The Earliest Symptoms of Parkinson's Disease

Doctors use the classic motor symptoms of Parkinson’s disease — slowness of movement (bradykinesia), resting tremor and rigidity — to determine whether a patient’s symptoms are consistent with a diagnosis of Parkinson's.

But some researchers now are focusing on a new groups of symptoms — so-called "pre-motor symptoms" that can predate the three classic signs of Parkinson's by several years.

Studies have shown that the process of dopamine loss has been going on for at least five years prior to the development of motor symptoms in Parkinson's disease, so it would be possible to have very early symptoms related to the disease.

Of course, many of these pre-motor symptoms are not very specific and are relatively common in people who don't go on to have Parkinson's. Therefore, not everyone who develops Parkinson’s displays these pre-motor symptoms, and not everyone who experiences these symptoms goes on to develop Parkinson’s.

What are considered to be pre-motor symptoms of Parkinson’s? Doctors still haven't nailed down the complete list, but the following symptoms are generally considered to be included:

Olfactory Dysfunction

Although difficulty smelling may seem like a rather trivial issue, it is actually pretty important. Approximately 60% to 100% of Parkinson’s patients who already have motor symptoms have olfactory dysfunction.

In fact, one study found this symptom was the most accurate predictive factor that a person would develop Parkinson's. A huge clinical trial showed that individuals with low olfactory functioning had a 5.2-fold increase in developing Parkinson’s and that impaired smell can precede motor symptoms by at least four years.

Constipation

Constipation has long been associated with the motor symptoms of Parkinson’s. But it also seems that constipation may actually also be a pre-motor symptom of this disease. One study showed that people who experienced constipation in mid-life had a four-fold risk of developing Parkinson’s later in life.

REM Sleep Behavior Disorder

People who have this disorder play out their dreams while asleep by vocalizing, grabbing, kicking and punching. Their dream activities are often violent and can injure either the patient or the patient's bed partner.

This disorder is the most consistent pre-motor predictor of Parkinson’s. Studies have shown a significant correlation, including one demonstrating that 45% of people with RBD had developed either Parkinson’s or Lewy body dementia by 11-and-a-half years later.

Depression

​This is a debatable symptom to include in the pre-motor group since there isn't strong evidence linking depression to Parkinson's. However, studies that look at the history of Parkinson’s patients often see an increase in the percentage of these individuals with depression when compared to controls.

What does this mean? It means that people with Parkinson’s are more likely to have a history of depression compared to the general population. However, most patients with depression don’t go on to develop Parkinson’s. 

Why is it important to know about pre-motor symptoms of Parkinson's disease? Well, there are several reasons.

First of all, recognizing these early manifestations of Parkinson’s increases our understanding of the course of the disease, as well as the process that causes it. And although no treatments exist that will cure Parkinson's right now, one can speculate that when these are developed, they could be used to treat the disease at its earliest stages — before the motor symptoms start.