February 22, 2005 - Men who exercise regularly and vigorously can cut their risk of developing Parkinson's disease by half, according to a new study.
The research, published in the medical journal Neurology, found that men who made a habit of exercising in early adulthood and continued to do so over the years were significantly less likely to develop Parkinson's later in life.
Those who began an exercise regime later in life also benefited, but only if they embraced more demanding sports like running, cycling and squash, the researchers found.
"These are intriguing and promising findings that suggest that physical activity may contribute to the prevention of Parkinson's," said Dr. Alberto Ascherio, an associate professor of nutrition and epidemiology at the Harvard School of Public Health in Boston.
He said the mechanism involved is not entirely clear, but studies conducted on laboratory animals suggest that exercise stimulates production of key proteins that are important for the survival of neurons.
Parkinson's disease is a neurodegenerative illness that usually strikes people after age 50. It is characterized by tremors, stiffness, slowness of movement, and difficulty with balance.
Symptoms occur when neurons die in a part of the brain called the substantia nigra. Normally, these cells produce a chemical known as dopamine. Dopamine allows smooth, co-ordinated function of the body's muscles and movement. When approximately 80 per cent of the dopamine-producing cells are damaged, the symptoms of Parkinson's disease appear.
The new research was derived from two long-running health studies, the Health Professionals Follow-Up Study and the Nurses' Health Study, which include data from 48,000 male health professionals and 77,000 female nurses.
Among other things, participants filled in detailed questionnaires about the time spent on physical activity, including specific questions on walking, hiking, running, racquet sports and aerobics.
During the course of the study, 1986 to 2000, 387 cases of Parkinson's disease were diagnosed, involving 252 men and 135 women. The average age of diagnosis was 70 for men and 65 for women.
Researchers found a clear link between a long-term commitment to strenuous exercise and a lowered risk of Parkinson's disease in men, but there was no such link for women in the study.
Dr. Ascherio said this could be due to gender differences, or it may be explained by statistical anomalies. For example, there were fewer women with Parkinson's among the study participants, although the disease tends to strike men and women equally. Far fewer women than men in the study reported engaging in strenuous exercise, which also makes it more difficult to judge the association.
The researchers also noted that the long-term, strenuous exercisers were far less likely to be smokers, drank less coffee (but more alcohol), and were leaner than people who were largely sedentary. While this may affect the results, the research tried to adjust statistically for these factors.
A number of effective medicines help to ease the symptoms of Parkinson's disease, but there is no cure.