- Link found in large study – the first of its kind – of 800,000 people in Denmark
- Lithium reduces risk of the disease – but only at certain concentrations
- Higher levels decreased chances but medium concentrations raised risk
- Lithium could be added to public water supplies like fluoride is to protect teeth
- Experts say lithium plays a role in dementia but further research is needed
People with higher levels of lithium in their drinking water have a lower risk of developing dementia, new research suggests.
Lithium – currently used as a drug to treat bipolar disorder – is a natural metal also found in tap water, although the amount varies from area to area.
The findings could mean it could be added to drinking water to protect our brains in the same way that fluoride is to protect our teeth, say the researchers.
The study, based on an analysis of 800,000 people in Denmark, is the first of its kind to make the link.
The researchers, writing in the journal JAMA Psychiatry, said: ‘This is the first study, to our knowledge, to investigate the association between lithium in drinking water and the incidence of dementia.
‘Higher long-term lithium exposure from drinking water may be associated with a lower incidence of dementia.’
A team from the University of Copenhagen tested water samples from 151 waterworks in Denmark.
Then then looked at the medical records of more than 73,000 Danish people with dementia and more than 733,000 without the disease and calculated their levels of lithium exposure.
The results were not entirely clear-cut. The highest concentrations of the metal were linked with a decreased risk, but medium levels brought a higher risk than lower ones.
Compared with people whose drinking water contained low levels (two to five micrograms of lithium per litre), those who consumed moderate amounts (between 5.1 and 10 micrograms per litre) were 22 per cent more likely to have dementia.
Meanwhile, those who had high levels (15 micrograms per litre or more) were 17 per cent less likely to have the condition.
Expert verdict: The jury is still out
An expert has said the findings are interesting but warn there is not yet enough evidence that adding lithium to our public water supplies would be a good idea.
David Smith, a professor emeritus of pharmacology at Oxford University, said: ‘This is a high-quality study in a large population. The association between the levels of lithium in drinking water and a diagnosis of dementia was significant, however, it was not a linear relationship.
‘Thus, the study does not have any public health implications: we should not be adding lithium salts to our tap water because we would not know what amount to use.’
He said the research was consistent with human MRI studies that show lithium salts increases the volume of parts of the brain that are involved in Alzheimer’s disease.
But he also pointed out that another element, calcium, in the water may have an effect.
‘Similar findings of a non-linear relationship have been reported for calcium in drinking water in a Chinese study.
‘It is a pity the authors did not look at the association with calcium since this might have been a confounder,’ he added.
The Alzheimer’s Society said in theory lithium might work as a treatment for Alzheimer’s disease, but further research is needed.
Dr James Pickett, head of research, said: ‘Lithium triggers a number of useful responses in brain cells.
‘However, despite some success in animals, there hasn’t been enough positive research of lithium in people with dementia to yet convince us that it works.
‘More research including clinical trials are needed, and until then we should not consider increasing lithium in drinking water.
‘In high doses, or even at low doses in some people, lithium can be toxic so it is important that people consult with their doctor before they consider taking it as a supplement.’