May 25, 2018
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Groundwater lithium exposure not linked to bipolar disorder, dementia

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Researchers found no significant link between groundwater lithium exposure and risk for bipolar disorder or dementia after adjusting for county-level demographics and health care resources, according to a research letter published in JAMA Psychiatry.

“In the United States, lithium exposure has ... been associated with lower rates of mental health disorders,” William F. Parker, MD, department of medicine, University of Chicago, and colleagues wrote. “However, mental health diagnosis rates vary substantially with local health care resources and demographics, potentially confounding the relationship with groundwater lithium concentrations.”

Parker and colleagues assessed the relationship between groundwater lithium and diagnoses of dementia and bipolar disorder in the U.S. using data from claims databases and information on groundwater lithium concentrations collected by the U.S. Geological Survey. They adjusted for county-level demographics and health care resources.

The investigators used a mixed-effects Poisson regression model, defining treatment as lithium exposure exceeding 40 g/L, to determine prevalence of bipolar disorder and dementia. They repeated this analysis for three control outcomes that have no previously reported link to groundwater lithium: major depressive disorder, myocardial infarction and prostate cancer.

Analysis showed high lithium did not confer any significant benefit for bipolar disorder, dementia or any of the controls after adjusting for demographics and health care resources at the county-level.

Researchers analyzed claims data from 4,227,556 adults living in 174 counties, where the mean and median lithium concentrations were 27.4 g/L and 11.1 g/L, respectively. Among the adults, 404,662 (9.6%) lived in one of 32 counties with lithium exposure exceeding 40 g/L. The results revealed significantly lower unadjusted prevalence rates for all outcomes in high-lithium counties; however, these areas had fewer physicians and health care resources as well as smaller, less educated and more Hispanic populations.

“We found no significant association between groundwater lithium exposure and risk of bipolar disorder or dementia after adjustment for county-level demographics and health care resource,” the authors wrote. “This indicates the purported association of high-lithium concentrations in drinking water with mental health disorders is driven by unaccounted variation in demographics, health care resources and diagnosis practices.” – by Savannah Demko

Disclosures: The authors report no relevant financial disclosures.