Head Trauma, Lead Exposure Tied to Parkinson’s in Regional Study

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by Forest Ray PhD |

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Head trauma causing a person to black out, and lead exposure — even through hobbies — may more than double a person’s risk of developing Parkinson’s disease, according to a study of people in the New England area.

Having a close relative with this disease was also identified as a risk factor by its researchers, but pesticide exposure was not.

The study “Lifestyle Factors and Parkinson’s Disease Risk in a Rural New England Case-Control Study” was published in the journal Parkinson’s Disease.

Parkinson’s is a complex neurological disorder involving the progressive loss of coordination and movement, as the neurons underlying those processes accumulate damage and die off.

Although Parkinson’s specific cause remains unknown, many risk factors — both genetic and environmental — are thought to contribute to a likelihood of developing it.

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The disease’s environmental risk factors include exposure to pesticides, heavy metals, and air pollutants, as well as traumatic brain injury. Pesticides, in particular, have attracted researchers’ attention as possible Parkinson’s triggers.

Given evidence supporting a link between agriculture and Parkinson’s, researchers at the Geisel School of Medicine at Dartmouth, in New Hampshire, wondered why Medicare records showed relatively high disease concentrations in both their region of the Northeast and in the Midwest. Between these two regions, agriculture and its related pesticide use is only widespread in the Midwest.

They decided to examine environmental exposures and lifestyle behaviors among people in a rural area of New England with and without Parkinson’s.

“Identifying environmental factors that increase [Parkinson’s] risk would allow exposure mitigation and disease prevention efforts while facilitating the experimental investigation of mechanisms and intervention opportunities,” they wrote.

Investigators conducted a survey of 97 people with Parkinson’s, with a mean age of 69.36, and 195 age- and sex-matched healthy individuals (a control group) in New Hampshire and neighboring Vermont between 2017 and 2020. Respondents were asked about their employment, hobbies, physical activity, exposures to various substances, and family medical histories.

Overall, head trauma involving a loss of consciousness, exposure to lead, and a family history of Parkinson’s associated with statistically significant risk of developing the disorder. Smoking history, exposure to agricultural pesticides and other chemicals, and working in farming or agriculture did not associate with a significantly higher risk in this study.

“Approximately 9–10% of respondents reported having ‘participated in farming/agriculture for at least two times each month for a year or longer,’ but this was not associated” with Parkinson’s, the study reported.

Head injuries that led to a loss of consciousness appeared as the greatest risk factor, occurring in 42.7% of Parkinson’s patients and 18.4% of controls. This amounted to a roughly four times higher Parkinson’s risk.

“The [head trauma] risk remained significantly increased in a model adjusted for age, sex, smoking, family history, and athletic activity” between patients and controls, the researchers wrote. Participation in sports and being physically active, otherwise, did not raise disease risk.

Exposure to lead associated with a 2.7 times greater Parkinson’s risk, after adjusting for these same factors (age, smoking history, family history, etc.).

Activities promoting lead exposure included ‘making stained glass or art glass using lead joints,’ ‘casting bullets or other lead objects,’ and ‘making or using lead fish weights/sinkers,’ the researchers noted.

A family history of this disease was also a risk factor, with 22.7% of patients having first- or second-degree relatives with Parkinson’s versus 6.7% of controls.

“Overall, our results from Northern New England support previous reports of head injury and lead exposure as [Parkinson’s] risk factors,” the researchers concluded.

“From a public health perspective,” they aded, “our findings and the literature encourage the use of lead substitutes and helmets [with activities], which are general health recommendations that may also reduce the risk of [Parkinson’s].”

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