NEW YORK - RESULTS of a study suggest an association between erectile dysfunction and an increased risk of developing Parkinson's disease.

The autonomic nervous system, which regulates involuntary bodily functions like heart rate and digestion, is often affected in Parkinson's disease, and erectile function, which is controlled by the autonomic system, is commonly compromised, the study team notes in a report.

'An important question,' according to Dr Xiang Gao, of Harvard School of Public Health, Boston, Massachusetts, and colleagues, 'is whether erectile dysfunction precedes the onset of motor symptoms of Parkinson's disease.'

They examined the question using data from the Health Professionals Follow-up Study. A total of 32,616 men free of Parkinson's disease in 1986 were included in the present study.

In 2000, the men completed a questionnaire with questions on erectile dysfunction in different time periods. The relation between erectile dysfunction before 1986 and Parkinson's disease risk from 1986 to 2002 was analyzed.

During the 16 years' follow-up, 200 men were diagnosed with Parkinson's disease.

Compared to men who reported very good erectile function before 1986, those who reported erectile dysfunction had a significant 3.8-fold increased risk of developing Parkinson's disease, the investigators report.

'We further explored possible interactions of erectile function with age, body mass index, cigarette smoking, caffeine intake, and the presence of diabetes during follow-up,' Dr Xiang's team explains. 'None of these interactions was significant.'

These findings, they conclude, support the hypothesis that the autonomic nervous system 'may have been impaired years before Parkinson's disease is clinically recognisable'. -- REUTERS