MONDAY, Aug. 13, 2001 (HealthDayNews) -- Doctors know that 80 percent of patients diagnosed with Parkinson's Disease suffer from constipation. Even James Parkinson noticed the link between constipation and the disease that would bear his name.
Now a new study suggests that men with constipation have at least twice the risk of developing Parkinson's.
The findings, reported in the Aug. 14 issue of Neurology, offer the first evidence that constipation can predate this neurological disorder by many years. Constipation, defined as less than one bowel movement a day, affects roughly 5 percent of the general population.
Parkinson's disease (PD) is a central nervous system disorder that affects up to 1 million Americans. While the cause of PD is not known, researchers suspect that a genetic predisposition and an as-yet-unknown environmental factor trigger the disease.
Robert Abbott, a professor of biostatistics and statistics at the University of Virginia School of Medicine and the director of biostatistics at the Pacific Health Research Institute in Honolulu, led the study.
Using data from the Honolulu Heart Program, which followed 6,790 men aged 51 to 74 on the island of Oahu for 24 years, the researchers found 96 who developed PD.
After ruling out the effects of age, smoking, coffee consumption, laxative use and diet, Abbott found that men with constipation were 2.7 times more likely to develop PD than men who averaged one bowel movement a day.
Compared with men who had two bowel movements a day, constipated men were 4.1 times more likely to develop PD and 4.5 times more likely than men who averaged more than two bowel movements a day.
"The same processes that cause the motor symptoms of PD may also affect the colon's functioning," says Abbott. "PD does not just involve the brain but could also involve other systems.
The fact that constipation can predate PD is exciting to us because it could mean that the pathology of PD might be recognizable before the usual motor [symptoms] that we most often think about in the patient with PD. Unfortunately, we can't say why the pathology in the gastrointestinal tract might appear before the motor symptoms."
Abbott speculates that constipation could be a marker of greater susceptibility to PD, but perhaps only if an unknown environmental trigger is present. "The bottom line? You might need both susceptibility and the environmental factor to make PD risk a real problem."
The researchers suspect that with other signs of PD, such as a family history and early motor disorders, constipation could help identify individuals at high risk for PD.
"Early identification could increase the capacity to enroll subjects into neuroclinical trials that might lead to new therapies or the identification of risk factors," says Abbott. "Once these therapies and risk factors have been identified, then early diagnosis might be important for the optimization of intervention and prevention effects."
However, the clinical applications of the findings are not yet clear. "Perhaps constipation in someone who is not finding relief from medications, who also has a family history of PD and emerging motor [symptoms], needs closer follow-up from a neurologist, " says Abbott. "But again, such recommendations are hard to make, particularly since constipation becomes increasingly common in the elderly."
Dr. Robert Friedland, chief of neurogeriatrics at the Case Western Reserve University in Cleveland, Ohio, calls the findings "very impressive."
"It's possible that the neurodegeneration affects the nervous system in the intestine," says Friedland. However, he says, "It's also possible that this is related to some environmental exposure which has two effects: One is that you are at a higher risk of getting PD, and the other is that you are constipated."
The researchers say the findings shouldn't alarm the average person struggling with constipation. "Even in those with constipation, the risk of PD low. In one year, PD would be expected to occur in fewer than 20 per 10,000 people," says Abbott. "Although this rate is still much higher than when constipation is absent, it is still a relatively uncommon event."
"The important finding in our report is not to create concern about constipation, but rather to help researchers understand how PD progresses. Again, our data suggest that the pathology in PD does not just involve the brain but could also involve other systems."
In patients with the PD, an area of their brain called the substantia nigra produces far too little of a neurotransmitter called dopamine, which normally allows for smooth muscular movement. The symptoms of the disease, which is somewhat more common in men that in women, include progressive rigidity, tremor, slowness of movement and difficulty walking.
While PD has no cure, patients can choose between several drug and surgical therapies that target the symptoms of the disorder.
What To Do
For more information on PD, check the Parkinson's Disease Foundation, the National Institute of Neurological Disorders and Stroke or the Michael J. Fox Foundation for Parkinson's Research.
Meanwhile, the National Institute of Diabetes and Digestive and Kidney Diseases has a primer on constipation.
