Avoiding toxins, head injury key to Parkinson’s prevention, study says

Preventable risk factors linked to 1 in 3 cases in men, 1 in 4 in women

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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A roll of the dice as pictured here illustrates the risk of developing a disease.

Factors such as exposure to environmental toxins and repeated blows to the head — all of which can be reduced with prevention efforts — may account for nearly 1 in 3 cases of Parkinson’s disease among men, and 1 in 4 among women.

That’s according to a study of the neurodegenerative disease by researchers at the University of Alabama at Birmingham (UAB), who noted that “intrinsic risk factors (age, sex, and genetics) are inescapable, but environmental factors are not.” These scientists are looking at risk prevention as a means of reducing Parkinson’s prevalence.

“Parkinson’s disease is rising fast globally, and there is an unspoken assumption that there is no prevention — but there is,” Haydeh Payami, PhD, a professor at UAB’s department of neurology and in the Center for Neurodegeneration and Experimental Therapeutics, said in a university news story.

Payami, the study’s first author, added that this work “puts a number on how many cases of [Parkinson’s] could potentially be prevented if toxic chemicals were eliminated and if we made contact sports like football safer.”

The study, “Population fraction of Parkinson’s disease attributable to preventable risk factors,” was published as a brief communication in npj Parkinson’s Disease.

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Identifying risk factors could lead to better Parkinson’s prevention

It is believed that Parkinson’s is the result of a number of genetic and environmental factors working in combination. While genetic mutations alone account for about 5% of all disease cases, the other 95% appear to be triggered by environmental factors.

Thus, the researchers noted that “the most compelling weapon against the global rise in [Parkinson’s disease] is the elimination of risk factors.”

Their goal, therefore, was to identify these factors.

To do so, and to further understand the best strategy for preventive measures, the researchers determined the relative impact of risk factors on Parkinson’s burden by calculating the population attributable fraction or PAF — the percentage of disease that would be prevented if a risk factor were eliminated.

The study included data from 1,223 people, most living in the Deep South region of the U.S. Among them were 808 people with a diagnosis of Parkinson’s and 415 healthy individuals, who served as controls. The mean age at onset for the Parkinson’s patients was 59.3 years, and nearly two-thirds (63%) were men.

Constipation is a common non-motor symptom of Parkinson’s. In this study, the proportion of people with constipation was significantly higher among those with Parkinson’s than in controls (45% vs. 14%). It also was more common for the patient group to experience weight loss (27% vs. 14%) and rapid eye movement sleep behavior disorder (10% vs. 0%) — also non-motor symptoms of Parkinson’s.

After adjusting for factors such as age and a family history of the disease, the PAF for exposure to pesticides and herbicides — a known risk factor for Parkinson’s — was 23% for women and 17% for men.

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Blows to head in sports cited as key risk factor for men

In addition, in men, the adjusted PAF was 10% for repeated blows to the head and 6% for exposure to military-related chemicals. Exposure to environmental toxins and repeated blows to the head combined accounted for 30% of cases in men.

“Repeated blows to the head, which are common in collision sports and do not normally require medical care, were associated with a twofold increased risk of [Parkinson’s],” the researchers wrote. Previous studies have shown that concussions, which occur due to a strong hit to the head, could increase the risk for Parkinson’s later on in life.

Overall, “one in three cases of [Parkinson’s] in males, and one in four cases in females were attributed to modifiable risk factors and could have potentially been prevented,” the researchers wrote.

One caveat to these findings, the researchers noted, was that the study population was “older Southerners.” The team noted that none of the woman in the study had reported recurrent blows to the head due to involvement in sports or the military. “Only one female (with [Parkinson’s disease]) had been exposed to military-related chemicals,” they further noted.

One in three cases of [Parkinson’s] in males, and one in four cases in females were attributed to modifiable risk factors and could have potentially been prevented.

According to the researchers, “the PAF estimates reported here were based on a population of older adults and their past experiences that may have put them at risk. They are not necessarily predictive of the future.”

Nonetheless, the scientists called for prevention measures to be taken now to potentially reduced the number of future Parkinson’s cases.

“The PAFs for the future will change, for the better or worse, depending on the actions we take now to clean our environment and improve health and safety standards,” the researchers concluded.