While the exact cause of Parkinson’s disease (PD) remains unknown, researchers believe it is caused by a combination of genetic and environmental factors. Environmental factors include anything a person comes into contact with, their upbringing, and where they live. Research into the environmental factors that may play a role in the development of PD has focused on several areas.
Exposure to pesticides is associated with an increased risk of developing PD. Organochlorine insecticides, such as DDT, are most commonly associated with PD. Although most of these pesticides were banned 30-40 years ago, their chemical structures resist breakdown, and they can stay in the environment for a long time.1
Research has also identified that use of the pesticides rotenone and paraquat can increase a person’s risk of developing PD 2.5 times more than non-users. Other pesticides that have been associated with PD include permethrin and 2,4-dichlorophenoxyacetic acid (2,4-D). Exposure to pesticides can occur in home use, such as in hobby gardening, or in larger quantities in people who use pesticides as part of their work, such as in farming. However, most people who are exposed to these pesticides do not develop PD, and additional research is needed to understand which people exposed to which pesticides are most at risk.1,2
Many studies have looked at the effects of diet on the risk of developing PD, both to understand what increases a person’s risk as well as what may decrease their risk of developing the disease. Studies have focused on fats (polyunsaturated versus saturated), Vitamin D, phytochemicals from vegetables and fruits, and reduced calorie diets. Some studies have found people have a reduced risk when eating a Mediterranean-style diet, which is high in vegetables, whole grains, fruits, and legumes along with moderately high levels of fish, but low to moderate levels of dairy, meat, and poultry. Other studies have looked at the protective effect associated with higher intakes of flavonoids (found in tea, berries, apples, oranges, and red wine).1,3-5
Research has found that engaging in regular exercise may provide protection against developing PD. One study found that individuals who consistently engaged in physical activity at high levels had a 51% lower risk of PD than those with low levels of activity. Also, participation in competitive sports before age 25 was also associated with a lower incidence of PD.1,6
Trauma to the head, neck, or upper cervical spine seems to increase a person’s risk of developing PD. While the research is not conclusive, several studies have shown a link between head trauma and Parkinson’s leading doctors to believe that injury to the head may increase a person’s risk of developing the disease.7
Some research studies have found an increased risk for PD with certain occupations, although research findings are inconsistent. A higher risk of developing PD has been associated with agricultural and industrial workers, and a lower risk of developing PD has been associated with shift work and jobs that involve physical exertion. It is not clear if the higher risk of PD with agricultural and industrial jobs is due to exposure to chemicals, including pesticides, metals, and polychlorinated biphenyls (PCBs). Additional research is needed.2
Most of the research in air pollution has focused on heart and lung diseases; however, researchers are beginning to explore the role air pollution may have on neurodegenerative diseases like PD.1