Summary: Could the water you drink affect your brain? A large preliminary study finds a clear association between the age and type of groundwater people use for drinking and their risk of Parkinson’s disease.
Researchers report that people whose drinking water comes from relatively “new” groundwater—recharged within roughly the last 70–75 years—or from certain underground reservoirs called carbonate aquifers experienced a higher risk of developing Parkinson’s disease. The results point toward the possibility that surface-level contaminants, which more readily reach modern, shallow water supplies, may influence neurological health across the United States.
Key facts
- Groundwater age: Water recharged within the past 70–75 years was linked to a higher Parkinson’s risk compared with older groundwater. Deep glacial aquifers (water older than about 12,000 years) were associated with the lowest risk.
- Carbonate aquifers: Drinking water sourced from carbonate aquifers—common in parts of the Midwest, the South and Florida—was associated with a 24% higher risk of Parkinson’s disease compared with water from other aquifer types.
- Comparison to glacial systems: In carbonate systems, newer groundwater showed an 11% higher risk than ice‑age–old groundwater.
- Why age matters: Older groundwater tends to be deeper and better shielded from surface pollution, while carbonate aquifers can allow rapid flow and therefore faster transport of surface contaminants.
- Study scale: The analysis included more than 1.2 million people across 21 major U.S. aquifers, including 12,370 individuals with Parkinson’s disease.
Source: AAN
Overview of the findings
A preliminary study, scheduled for presentation at the American Academy of Neurology’s 78th Annual Meeting (April 18–22, 2026), found that people who obtain drinking water from newer groundwater supplies had a higher chance of being diagnosed with Parkinson’s disease than those whose water came from older groundwater. The study demonstrates an association but does not establish a direct cause-and-effect relationship.
Lead author Brittany Krzyzanowski, PhD, of Atria Research Institute in New York City (who conducted the work while at Barrow Neurological Institute in Phoenix, Arizona) explained the idea behind the study: “One way to examine our exposure to modern pollution is through our drinking water. Newer 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’s disease.”
The research team analyzed groundwater age, aquifer type and drinking water source—municipal groundwater systems versus private wells—as proxies for exposure to neurotoxic contaminants in the environment. An aquifer is an underground layer of porous rock, sand or gravel that stores and transmits groundwater.
Carbonate aquifers, made primarily of limestone, store water in fractures and channels and are widespread across the U.S. These systems can allow rapid groundwater flow, increasing vulnerability to contamination from the surface. By contrast, glacial aquifers—formed by sand and gravel deposited during glacier advances and retreats more than 12,000 years ago—tend to promote slower, more diffuse flow and provide greater natural filtration.
Among the study participants, 3,463 people with Parkinson’s obtained drinking water from carbonate aquifers, 515 from glacial aquifers and 8,392 from other types of aquifers. Among more than 1.2 million matched controls without Parkinson’s disease, 300,264 drank from carbonate aquifers, 62,917 from glacial aquifers and 860,993 from other aquifers.
After adjusting for potential confounders such as age, sex, income and air pollution, people whose drinking water came from municipal groundwater systems or private wells drawing from carbonate aquifers had a 24% higher risk of developing Parkinson’s disease than those whose water came from other aquifers. Compared specifically with people whose water came from glacial aquifers, the risk was 62% higher.
The protective association of older groundwater was most apparent in carbonate aquifers: for each standard-deviation increase in groundwater age, Parkinson’s risk declined by roughly 6.5%. In carbonate systems, water recharged within the last 75 years carried an 11% higher risk compared with groundwater older than 12,000 years.
Krzyzanowski suggested a reason for the pattern: “We 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. In 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. In contrast, glacial aquifers tend to slow groundwater movement and naturally filter contaminants as water travels underground, so differences between newer and older water may be smaller and harder to detect.”
She added that residents can usually learn the origin of their drinking water by contacting local water utilities or, for private wells, state or county groundwater resource offices.
The authors emphasize that further research is needed to identify specific contaminants and exposure pathways. One limitation of the current analysis is the assumption that all individuals living within a three-mile radius of a sampling site shared the same aquifer characteristics and groundwater age as the sampled location, which may not always capture local variability.
Funding: The study was supported by the AAN Clinical Research Training Scholarship, the American Brain Foundation and The Parkinson’s Foundation.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by staff.
About this Parkinson’s disease research news
Author: Renee Tessman
Source: AAN
Contact: Renee Tessman – AAN
Image: The image is credited to Neuroscience News
Original research: The findings will be presented at the American Academy of Neurology’s 78th Annual Meeting (April 18–22, 2026).