Late last year, dementia overtook heart disease as the leading cause of death in England and Wales, highlighting an urgent need to find new ways to detect the condition early and to treat it.
There are already around 47 million people worldwide living with some form of dementia – a chronic or persistent breakdown of mental processes caused by brain disease or injury and marked by symptoms including memory loss, personality change and impaired reasoning. However, that figure is predicted to rise to 131 million by 2050 as the world’s population lives longer.
There is currently no cure for dementia and much of the research being done is focussed on early detection of the condition and ways to prevent it or slow its progress. Now researchers at the University of Copenhagen, in Denmark, believe that increasing levels of lithium in drinking water could cut the risk of dementia in the general population.
Their study of 800,000 people showed that those with the highest levels of lithium in their drinking water (above 15 micrograms per litre) had a 17% reduction in risk of developing dementia. But confusingly, those with moderate levels of lithium (between5 and 10 micrograms per litre) were actually more at risk (22%) of developing dementia than those with low levels (below 5 micrograms per litre).
Lithium is found naturally in tap water, but the levels vary according to where you live, which allowed the Danish research team to carry out its large-scale study. It concluded that people with long-term exposure to higher levels of lithium in their drinking water could be at significantly less risk of developing dementia. However, the researchers accept that other environmental factors linked to where people live could also play a part in their results.
While this study has not produced conclusive results, it does point to a possible link between lithium intake and the risk of dementia, and highlights a need for more detailed research in this area. Lithium is already used to treat a number of brain conditions, including bipolar disorder, although the levels found in tap water are much lower than those used medicinally. When used as a medicine, dosage levels are key to achieving beneficial outcomes, which could explain the mixed findings of the Danish study.
Professor Simon Lovestone, from Oxford University’s psychiatry department, said: “This is a really intriguing study. Lithium is used to treat people with bipolar disorder and some studies have suggested that people on lithium for this reason – often for life – might also be protected from Alzheimer’s (the most common form of dementia).”
Dr David Reynolds, from the charity Alzheimer’s Research UK, also welcomed the Danish study as a new avenue to explore: “It is potentially exciting that low doses of a drug already available in the clinic could help limit the number of people who develop dementia,” he said.
Dr Reynolds added that if a treatment could be found that would delay the onset of dementia by just five years, it would mean 666,000 fewer people in the UK developing the condition by 2050.
Possibly the biggest problem with the Danish study is that it does not conclusively demonstrate cause and effect. In other words, while it seems to show a link between higher lithium levels in drinking water and a reduced risk of dementia, there are too many other factors which could be skewing that results. More specific research is now needed to prove a direct causal effect, and that could take several years.