Causes and risk factors of Parkinson’s disease
Most cases of Parkinson’s disease are idiopathic and the cause is unknown.
It is widely believed that people with Parkinson’s disease are genetically predisposed to the disease, and that one or more unknown factors in the environment can ultimately cause Parkinson’s disease.
Most of the symptoms of Parkinson’s disease are caused by the loss of neurons in an area of the brain called the substantia nigra.
Normally, neurons in this part of the brain produce the chemical messenger (neurotransmitter) dopamine, which allows them to communicate with another region of the brain, the striatum.
This communication helps create smooth, purposeful movement. When neurons in the substantia nigra die, the resulting loss of communication causes the motor (movement-related) symptoms of Parkinson’s disease.
The cause of this cell death is unknown, but many researchers believe that cells are killed by aggregated proteins called Lewy bodies.
What are Lewy bodies?
Affected neurons in Parkinson’s disease patients have been found to contain aggregated proteins called Lewy bodies. Researchers do not yet understand why Lewy bodies form or what role they play in the disease, but they are thought to be toxic.
Lewy bodies are clumps of a protein called alpha-synuclein. Neurons cannot break down these protein clumps, which can lead to the death of these cells.
Other theoretical causes of brain cell death in Parkinson’s patients include free radical damage, inflammation, or toxins.
What are the risk factors for Parkinson’s disease?
Risk factors for Parkinson’s disease include:
genetics
People who have a first-degree relative (parent or sibling) with Parkinson’s disease may have an increased risk of developing Parkinson’s disease, perhaps as much as 9% higher. Genetic risk factors (the presence of certain genes associated with Parkinson’s disease) are more common in early-onset Parkinson’s disease.
It is estimated that 15% to 25% of people with Parkinson’s disease have a family history of Parkinson’s disease, but a condition with known genetic links, called familial Parkinson’s disease, is relatively rare.
year
The average age of onset is 60 years, and the incidence increases with age. Approximately 5 to 10 percent of people have an “early-onset” or “young-onset” disease that begins before age 50.
sex
The prevalence of Parkinson’s disease is approximately 1.5 times higher in men than in women.
However, some recent studies suggest that sex differences may not be as pronounced as previously thought.
Exposure to pesticides
Exposure to some pesticides has been shown to increase the risk of developing Parkinson’s disease.
Problematic chemicals include organochlorine pesticides such as DDT, dieldrin, and chlordane. Rotenone and permethrin are also involved.
Proximity to golf courses where large amounts of pesticides are used in course management is associated with increased risk of Parkinson’s disease. In 2025, JAMA network open The study concluded that “the greatest risk for PD is found within 1 to 3 miles of a golf course, and the risk generally decreases with increasing distance.”
Exposure to fungicides and herbicides
Exposure to the fungicide maneb and the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), paraquat, or Agent Orange may increase the risk of Parkinson’s disease.
A 2023 study of Agent Orange exposure in Vietnam veterans found that the rate of Parkinson’s disease was 1.31 times the normal rate.
head injury
Recurrent head trauma, especially repetitive head trauma, can contribute to the development of Parkinson’s disease in some people. Traumatic brain injury is also a major risk factor for developing Parkinson’s disease later in life.
coffee and smoking
