Parkinson’s disease is a progressive neurodegenerative disorder that primarily affects movement. It develops gradually, often starting with a barely noticeable tremor in one limb, and can also lead to stiffness, slowed movement, and impaired balance. The exact cause of Parkinson’s disease remains unknown, but it is understood that a combination of various factors contributes to its development.
Age
Advancing age is the most significant factor associated with developing Parkinson’s disease. While the condition can manifest at any age, the likelihood of diagnosis increases considerably after 60 years old. The average age of onset is around 60, though it can occur earlier, with about 4% of diagnoses happening before age 50.
The brain’s substantia nigra, a region responsible for producing dopamine, experiences a natural loss of cells as people age. This process typically occurs slowly, but in individuals who develop Parkinson’s, the cell loss accelerates, leading to symptoms once 50% to 60% of these cells are gone.
Genetic Predisposition
Genetics play a role in Parkinson’s disease, though they account for a smaller percentage of cases compared to those without a clear genetic link, often referred to as sporadic Parkinson’s. Familial Parkinson’s occurs when multiple family members are affected, indicating a stronger genetic component. Even in sporadic cases, certain genetic variations can increase an individual’s susceptibility.
Mutations in the LRRK2 gene are considered the most common genetic cause, appearing in both familial and sporadic cases. The GBA gene, which codes for a lysosomal enzyme, and the SNCA gene, responsible for producing the alpha-synuclein protein, are also associated with increased risk. These mutations do not guarantee that a person will develop Parkinson’s, as some individuals with the mutation may never show symptoms.
Environmental Exposures
Environmental factors are increasingly recognized as contributors to Parkinson’s disease risk. Exposure to certain pesticides and herbicides has been consistently linked to an elevated risk. For instance, insecticides like rotenone and permethrin, and herbicides such as paraquat and 2,4-dichlorophenoxyacetic acid (2,4-D), have been implicated.
Industrial chemicals also pose a potential risk. Trichloroethylene (TCE), a solvent used in various industrial settings, has shown an association with long-term exposure and Parkinson’s development. Heavy metals, including high-dose manganese exposure in occupations like welding, are known to cause a form of parkinsonism, and lead exposure may also increase risk. While these connections are observed, they are often correlational, suggesting an increased risk rather than a definitive sole cause.
Prolonged exposure to well water may also be a concern due to potential contaminants. Research indicates that environmental toxins can induce inflammation, mitochondrial damage, and oxidative stress, which are processes linked to the death of dopamine-producing cells in the brain.
Head Trauma and Demographic Factors
A history of head trauma, particularly repeated injuries, has been associated with an increased risk of Parkinson’s disease. Studies suggest severe head injuries leading to loss of consciousness may increase risk. The association is more pronounced for head injuries occurring earlier in life.
Demographic factors also show some variations in Parkinson’s risk. Men are about 1.5 times more likely to be affected by Parkinson’s disease than women. Research on racial and ethnic differences indicates that white and Hispanic populations in the United States may have higher rates of Parkinson’s disease compared to Black and Asian populations, though ongoing studies are often limited by specific geographic populations.