Physical activity may lower the risk of developing Parkinson’s disease, a new study shows.

Parkinson’s disease occurs when certain nerve cells in an area of the brain (substantia nigra) die or become impaired. These cells produce a chemical known as dopamine, which helps direct and control muscle movement.

Parkinson’s cause has not been identified. While no cure currently exists, treatment including drug therapy and/or surgery can manage symptoms, which include tremors, stiff muscles and achiness, and problems with balance, posture, and movement.

The average age at which it is diagnosed is 60. However, about 10-20 percent of those diagnosed with Parkinson's disease are under age 50, and about half of those are diagnosed before age 40. When the diagnosis is made early, it is referred to as "young-onset" Parkinson's disease.

The new study appears in the journal Neurology’s Feb. 22 issue. It’s the work of researchers including Alberto Ascherio, MD, DrPH, associate professor of nutrition and epidemiology at the Harvard School of Public Health in Boston.

Participants included more than 48,500 male health professionals and more than 77,000 female registered nurses. At the study’s start in 1986, the men were 40-75 years old and the women were aged 40-65 years.

Starting in 1986, participants filled out questionnaires about their physical activity every two years. They reported how much time they spent per week walking or hiking outdoors; jogging; running; bicycling; swimming laps; doing calisthenics, aerobics, or aerobic dance; using a rowing machine; or playing tennis, squash, or racquetball. They also estimated the number of flights of stairs they climbed per day.

By 2000, a total of 252 men and 135 women developed Parkinson’s disease. Men were about 69 years old and women were nearly 65 when symptoms were first noticed.

Physically active men had a lower risk of Parkinson’s disease. “In men, overall physical activity was inversely associated with Parkinson’s disease risk,” write the researchers.

How Do Results Differ for Men and Women?

Strenuous activity, but not moderate activity, was the key. “A 50 percent risk reduction was observed when comparing men in the highest category of vigorous physical activity vs. those in the lowest [category],” write the researchers.

Moderate activities included walking, hiking outdoors, and stair climbing. The remaining activities were defined as vigorous.

For men, the benefit traced back to early adulthood.

“In men, levels of strenuous physical activity in high school, college, and ages 30 to 40 predicted the risk of Parkinson’s disease in later life,” write the researchers.

Men who engaged in strenuous activities for at least 10 months per year during those periods had a 60 percent lower risk of Parkinson’s disease than men who spent no more than two months per year in such activities, write the researchers.

Activity wasn’t found to have the same protective effect for women. “Neither total nor vigorous physical activity was inversely associated with Parkinson’s disease risk in women,” write the researchers.

The researchers say that more research is needed to look at why gender differences exist in exercise's protective effect against Parkinson's disease.

Activity Drops Before Diagnosis

Both men and women began to become less physically active several years before being diagnosed with Parkinson’s disease, say the researchers.

They found that men who developed Parkinson’s disease already had significantly lower levels of physical activity 12 years before diagnosis. Women became less active two to four years before diagnosis, but the trend slowed down two years after diagnosis.

The prediagnosis decline in activity may be due to changes that “may limit the patient’s capability to tolerate vigorous exercises,” say the researchers. They say other large studies are needed to confirm their findings and further explore the topic.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Chen, H. Neurology, Feb. 22, 2005, vol 64: pp 664-669. WebMD Medical Reference from Healthwise: “Parkinson’s Disease: Topic Overview.” WebMD Medical Reference from Healthwise: “Parkinson’s Disease: Symptoms.” WebMD Medical Reference from Healthwise: “Treatment Overview.” News release, Harvard School of Public Health.