Can Dry Mouth Signal Early Parkinson’s Disease?

When we think of Parkinson’s disease, the image that comes to mind is someone with trembling hands, shuffling feet, or slowed movements.

But what if one of the earliest signs of Parkinson’s wasn’t visible at all?

What if it started... with your saliva?

It may sound strange, but recent research points to something fascinating!

A dry mouth or reduced saliva production (hyposialorrhea),could be one of the earliest signs of Parkinson’s disease (PD), long before the more recognizable motor symptoms show up!

Why Look Inside the Mouth for a Brain Disorder?

Parkinson’s is known as a neurodegenerative movement disorder.

But it also affects the autonomic nervous system—the system responsible for regulating automatic body functions like digestion, heart rate, and… yes, saliva production.

Saliva is secreted by salivary glands under the control of both sympathetic and parasympathetic nervous systems.

When these are disrupted by early neurodegeneration, the effect may show up in the mouth before the brain shows it in motion.

What the Research Reveals: Saliva as a Window to the Brain

1. Saliva Flow in Early-Stage Parkinson’s

In a pivotal study of 20 patients with early-stage PD (Hoehn–Yahr stage I–II), researchers measured both:

• Basal salivary flow (at rest)

• Stimulated salivary flow (after citric acid exposure)

The results were clear:

These patients were not yet on any Parkinson’s medication. That means their reduced saliva wasn’t a drug side effect—it was a direct result of early autonomic dysfunction.

2. Medications and Saliva Modulation

Another larger study involving 46 PD patients examined their salivary flow in both the “off” (no meds) and “on” (post-levodopa) states. Here’s what they found:

• Levodopa increased both basal and stimulated salivary flow, confirming that the brain plays a key role in this function.

• Domperidone, a peripheral dopamine blocker, did not inhibit this effect, further pointing to a central nervous system mechanism.

• PD patients also had elevated salivary sodium, chloride, and amylase, showing not just reduced volume but also altered composition of saliva.

What This Means in Practice

Dry mouth is usually blamed on dehydration, age, or medication. But in some cases, it might be your nervous system sending an early SOS.

For Clinicians and Dentists:

• Be alert to persistent dry mouth complaints, especially in older adults with no clear cause.

• Consider saliva flow testing as part of early neurological screening.

• Collaborate across specialities

Dentists may be the first line of detection in neurodegenerative disease.

For Researchers and Innovators:

• Saliva is being explored as a non-invasive diagnostic fluid, potentially holding molecular biomarkers like alpha-synuclein (a key protein involved in PD).

• Future saliva tests may help in early detection, monitoring progression, and even personalizing therapy.

Let’s Not Ignore the Mouth

Hyposialorrhea is not only uncomfortable; it affects chewing, swallowing, speaking, taste, and oral hygiene.

It raises the risk of cavities, fungal infections, and poor nutrition.

And now we know: It may also be an early flag for Parkinson’s disease!

“We spend so much time watching hands shake, but we forget to listen when the mouth goes quiet.”

The next time someone complains of a dry mouth—especially if it’s unexplained—it might not just be about thirst. It might be time to look a little deeper.

Inspired by:

Cersósimo MG, Tumilasci OR, Raina GB, Benarroch EE, Cardoso EM, Micheli F, Pazo JH. Hyposialorrhea as an early manifestation of Parkinson disease. Auton Neurosci. 2009 Oct 5;150(1-2):150-1. doi: 10.1016/j.autneu.2009.04.004. Epub 2009 May 5. PMID: 19419908.

Tumilasci OR, Cersósimo MG, Belforte JE, Micheli FE, Benarroch EE, Pazo JH. Quantitative study of salivary secretion in Parkinson's disease. Mov Disord. 2006 May;21(5):660-7. doi: 10.1002/mds.20784. PMID: 16419045.