HealthDay News — Lithium in drinking water is associated with the incidence of dementia in a nonlinear pattern, according to a study published in JAMA Psychiatry.

Lars Vedel Kessing, MD, from the University of Copenhagen in Denmark, and colleagues conducted a population-based study to examine whether the incidence of dementia in the general population covaries with long-term exposure to microlevels of lithium in the drinking water. Data were included for 73,731 patients with dementia and 733,653 controls.

The researchers observed a significant difference in lithium exposure for patients with a diagnosis of dementia (median, 11.5 µg/L) and controls (median, 12.2 µg/L; P <.001). 

The association was nonlinear. The incidence rate ratio (IRR) of dementia was decreased in those exposed to more than 15.0 µg/L (IRR, 0.83; 95% CI, 0.81-0.85; P <.001) and 10.1 to 15.0 µg/L (IRR, 0.98; 95% CI, 0.96-1.01; P =.17), and increased with exposure to 5.1 to 10.0 µg/L (IRR, 1.22; 95% CI, 1.19-1.25; P <.001), compared with those exposed to 2.0 to 5.0 µg/L. With Alzheimer’s disease and vascular dementia as outcomes, the patterns were similar.

“Long-term increased lithium exposure in drinking water may be associated with a lower incidence of dementia in a nonlinear way; however, confounding from other factors associated with municipality of residence cannot be excluded,” the authors write.

Disclosures: One author disclosed financial ties to the pharmaceutical industry.

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Reference

Kessing LV, Gerds TA, Knudsen NN, et al. Association of lithium in drinking water with the incidence of dementia [published online August 23, 2017]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2017.2362