Study Detects Parkinson’s Symptoms Years Before Diagnosis

- Dec 09 2014

A new study based on the medical records of more than 8,000 people with Parkinson’s disease (PD) from the United Kingdom reports that, compared with healthy individuals, people with PD were more likely to experience symptoms such as tremor and constipation as many as ten years before their diagnosis. The results appear in the November 27 online edition of The Lancet Neurology. 

Doctors diagnose PD based on movement symptoms. But by the time difficulties such as tremor or rigidity become troublesome, more than half of the brain’s dopamine neurons that help control movement, may be lost. Much research is devoted to discovering therapies to slow or stop this brain cell death, and such neuroprotective therapies are most likely to be effective if given as early as possible.  

Knowing that symptoms like depression can appear before movement difficulties develop, researchers led by Anette Schrag, M.D., at University College London, looked for early PD symptoms in the medical records of more than 50,000 people in the United Kingdom. They identified 8,166 individuals diagnosed with PD at age 50 or more, between 1996 and 2012, and analyzed the symptoms recorded by their primary care physicians beginning ten years before the PD diagnosis. The researchers then compared the records with those of 46,755 healthy individuals of similar age and background. 

Results

• Ten years before a diagnosis of Parkinson’s, the incidence of tremor and constipation was more than double in those who went on to develop PD than in those who did not.
• Five years before diagnosis, people who later would develop PD, complained of more tremor, balance problems, constipation, low blood pressure, erectile dysfunction, urinary problems, dizziness, fatigue, depression and anxiety than those who did not develop PD.
• Two years before diagnosis, these people also had more rigidity and memory problems than those who did not develop PD.

What Does It Mean?

This study is the largest ever to chart the first occurrence of a large number of PD symptoms, prior to diagnosis, in a consistent group of people over time. The results support the current scientific understanding that PD affects movement, the digestive system, and other bodily functions well before a diagnosis is made by a neurologist.   

The major limitation of the study is that the participants were not necessarily examined by a neurologist when they first reported tremor, gait difficulty or change in memory, so it is unclear whether diagnosis could have been made earlier. Also, participants were not examined by the researchers conducting this study, so PD diagnosis is based on their medical records only. It is also important to note that while those who complained of nonmotor symptoms — constipation, low blood pressure, erectile dysfunction, urinary problems, dizziness, fatigue, depression and anxiety — were more likely to develop PD than those who did not complain, most of those who complained did not develop PD. 

However, this study and others can eventually lead to a way of screening for a wide range of symptoms, to identify those at risk for PD earlier on. Also, the results could eventually help scientists looking to develop neuroprotective therapies, which need to be tested in early-stage PD. With a better understanding of how common the early symptoms of PD are, researchers may be able to identify clinicaltrial participants at risk for PD who may be more likely to benefit from neuroprotective treatments. But first, more research is needed.  This study was not able to combine the frequencies of several symptoms together to help develop a reliable tool to predict early PD.

Commenting on the study, Anthony E. Lang, M.D., of the University of Toronto, points out that Parkinson’s remains notoriously difficult to diagnose. There is no definitive blood test, scan or other “biomarker,” and indeed, some people included in this study may have had an incorrect diagnosis. Ultimately, the study makes a valuable contribution to understanding early PD symptoms, while underscoring the need for reliable means of diagnosing the disease.

Reference: Schrag A, Horsfall L, Walters K, Noyce A, Petersen I (2014) Prediagnostic Presentations of Parkinson’s Disease in Primary Care: A Case-Control Study. The Lancet Neurology DOI: 10.1016/S1474-4422(14)70287-X

Published online November 27, 2014 

The full text is available for free at: http://dx.doi.org/10.1016/S1474-4422(14)70287-X