There is no significant association between exposure to high levels of groundwater lithium and risk for dementia or bipolar disorder in the United States after adjusting for demographic and health care resources, according to a research letter published in JAMA Psychiatry.
Previous studies have found links between lithium exposure and lower rates of mental health diagnoses, in particular, dementia and bipolar disorder. Investigators sought to examine this possible link by comparing the concentrations of lithium groundwater found by the US Geological Survey of over 3000 drinking wells to that area’s diagnoses of mental health disorders.
These diagnoses were identified from claim files from Medicaid Analytic eXtract, Truven Health MarketScan Medicare Supplemental database, and Truven Health MarketScan Commercial Claims and Encounters. Claims data were analyzed for 4,227,556 adults in 174 different counties, 404,662 (9.6%) of which lived in one of the 32 counties with high lithium exposure from the groundwater.
Primary outcomes were rates of dementia and bipolar disorder. However, to adjust for confounders and prevent spurious inferences, analyses were also conducted for 3 negative control outcomes without any known association to lithium exposure: prostate cancer, myocardial infarction, and major depressive disorder.
To adjust for county-level demographics and health care resources that would affect mental health diagnoses, data were collected from the Area Health Resources Files from the Health Resources & Services Administration.
After initial analyses, unadjusted rates showed significantly lower prevalence for all outcomes, including controls, but after adjustment for county health care resources and demographics, exposure to high lithium in groundwater showed no significant link to any of the outcomes.
Investigators conclude that “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.”
Parker WF, Gorges RJ, Gao YN, Zhang Y, Hur K, Gibbons RD. Association between groundwater lithium and the diagnosis of bipolar disorder and dementia in the United States [published online May 23, 2018]. JAMA Psychiatry. doi: 10.1001/jamapsychiatry.2018.1020