THURSDAY, May 18, 2023 (HealthDay News) -- Regular exercise has a long list of health benefits, and a new study suggests another one could be added: a lower risk of Parkinson's disease.
The study, of nearly 99,000 French women, found that those who were most physically active day to day were 25% less likely to develop Parkinson's over three decades, versus women who were more sedentary.
That does not prove that exercise, per se, is responsible, the researchers said. At the same time, they say it's unlikely that the link reflects "reverse-causation" -- women in the earliest stages of Parkinson's being less likely to exercise.
That's because the study assessed the women's exercise habits for up to 20 years before their Parkinson's diagnosis.
And since regular exercise clearly has benefits anyway, the findings could be seen as another motivator to get moving, said senior researcher Dr. Alexis Elbaz.
"Physical activity has beneficial effects on many body systems, including the bones, heart and lungs," said Elbaz, a research professor at the French national research institute INSERM in Paris. "And our findings show that physical activity might also contribute to preventing or delaying Parkinson's disease."
Parkinson's disease affects nearly 1 million people in the United States, according to the Parkinson's Foundation.
It is a brain disease that gradually destroys or disables cells that produce dopamine, a chemical that helps regulate movement and emotional responses.
The most visible symptoms of Parkinson's are movement-related -- tremors, stiff limbs and coordination problems -- but the effects are wide-ranging and can include depression, irritability and trouble with memory and thinking skills.
In general, researchers believe the disease arises from a complex interaction between genetic susceptibility and environmental factors.
But only a handful of modifiable risk factors have been linked to Parkinson's -- including a history of head trauma and job exposure to pesticides or heavy metals. If exercise is protective, that would make it one of the few ways to help prevent the disease.
"This is important because it represents a possible prevention strategy for a disease that has no cure and has a severe impact on quality of life," Elbaz said.
The findings -- published May 17 in the journal Neurology -- are based on just under 99,000 French women who entered a national health study in 1990. At the outset and then every few years, they answered questionnaires on their lifestyle habits and medical history.
That included questions gauging vigorous exercise, such as playing sports and running, as well as daily activities like walking, climbing stairs and household chores. The researchers gave each activity a score called a metabolic equivalent (MET), then multiplied each activity's MET by its frequency and duration.
In other words, it was a complicated measure.
Because of that, Elbaz said, it's not clear whether any particular types of exercise are related to lower Parkinson's risk.
Over three decades, 1,074 study participants developed Parkinson's. The risk, researchers found, was lowest among women who'd been most physically active in the past 10 years -- even with factors like age, weight and diet taken into account.
The one-quarter of women who were most active had a 25% lower risk of Parkinson's compared to the one-quarter who were least active.
The problem is that Parkinson's typically has a long "prodromal" phase -- a period when people may have certain symptoms, but the disease has not yet fully manifested. So it's possible that some women in that phase of the illness curtailed their activities.
To account for that, the researchers looked back at the participants' exercise habits for up to 20 years before any Parkinson's diagnosis. They found that exercise was still tied to a lower risk, though the strength of the connection was less.
There is reason to believe exercise could be protective, Elbaz said. Other research has shown, for example, that exercise can help shield brain cells from the ravages of oxidative stress -- one of the mechanisms involved in Parkinson's.
Dr. Michael Okun, national medical adviser to the nonprofit Parkinson's Foundation, called the findings "significant and important."
He noted that a handful of past studies have tied exercise to lower Parkinson's risk in men only. (Men have a higher rate of Parkinson's than women do.)
Okun said this new, large study suggests that both men and women may want to consider "lifelong" exercise as a way to reduce Parkinson's risk.
That long-term aspect is important, Elbaz said. The women in this study were 49 years old, on average, at the outset, and it was their activity levels in the previous 10 to 20 years that mattered in their Parkinson's risk.
"So it's important to exercise early in life to be able to prevent or delay the incidence of a neurodegenerative disorder such as Parkinson's disease," Elbaz said.
The Parkinson's Foundation has more on the causes of Parkinson's disease.
SOURCES: Alexis Elbaz, MD, PhD, research professor, INSERM, Paris; Michael Okun, MD, national medical adviser, Parkinson's Foundation, Miami/New York City; Neurology, May 17, 2023, online