A ‘game-changing’ study has found that low levels of lithium may be a hidden cause of Alzheimer’s disease – offering the hope of a simple, low-cost treatment that could protect the brain long before lasting damage begins.

The study, featured in the journal Nature, indicates that supplementing the brain with lithium could potentially decelerate or even reverse cognitive decline. Regular intake of lithium as a supplement may hold the key to preserving memory.

It’s a finding that the scientists who led the study say could one day lead to a cheap treatment for the world’s most common form of dementia.

Alzheimer’s, which causes around six in ten dementia cases, affects one million people in the UK, gradually robbing them of memory, reasoning and independence.

It’s thought to be caused by a build-up of sticky protein clumps, called amyloid plaques, between brain cells: these block the signals the brain cells use to communicate. Inside these cells, tau proteins, which help hold brain cells together and transport nutrients, twist into threads that strangle and kill the cells. Together, these changes cause the brain to shrink.

Current drugs only slow decline and carry the risk of troubling side-effects such as nausea, dizziness and sleep problems.

New medications such as lecanemab, a form of immunotherapy, have recently made the headlines after they’d been shown to remove some of the amyloid plaques.

This can slow decline a little, yet these drugs can have potentially serious side-effects such as brain swelling and bleeding. They also cost tens of thousands of pounds a year, and must be given in hospital every few weeks.

Dr Leah Mursaleen, head of clinical research at Alzheimer’s Research UK, said the findings were ‘an exciting discovery’

No therapy yet stops or reverses the disease.

In the new study, researchers from Harvard Medical School compared donated brain tissue from people who had died with Alzheimer’s with that from healthy volunteers: they discovered that lithium was strikingly depleted in the parts of the brain hit hardest by the disease.

Lithium is a naturally occurring mineral that’s found in tiny amounts in the brain, where it helps nerve cells communicate and protects them from damage. The scientists believe the drop in lithium is the result of amyloid plaques draining the mineral from the cells surrounding them.

Further experiments in mice showed the same pattern: when lithium levels dropped, the animals developed more amyloid and tau tangles. As this happened, memory also worsened.

When the researchers gave the mice with Alzheimer’s lithium orotate, a form of lithium that can reach the brain easily and doesn’t become trapped by amyloid plaques, it restored the lithium levels in their brain tissue.

It also reduced the build-up of sticky protein plaques and tau tangles, and reversed their memory problems. (The lithium was adminstered in drinking water.) Professor Bruce Yankner, a neuroscientist who led the study, said: ‘This is groundbreaking. For the first time, we can see how lithium deficiency may drive the disease – and that correcting it might undo the damage.’

The research team says the next step is to see if the same results can be achieved in people.

Early safety trials of lithium supplements could begin within two to three years, involving small groups with mild memory loss. If it proves safe, larger studies will test whether it can slow, or even prevent, Alzheimer’s.

Because lithium – perhaps best known as a treatment for bipolar disorder – is a natural substance, it can’t be patented in its basic form, so drug companies have little incentive to fund costly trials. Researchers say progress will rely on public or charity funding, unless a company develops its own new version – for example, a branded tablet or slow-release formula it can licence.

For treating bipolar disorder, doctors prescribe lithium carbonate – a cheap but tightly monitored drug that can cause side-effects if the dose is too high.

The amounts being studied for Alzheimer’s are far smaller and thought to be safer, but human trials will need to confirm that. (While small amounts of lithium are also found in drinking water and foods such as grains and vegetables, the levels in these are far too low to have a medical effect.)

Commenting on the new study, Dr Leah Mursaleen, head of clinical research at Alzheimer’s Research UK, said the findings were ‘exciting’.

‘There are different types of lithium salts already used to treat conditions such as bipolar disorder and schizophrenia,’ she told Good Health. ‘Future research will need to explore which might be best suited for testing in dementia clinical trials. We’re still a long way from knowing whether this could work in people.’

Dr Richard Oakley, associate director of research and innovation at Alzheimer’s Society, said: ‘We don’t yet fully understand the way lithium works and more research is needed, at a much larger scale, before it can be considered a safe and effective treatment.’ He added: ‘Individuals should not self-prescribe lithium as this can be dangerous.’