Parkinson’s disease can affect people of any sex or gender. However, male biological sex is a risk factor for Parkinson’s, with the relative risk of developing the condition being about 1.5 times greater in men than women. There are also sex differences in symptom presentation.

The reasons for sex-related disparities in Parkinson’s rates and presentation are currently not well understood. However, research points to both biological and environmental factors that may help explain why men have greater susceptibility to develop Parkinson’s compared to women.

Parkinson’s Risk Factors

The cause of Parkinson’s disease is unknown. Biological sex and environmental factors are both believed to contribute to the sex difference in the risk of developing the disease.

Risk Associated With Biological Sex

There is evidence that estrogen may have protective effects against the development of Parkinson’s disease. Estrogen is a female sex hormone that also acts as a signaling molecule within the brain. A signaling molecule sends information between cells. While all people naturally produce and use estrogen, women tend to have higher levels of estrogen than men. These higher levels of estrogen may offer some protection and contribute to the lower risk of Parkinson’s.

Higher lifetime estrogen exposure has been linked to reduced probability of developing Parkinson’s. Also, observational studies show that while women overall are less likely to develop Parkinson’s compared to men, the incidence of Parkinson’s in post-menopausal women is about the same as in men. This may be due to the reduced estrogen levels in this group.

Parkinson’s disease is characterized by the death of dopamine neurons within an area of the brain called the substantia nigra. These neurons are crucial for motor control, and their death underlies the loss of muscle control in people with Parkinson’s. Estrogens are well known to enhance the brain’s ability to produce dopamine and use it as a signaling molecule. This enhancement of dopamine signaling may counteract the development of Parkinson’s symptoms.

Estrogen may also help protect against Parkinson’s by preventing dopamine neuron death.

In rodent models of Parkinson’s, researchers have administered a drug that kills dopamine neurons in the substantia nigra to mimic Parkinson’s symptoms. Administration of estrogen protects dopamine neurons from this drug-induced cell death. The protective effect of estrogens on dopamine neurons within the substantia nigra may also contribute to the reduced risk of Parkinson’s in women.

Risk Associated With Environmental Factors

Lifetime exposure to heavy metals or certain pesticides has been linked to increased risk of developing Parkinson’s. Some types of jobs — like farming, woodworking, or metalworking — can lead to more exposure to these materials. People who work these jobs, therefore, may be at a higher risk for Parkinson’s. Some suggest that the higher prevalence of men working in these occupations may contribute to the greater risk of Parkinson’s disease in men compared to women.

Head trauma has also been linked to increased risk for Parkinson’s disease. A higher incidence of head injuries in men compared to women may also contribute to increased Parkinson’s risk.

Biological Sex Differences in Symptom Presentation

There is a large amount of variability in how people develop Parkinson’s. Men and women on average tend to exhibit different symptoms of Parkinson’s, with different levels of severity. Some studies report that women are more likely than men to exhibit the following nonmotor symptoms:

• Fatigue
• Restless legs
• Depression
• Weight change
• Constipation
• Loss of taste or smell
• Pain
• Excessive sweating

Men with Parkinson’s disease are more likely than women to present with impairments in cognition. These impairments could include deficits in attention and working memory, as well as changes in impulse control.

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