Who Can Participate
in Clinical Trials?
Because clinical trials vary, many different types of volunteers are
needed. One thing that stays the same, though, is the consistent need for
participants both with and without Parkinson’s disease (PD). Some people
are surprised to discover that family members of people with PD, as well
as people who have no connection to the disease, are as important as
patients in moving research forward.
People Who Have
Parkinson’s
There is no one type of Parkinson’s.
Each person experiences his or her
own version of the disease. That’s why
clinical trials need people across the
spectrum of PD, with varied motor and
non-motor symptoms. Every single
person aids researchers’ efforts to
capture a fuller picture of disease and to
develop targeted treatments.
associated with Parkinson’s are
more common in people of certain
backgrounds, such as those of Ashkenazi
Jewish descent and North African
Berbers. When studying these mutations
and therapies, it makes sense to start by
looking at people from these populations
and their families.
People Who Do Not
Have Parkinson’s
In interventional trials, researchers seek
volunteers representative of the people
who will ultimately use the therapy
outside of trials: women and men of
varied ages, races and ethnicities.
Clinical studies require a wide range
of participants because — aside from
the uniqueness of Parkinson’s —
we’re all individuals who may have
different responses to therapies.
When investigators include diverse
populations, they can be sure their
intervention will be safe and effective in
a broad group of people with PD. Study participants who do not have PD
provide essential information in clinical
research. Often referred to as “control”
volunteers, these individuals can
contribute to both interventional
and observational trials. In Phase I
trials, they test new therapies for
safety. In observational studies, they
can help researchers define “non-
Parkinson’s disease” measurements
and be a bar against which natural
changes in Parkinson’s are compared.
When researchers match control and
patient volunteers on age, gender and
other characteristics, they can evaluate
whether differences on surveys or exams
(e.g., blood tests, brain scans or memory
scales) are due to Parkinson’s.
In some cases, researchers may seek
out specific subsets of people with PD.
For example, some genetic mutations Another area control volunteers,
especially those who have a family
member with PD, can contribute is
Remember fact 1:
Patients Are Key Research Partners.
through genetic research. Studies might
compare genes of family members with
and without PD to identify which may
be associated with the disease. Or, they
may look to first-degree relatives who
carry PD-associated genetic mutations
for insights on disease causes, risk factors
and potential protective factors. (See
“Chapter 3: Genetics and Parkinson’s
Research,” pg. 29.)
Different Trials Need
Different Volunteers
Because trials look at different aspects
of Park inson’s, each needs specific types
of volunteer. At the outset, researchers
establish guidelines — known as
inclusion and exclusion criteria — for
who can and can’t participate. Qualified
volunteers must (or must not) possess
the outlined characteristics, which
can include age, gender, symptoms,
disease stage, medication, other medical
conditions or genetic factors. This
checklist isn’t meant to keep people out
of trials, but rather to get the right people
into the right trials and keep researchers
on track toward the answers they need.
It’s also intended to minimize risks.
People taking medications that could
interact with the study medication, for
example, often are excluded.
Chapter 1 — Clinical Research Basics
11