New research links close residential proximity to golf courses with higher odds of Parkinson’s disease, especially when water is drawn from vulnerable groundwater sources. The findings spotlight potential health risks from pesticide exposure in everyday environments.
Study: Proximity to Golf Courses and Risk of Parkinson Disease. Image Credit: Trong Nguyen / Shutterstock
In a recent study published in JAMA Network Open, researchers in the United States assessed whether proximity to a golf course increases the risk of Parkinson's disease (PD).
Pesticide exposure has been associated with a heightened risk of PD. Pesticides are often used on golf courses to maintain aesthetic standards. In the United States (US), the application of pesticides to golf courses is up to 15 times greater than in European countries. Besides, pesticides can leach into the groundwater, contaminating potable water. Notwithstanding the risks, research on PD and golf course pesticide exposure is scarce.
About the study
In the present study, researchers explored the associations between proximity to golf courses and incident PD. First, PD patients in Olmsted County were identified from 1991 to 2015 within the Rochester Epidemiology Project (REP) medical records-linkage system. A movement disorder specialist reviewed medical records of identified patients to confirm diagnosis and ascertain the motor symptom onset date.
The team identified controls from the REP study region in Wisconsin and Minnesota who were age—and sex-matched to PD cases. Information on golf course locations was acquired. The residential address two or three years before PD symptom onset was used to calculate the distance from the golf course. Data on water service areas in the REP study region were obtained and categorized into areas where tap water sources are private wells, groundwater resources, and surface water resources.
Besides, water service areas were stratified as having a golf course or not. Additionally, high-resolution groundwater vulnerability data were acquired for Minnesota, and water service areas were classified as being within a vulnerable or non-vulnerable region. Groundwater vulnerable regions were those with karst geology, coarse-textured soils, or shallow bedrock.
Further, data on municipal wells in southeastern Minnesota were obtained. Water service areas were assigned as having one or zero municipal wells on golf courses and as containing shallow or deep municipal wells. Piecewise linear splines were used to assess the associations between proximity to the golf course and PD risk. Logistic regression was applied with the distance to the nearest golf course as the exposure and PD as the outcome.
The study also accounted for several demographic and socioeconomic variables, including age, sex, race, ethnicity, median household income, rural or urban classification, and health care utilization, in their statistical models.
Importantly, the study used both linear and spline models to assess the relationship between distance to the nearest golf course and PD risk. The spline model, with a knot at three miles, allowed the researchers to capture non-linear associations. Within three miles of a golf course, the risk of PD did not significantly vary by distance, but beyond three miles, each additional mile farther from a golf course was associated with a 13% decrease in the odds of PD. The spline model provided a better fit than a simple linear model, as shown by a likelihood ratio test.
Findings
From 1991 to 2015, 450 incident PD cases were recorded in Olmstead County, with 9,000 controls matched by sex and age. After exclusions, 419 PD cases and 5,113 controls were included for analysis. The nearest golf course was at a median distance of 1.72 and 1.98 miles for PD cases and controls, respectively.
The odds of PD decreased by 9% for every one-mile increment in distance from the golf course up to 18 miles. People living farther from a golf course had lower odds of PD. Furthermore, living within one mile of a golf course increased the odds of PD by 126% compared to those living over six miles away.
Besides, a substantial dose response was observed, wherein the odds of PD increased by 198% at one to two miles, 121% at two to three miles, and 92% at three to six miles compared to living over six miles away. Further, the odds of PD were almost double that of people receiving tap water from groundwater service areas with a golf course compared to those receiving it from service areas without a golf course.
Further, people receiving tap water from water service areas with a golf course in a groundwater vulnerable region had 82% higher odds of PD than those in non-vulnerable service areas with a golf course and 92% increased odds of PD relative to those living in water service areas without a golf course. Notably, there was no association between PD risk and living in service areas with a shallow municipal well.
The study also found that the association between proximity to golf courses and PD risk was stronger in urban areas. Additionally, the authors note that exposure may occur through both contaminated groundwater used for drinking and through airborne pesticide drift, particularly in higher-density areas surrounding golf courses.
Importantly, the researchers observed that within three miles of a golf course, the risk of PD did not increase further with closer proximity, suggesting a possible "ceiling effect" at higher levels of exposure.
Conclusions
Close proximity to a golf course was associated with a higher PD risk, especially within one to three miles of a golf course. People receiving tap water from water service areas with a golf course had almost double the odds of PD compared to those receiving it from service areas without a golf course. Living in a water service area with a golf course in a groundwater vulnerable region also increased the odds of PD.
However, the authors caution that while this study shows an association, it does not prove that living near a golf course causes Parkinson’s disease. The study has several limitations, including lack of information on occupational exposures, not accounting for all other potential PD risk factors, and the use of residential address as a proxy for pesticide exposure. The study population was predominantly White, which may limit the generalizability of the findings to other demographic groups. Additionally, the study relied on golf course location data from 2013 as a proxy for historical exposure, which may not fully capture long-term environmental risk.
Further research is needed to clarify the mechanisms of how pesticide exposure from golf courses may contribute to PD risk and to confirm these findings in more diverse populations.