Parkinson's disease: four symptoms that can appear decades before diagnosis

Certain non-motor signs — loss of smell, acting out dreams, chronic constipation and dizziness on standing — can appear years or even decades before a Parkinson's disease diagnosis.

Researchers and clinicians note that several non-motor signs often appear long before Parkinson's disease is diagnosed. A resting tremor is not required for diagnosis, and up to 20 percent of people with Parkinson's do not have one. Symptoms such as loss of smell, REM sleep behavior disorder, chronic constipation and orthostatic hypotension can precede movement changes by years or decades. Scientists are studying these prodromal markers to better understand how the disease begins and progresses. Key early features: - Loss of sense of smell: More than 90 percent of people with Parkinson's gradually lose their sense of smell, and this can begin up to about 20 years before diagnosis; those with reduced smell have been reported to have about a fivefold increased risk of developing Parkinson's. - Acting out dreams (REM sleep behavior disorder): Studies report that 50 to 70 percent of people with this sleep disorder will develop Parkinson's disease or a related condition within an average of five to 10 years, and people 50 and older with the disorder have a much higher likelihood compared with those without it; registries and research consortia track these cases for study. - Constipation: Chronic constipation affects roughly two-thirds of people with Parkinson's; a meta-analysis found people with constipation were about twice as likely to develop Parkinson's compared with those without, and long-term studies have linked infrequent bowel movements decades earlier with higher risk. - Dizziness when standing (orthostatic hypotension): A drop in blood pressure on standing can have many causes, but when unexplained and neurological in origin it has been associated with later development of Parkinson's or related conditions in some studies, though the evidence is less strong than for other markers. Summary: These prodromal markers are not individually specific enough to diagnose Parkinson's disease, and many can have other causes. Researchers aim to refine how combinations of symptoms and other markers might improve early identification, and studies and registries are ongoing. Undetermined at this time.