“It could also help us more effectively identify people with early or suspected disease or people at high risk for developing the disease in the future,” says researcher Robert Abbott of the University of Virginia, Charlottesville.

Abbott and his team followed 6,790 men living on the island of Oahu, Hawaii, for 24 years. They found that men who reported persistent constipation (defined as having an average of less than one bowel movement per day) were 2.7 times more likely to develop Parkinson’s than men with an average of one bowel movement per day, and 4.5 times more likely to develop the disease than men with more than two bowel movements per day.

Adjustments to the data for dietary and environmental factors, including age, smoking, coffee consumption, laxative use, jogging and intake of fruits, vegetables and grains, did not alter the team’s findings.

Laxative-resistant

Parkinson’s disease is associated with the progressive loss of dopamine-producing cells in the substantia nigra, a part of the brain that controls movement.

“The same processes that cause the motor symptoms of Parkinson’s may also affect the colon’s functioning,” Abbott says. “There may also be some abnormalities in the muscles involved in bowel movements.”

Further research is now needed to determine whether constipation is related to the development of the disease itself, or whether it is a disease marker linked to other genetic or environmental factors that make someone more susceptible to developing the disease.

Abbott points out that constipation alone does not put a person at high risk of developing Parkinson’s. “But if people have constipation that does not respond to use of laxatives along with other factors, such as a family history of the disease, they may be at higher risk,” he says.

Journal reference: Neurology (vol 57, p456-462)