Largest Ever Parkinson’s Study Shows How Symptoms Differ Between Men And Women

Lyndsey
Collins-Praino, Adelaide
University

Parkinson’s disease is
the fastest growing neurological disorder, with over
10 million cases worldwide. Up to 150,000
Australians currently live with the disease and 50 new cases
are diagnosed each day.

The number of people
living with Parkison’s is projected
to more than triple between 2020 and 2050.

Yet
despite the immense impact on those living with
Parkinson’s and their loved ones, and the staggering cost
to our economy – at
least A$10 billion a year – there is still a lot we
don’t know about how this disease presents and
progresses.

A recent large-scale
study of nearly 11,000 Australians living with
Parkinson’s disease provides some critical insights into
symptoms, risk factors and how these affect men and women
differently. Let’s take a look.

First, what is
Parkinson’s disease?

Parkinson’s is a progressive
disease in which cells that produce the chemical
messenger dopamine in a part of the brain called the
“substantia nigra” begin to die. This is accompanied by
multiple other brain changes.

It is usually
considered a movement disorder. Common motor symptoms
include a resting tremor, slowed movement (bradykinesia),
muscle stiffness and balance issues.

But
Parkinson’s also involves a variety of lesser known non-motor
symptoms. These may include:

• mood
  changes
• difficulties with memory and cognition
  (including slower thinking, challenges with planning or
  multitasking and difficulty paying attention or
  concentrating)
• sleep
  disturbances
• autonomic dysfunction (such as
  constipation, low blood pressure and urinary problems).

While these are sometimes referred to as
the “invisible” symptoms of Parkinson’s, they often
have a greater negative impact on quality of
life than motor symptoms.

So, what does the
new research tell us?

The study used data
collected as part of the Australian Parkinson’s Genetics
Study led by the QIMR Berghofer Medical Research Institute.
After a pilot study in 2020, it was launched as an ongoing,
nationwide research project in 2022.

Some 10,929
Australians with Parkinson’s were surveyed and provided
saliva samples for genetic analysis. This is the largest
Parkinson’s cohort studied in Australia and the largest
active cohort worldwide.

There were several key
initial findings.

1. Non-motor symptoms are
common

The study reinforced how common non-motor
symptoms are, with loss of smell (52%), changes in memory
(65%), pain (66%) and dizziness (66%) all commonly reported.

Notably, 96% of participants experienced sleep
disturbances, such as insomnia and daytime
sleepiness.

2. A better picture of risk
factors

The study also provided insights into what
can influence Parkinson’s risk.

This is
important because we don’t completely understand what
causes the dopamine producing cells in the substantia nigra
to die in the first place.

Age
is the primary risk factor for Parkinson’s. The new study
found the average age for symptom onset was 64, and for
diagnosis, 68.

3. Genes and environment both play
a role

In the recent study, one in four people
(25%) had a family history of Parkinson’s. But only 10–15%
of Parkinson’s cases are caused by – or strongly linked
to – mutations in specific genes.

It’s important to remember that families don’t
only share genes but often their
environment.

Multiple environmental
factors, such as pesticide exposure and traumatic brain
injury, also increase risk of Parkinson’s.

The
majority (85–90%) of cases of Parkinson’s are likely due
to complex
interaction between genetic and environmental risk
factors, and advancing age.

The study showed
environmental exposures linked to Parkinson’s risk were
common:

• 36% of people reported pesticide
  exposure
• 16% had a prior history of traumatic
  brain injury
• 33% had worked in high-risk
  occupations (such as agriculture, or petrochemicals or metal
  processing).

These exposures were
significantly higher in men than in women.

4.
Differences between the sexes

The disease is 1.5
times more common in men. In the new study, 63% of those
surveyed were male.

Parkinson’s also presents
and progresses differently
in males and females.

The study found women were
younger than men at time of symptom onset (63.7 versus 64.4
years) and diagnosis (67.6 versus 68.1 years), and more
likely than men to experience pain (70% versus 63%) and
falls (45% versus 41%).

Men experienced more
memory changes than women (67% versus 61%) and impulsive
behaviours, particularly sexual behaviour (56% versus 19%)
– although most participants exhibited no or only mild
impulsivity.

What we still don’t
know

The large-scale study and its comprehensive
survey shed valuable light on people living with
Parkinson’s in Australia.

But it’s still only a
sliver of the population. More than 186,000 people with
Parkinson’s were invited to participate and just under
11,000 took part – a less than 6% response rate.

Of these participants, 93% had European ancestry.
So this sample may not be fully representative of
Parkinson’s disease.

The information we have
about symptoms also relied on self-reports by the study’s
participants, which are subjective and can be biased or less
reliable than objective measurements of function. To address
this, the researchers are planning to use smartphones and
wearable devices to collect more comprehensive
data.

Finally, while this provides a snapshot of
the current cohort, it’s not clear how participants
compare to people of a similar age without Parkinson’s, or
how their symptoms may change over time.

These are
important areas of future research for this ongoing
study.

What all this means

Studies like
this provide crucial insights into risk factors linked to
Parkinson’s. They also help us better understand the
symptoms people experience.

This is important
because the way Parkinson’s presents varies from person to
person. Not everyone will experience the same symptoms to
the same extent.

Similarly, the way the disease
progresses over time differs between people.

A
better understanding of the factors that influence this can
lead to earlier identification of who’s at risk and more
personalised ways of managing this disease.

Lyndsey
Collins-Praino, Associate Professor, School of
Biomedicine, Adelaide
University

This article is
republished from The
Conversation under a Creative Commons license. Read the
original
article.