High, long-term lithium exposure from drinking water in Denmark may be associated, in a non-linear fashion, with a lower incidence of dementia, as reported in JAMA Psychiatry.
A total of 73,731 patients with dementia and 733,653 controls nationwide in Denmark were studied. The median age was 80.3 years; interquartile range was 74.9 to 84.6 years. There were 44,760 females (60.7%) and 28,971 males (39.3%).
The researchers found that patients with a diagnosis of dementia had a significantly different lithium exposure than controls: median 11.5 μg/L; interquartile range 6.5 to14.9 μg/L vs median 12.2 μg/L; interquartile range 7.3 to 16.0 μg/L; P <.001.
The incidence rate ratio (IRR) of dementia was decreased among those exposed to more than 15.0 μg/L (IRR 0/83; 95% CI 0.81-0.85; P <.001). It was increased for people with 5.1 to 10.0 μg/L (IRR 1.22; 95% CI 1.19-1.25; P <.001). The researchers discovered similar patterns with Alzheimer disease and vascular dementia as outcomes.
The researchers point out that their study was a nationwide, population-based, nested case-control study that accounted for whether individuals moved from one municipality to another. However, there might be other confounding factors associated with municipality of residence that cannot be excluded.
Dr Kessing reported working as a consultant for Lundbeck, AstraZeneca, and Sunovion. No other disclosures were reported.
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