, 291-299. https://doi.org/10.1001/jamaneurol.2013.5798
C. O. Branson et al.
 Dahodwala, N., Karlawish, J., Siderowf, A., Duda, J.E. and Mandell, D.S. (2011) Delayed
Parkinson’s Disease Diagnosis among African-Americans: The Role of Reporting of Disa-
, 36, 150-154. https://doi.org/10.1159/000324935
 Dahodwala, N., Karlawish, J., Shea, J.A., Zubritsky, C., Stern, M. and Mandell, D.S. (2012)
Validation of an Instrument to Measure Older Adults’ Expectations Regarding Movement
, 7, Article ID: e43854. https://doi.org/10.1371/journal.pone.0043854
 Pan, S., Stutzbach, J., Reichwein, S., Lee, B.K. and Dahodwala, N. (2014) Knowledge and
Attitudes About Parkinson’s Disease Among a Diverse Group of Older Adults.
, 29, 339-352. https://doi.org/10.1007/s10823-014-9233-x
 Schoenberg, B.S., Osuntokun, B.O., Adeuja, A.O., Bademosi,O., Nottidge, V., Anderson,
D.W. and Haerer, A.F. (1988) Comparison of the Prevalence of Parkinson’s Disease in
Black Populations in the Rural United States and in Rural Nigeria Door-to-Door Commu-
, 38, 645. https://doi.org/10.1212/WNL.38.4.645
 Pressley, J.C., Tang, M.X., Marder, K., Cote, L.J. and Mayeux, R. (2005) Disparities in the
Recording of Parkinson’s Disease on Death Certificates. Movement Disorders, 20, 315-321.
 Dahodwala, N., Siderowf, A., Xie, M., Noll, E., Stern, M. and Mandell, D.S. (2009) Racial
Differences in the Diagnosis of Parkinson’s Disease.
 Yacoubian, T.A., Howard, G., Kissela, B., Sands, C.D. and Standaert, D.G. (2009) Racial
Differences in Parkinson’s Disease Medication Use in the Reasons for Geographic and Ra-
cial Differences in Stroke Cohort: A Cross-Sectional Study.
 Tilley, B.C., Mainous, A.G., Elm, J.J., Pickelsimer, E., Soderstrom, L.H., Ford, M.E., Diaz,
V.A., Siminoff, L.A., Burau, K. and Smith, D.W. (2012) A Randomized Recruitment Inter-
vention Trial in Parkinson’s Disease to Increase Participant Diversity: Early Stopping for
Lack of Efficacy.
9, 188-197. https://doi.org/10.1177/1740774512436881
Submit or recommend next manuscript to SCIRP and we will provide best service
Accepting pre-submission inquiries through Email, Facebook, LinkedIn, Twitter, etc.
A wide selection of journals (inclusive of 9 subjects, more than 200 journals)
Providing 24-hour high-quality service
User-friendly online submission system
Fair and swift peer-review system
Efficient typesetting and proofreading procedure
Display of the result of downloads and visits, as well as the number of cited articles
Maximum dissemination of your research work
Submit your manuscript at: http://papersubmission.scirp.org/
Or contact firstname.lastname@example.org