Ongoing research on Parkinson’s is revealing several risk factors related to our lifestyles and environment, some of which are actionable. Photo / 123RF
Research on Parkinson’s is revealing several risk factors related to our lifestyles and environment – and you can act on some of them.
Parkinson’s disease, once considered relatively rare, is now one of the most common neurological disorders in the world, and the second most common after Alzheimer’s disease. The number of people living with Parkinson’s has more than doubled in the past 25 years to 8.5 million, and is predicted to hit 25.2m by 2050.
The hallmark symptoms of Parkinson’s - such as tremors, stiffness, and difficulty with balance and coordination - result from the deterioration of neurons in the basal ganglia, an area of the brain that controls movement. While 10 to 15% of cases are linked to inherited genetic mutations, the rest are considered “sporadic”, with no known cause.
Although treatments are available that can manage symptoms, there is no cure or therapy that can slow disease progression. But ongoing research on Parkinson’s is revealing several risk factors related to our lifestyles and environment, some of which are actionable.
For example, moderate to vigorous exercise may reduce one’s risk, according to a 2018 meta-analysis, and some studies have shown that healthy diets focused on whole, unprocessed foods might help. Last year, a study found that higher levels of exposure to air pollution were associated with an increased risk of Parkinson’s.
Here are some lesser-known risk factors that also can be offset by actions you can take, as recommended by experts.
Caffeine lovers, rejoice! Both coffee and tea consumption have been linked to a lower risk of developing Parkinson’s disease, at least in part because of their caffeine content.
The mechanism isn’t entirely understood, but it is known that caffeine reduces oxidative stress - an imbalance of free radicals and antioxidants in the body that leads to cell damage - as well as inflammation within the brain.
A 2010 meta-analysis of 26 studies confirmed that higher caffeine intake is associated with a lower Parkinson’s risk. The association has been observed for coffee, tea and other sources of caffeine such as cola and chocolate - but notably, not for decaffeinated coffee.
“Studies show a very consistent association of a protective effect of coffee and tea drinking, whether in America, Europe or Asia,” similar to the effect from exercise, said Eng-King Tan, a professor of medicine at the Duke-NUS Medical School in Singapore. “The risk reduction generally is 25 to 30% if you take two to three 6-to-8-ounce [177-237ml) cups of coffee or tea per day over 10 years.”
A 2023 study by Tan and his colleagues found that individuals who have a genetic predisposition for Parkinson’s can significantly reduce their future risk by drinking coffee or tea.
Trichloroethylene (TCE), an industrial solvent long used in dry-cleaning, degreasing and furniture care, is considered a carcinogen and has been linked to certain types of cancer, as well as to damage to reproductive organs, the nervous system and the immune system. And a growing body of evidence is beginning to reveal that exposure to high levels of TCE such as in contaminated drinking water - as well as a closely related chemical called perchloroethylene (PCE) - may increase the risk of Parkinson’s.
In December of last year, the US Environmental Protection Agency banned most uses of PCE and TCE, although manufacturers had up to a year to comply with the rule and up to 10 years for the use of PCE in dry-cleaning and spot cleaning. However, in September, the EPA amended the prohibition compliance date for the disposal of TCE to wastewater by industrial and commercial users to begin on December 18, 2026, instead of September 15 of this year.
A groundbreaking 2023 study discovered that veterans who had been exposed to TCE- and PCE-contaminated water at Marine Corps Base Camp Lejeune in North Carolina had a 70% higher risk of developing Parkinson’s compared with veterans who resided at Camp Pendleton, a large California base that did not have contaminated water. Out of nearly 85,000 Marine Corps and Navy personnel, 279 had developed Parkinson’s at Camp Lejeune, compared with 151 out of more than 73,000 veterans at Camp Pendleton. Wells that provided water to the base from 1953 to 1987 were contaminated by leaking underground storage tanks, industrial spills, waste disposal sites and an off-base dry-cleaning business.
In the 1950s, TCE was replaced by PCE in dry-cleaning, but PCE can still biodegrade into TCE. Ray Dorsey, a professor of neurology at the University of Rochester and the author of The Parkinson’s Plan, recommends finding a dry cleaner that does not use PCE, also called “perc”. For instance, you can switch to a dry cleaner that uses professional wet cleaning, a technique involving water and biodegradable detergents instead of harsh chemical solvents such as TCE and PCE.
“California has banned PCE, but 60 to 70% of dry cleaners in the US still use it,” he said. “If your dry cleaner is using PCE, take the bag off and air your clothes outside so the chemicals aren’t released inside where you’re breathing them in.”
Numerous studies have linked exposure to high levels of pesticides to Parkinson’s disease. A 2011 study reported that combined exposure to the pesticides ziram, maneb and paraquat in workplaces in a heavily agricultural region of California increased the risk of Parkinson’s threefold.
Switching to organic produce, which avoids certain pesticides, including the three named above, has been shown to reduce pesticide biomarkers found in urine within days. Although exposure to low levels of pesticides from occasional home use or from eating non-organic produce has not been linked to Parkinson’s disease, it’s not a bad idea to wash produce or eat organic food if you can.
“Reducing your exposure to pesticides is important,” said Jeff M. Bronstein, director of the movement disorders program at UCLA and an author of the 2011 study. “These are certain fruits and vegetables that have much more contamination - like strawberries, for example.”
Regardless of whether or not you buy organic or conventional produce, he said, always wash it.
Drinking water can be a source of pesticides and industrial chemicals such as TCE. For example, pesticides applied to farmlands, gardens and lawns can seep into groundwater or surface water systems that feed drinking water supplies. A 2002 study that sampled untreated groundwater from 1255 domestic drinking-water wells and 242 public supply wells in the United States found that 44% of them contained industrial solvents and other volatile organic compounds, and 38% contained pesticides.
Golf courses are often treated with pesticides to maintain the pristine look of greens and fairways, and those chemicals can contaminate both the surrounding air and drinking water. Dorsey and his colleagues found in a study this year that people living within a mile (1.6km) of a golf course were more than twice as likely to be diagnosed with Parkinson’s compared with those living six or more miles away. Residents of a public water district with one or more golf courses had almost double the odds of developing Parkinson’s compared with those without a course.
Another study, from 2009, showed that consuming water from private wells located in areas with documented historical pesticide use resulted in an approximately 70 to 90% increase in the relative risk of Parkinson’s.
Dorsey suggests using a water filter to decrease your exposure, which can be installed for the whole house at the point of entry, or at the point of use, such as taps or a water pitcher. Research has demonstrated that home water filters with activated carbon and reverse osmosis are highly efficient for pesticide removal.
“Parkinson’s is a preventable disease. It’s not a natural consequence of aging. Eighty-seven per cent of Americans have no known genetic cause,” Dorsey said. “The origins of the disease reside outside of us. They reside in chemicals that we’re breathing in or chemicals that we’re ingesting.”