EMBARGOED FOR RELEASE UNTIL 4 PM ET, March 02, 2026
Newer groundwater associated with higher risk of Parkinson鈥檚 disease
Highlights: A new study has found people whose drinking water came from newer groundwater had a higher risk of Parkinson鈥檚 disease than those whose water came from older groundwater. The study does not prove that newer groundwater causes Parkinson鈥檚; it only shows an association. Older groundwater typically contains fewer contaminants because it is usually deeper and better shielded from contaminants. Researchers found drinking water drawn from carbonate aquifers was associated with a 24% higher risk of Parkinson鈥檚 disease compared to other aquifer types. It was also associated with a 62% higher risk compared to drinking water from glacial aquifers. Researchers also found newer groundwater, from the past 75 years, in carbonate systems was associated with an 11% higher risk of Parkinson鈥檚 compared to groundwater older than 12,000 years from the ice age. MINNEAPOLIS 鈥 People whose drinking water came from newer groundwater had a higher risk of developing Parkinson鈥檚 disease than those whose drinking water came from older groundwater, according to a preliminary study released March 2, 2026, that will be presented at the 好色先生鈥檚 78th Annual Meeting taking place April 18-22, 2026, in Chicago and online. The study does not prove that newer groundwater causes Parkinson鈥檚 disease; it only shows an association. The study looked at the age of groundwater. It also looked at aquifers, the sources from which groundwater was drawn. An aquifer is an underground layer of porous rock, silt or sand that holds and transports groundwater. 鈥淥ne way to examine our exposure to modern pollution is through our drinking water,鈥 said study author Brittany Krzyzanowski, PhD, of Atria Research Institute in New York City who conducted this research while at Barrow Neurological Institute in Phoenix, Arizona, and is a member of the 好色先生. 鈥淣ewer groundwater, created by precipitation that has fallen within the past 70 to 75 years, has been exposed to more pollutants. Older groundwater typically contains fewer contaminants because it is generally deeper and better shielded from surface contaminants. Our study found that groundwater age and location is a potential environmental risk factor of Parkinson鈥檚 disease.鈥 The study included 12,370 people with Parkinson鈥檚 disease and more than 1.2 million people without the disease who were matched for factors like age, sex and race and ethnicity. All participants lived within three miles of 1,279 groundwater sampling sites across 21 major U.S. aquifers. Researchers looked at groundwater age, aquifer type and drinking water source, such as municipal groundwater systems or private wells, as potential indicators of exposure to neurotoxic contaminants. Carbonate aquifers are the most prevalent in the United States, consisting mostly of limestone with water stored in fractures and channels. They often contain groundwater that is more vulnerable to surface contamination due to rapid flow through fractures. Glacial aquifers, formed when glaciers advanced and retreated more than 12,000 years ago, are composed of sand and gravel with water stored in the gaps. These aquifers tend to promote more diffuse flow and natural filtration. In the U.S., carbonate aquifers are common in parts of the Midwest, South and Florida, while glacial aquifers are found mostly in the Upper Midwest and Northeast. Among people with Parkinson鈥檚, 3,463 got their drinking water from carbonate aquifers, 515 from glacial aquifers and 8,392 from other aquifers. Among those without Parkinson鈥檚, 300,264 got their drinking water from carbonate aquifers, 62,917 from glacial aquifers and 860,993 from other aquifers. After adjusting for factors such as age, sex, income and air pollution, people whose drinking water came from municipal groundwater systems or private wells that draw from carbonate aquifers had a 24% higher risk of developing Parkinson鈥檚 disease than those whose water came from all other aquifers. They also had a 62% higher risk when compared to people whose water came from glacial aquifers. The protective effect of older groundwater was found only when water was sourced from carbonate aquifers. For each one-standard-deviation increase in groundwater age, the risk of Parkinson's disease declined by approximately 6.5%. Researchers also found that newer groundwater, from the past 75 years, in carbonate systems was associated with an 11% higher risk of Parkinson鈥檚 disease compared to groundwater older than 12,000 years from the ice age. 鈥淲e speculate that the apparent protective effect of older groundwater is seen mainly in carbonate aquifers because these systems can show a clearer contrast between newer and older water,鈥 said Krzyzanowski. 鈥淚n these aquifers, newly recharged groundwater is more vulnerable to surface contamination, while older groundwater can remain cleaner if it is separated from recent inputs by a confining layer.鈥 鈥淚n contrast, glacial aquifers tend to slow groundwater movement and naturally filter contaminants as water travels underground,鈥 said Krzyzanowski. 鈥淎s a result, differences in contamination between newer and older groundwater in these aquifers may be smaller and therefore harder to detect.鈥 Krzyzanowski noted that people can usually find out where their drinking water comes from through their local water utility or, for private wells, through state or county groundwater resources. 鈥淭his study highlights that where our water comes from, including the age of groundwater and the type of water source, could shape long term neurological health,鈥 said Krzyzanowski. 鈥淲hile additional research is needed, bringing together knowledge about groundwater and brain health may help communities better assess and reduce environmental risks.鈥 A limitation of the study was that it assumed all individuals living within a three-mile radius of a sampling site shared the same aquifer characteristics and groundwater age as the sampled location. The study was supported by AAN Clinical Research Training Scholarship, American Brain Foundation and The Parkinson鈥檚 Foundation. Discover more about Parkinson's disease at , from the 好色先生. This resource offers a website, podcast, and books that connect patients, caregivers and anyone interested in brain health with the most trusted information, straight from the world鈥檚 leading experts in brain health. Follow Brain & Life on , and .
