A drug that treats depression could be used to prevent dementia in a research breakthrough hailed by Scottish experts.

A study involving 30,000 people found that those who had been prescribed Lithium were less likely to develop the disease.

Previous studies have suggested the drug could be used as a potential treatment for those who have already been diagnosed with dementia.

Dementia is the leading cause of death in elderly Western populations, but no preventative treatments are currently available. More than 55 million people worldwide have dementia, with Alzheimer’s disease the most common form. 

After controlling for factors such as smoking, other medications, and other physical and mental illnesses, lithium use was associated with a lower risk of dementia, both for short and long-term users. 

Professor Craig Ritchie, Director of Brain Health Scotland, described the study's findings are "encouraging" and said it demonstrated the potential for using existing medications to treat dementia.

The Herald:

It has been estimated that delaying the onset of dementia by just five years could reduce its prevalence and economic impact by as much as 40 percent.

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The researchers, from the University of Cambridge, conducted a retrospective analysis of the health records of nearly 30,000 patients from Cambridgeshire and Peterborough NHS Foundation Trust. 

The patients were all over the age of 50 and accessed NHS mental health services between 2005 and 2019 and excluded excluded those with a diagnosis of mild cognitive impairment (MCI) or dementia before,or less than 1 year after, their start date.

Lithium is a mood stabiliser usually prescribed for conditions such as bipolar affective disorder and depression. “Bipolar disorder and depression are considered to put people at increased risk of dementia, so we had to make sure to account for this in our analysis,” said Dr Shanquan Chen from Cambridge’s Department of Psychiatry and lead author of the study.

Of the 29,618 patients in the study cohort, 548 patients had been treated with lithium and 29,070 had not. Their average age was just under 74 years, and approximately 40% of patients were male.

Among the group who received lithium, 53, or 9.7%, were diagnosed with dementia.

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A total of 3,244 people (11.2%) were diagnosed with the disease who had not received lithium.

However, since the overall number of patients receiving lithium was small and this was an observational study, scientists say larger clinical trials would be needed to establish lithium as a potential treatment for dementia.

The main limitation of the study is that 73% of the patients in lithium-exposed group had mania/ bipolar affective disorder (BPAD), which is a significant risk factor for dementia. 

However, researchers said results "were in the opposite direction" and were supported by sensitivity analyses.

“We expected to find that patients with bipolar disorder were more likely to develop dementia, since that is the most common reason to be prescribed lithium, but our analysis suggested the opposite,” said Chen. “It’s far too early to say for sure, but it’s possible that lithium might reduce the risk of dementia in people with bipolar disorder.

"The number of people with dementia continues to grow, which puts huge pressure on healthcare systems.

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“It’s been estimated that delaying the onset of dementia by just five years could reduce its prevalence and economic impact by as much as 40 percent.” 

The discovery of lithium as a mood-altering drug changed the course of modern psychiatry.

A naturally occurring salt, lithium's use dates to the mid-19th century but the widespread discovery is usually credited to Australian psychiatrist John Cade who introduced it for bi-polar disorder in 1949. 

During the 1960s it was found to prevent recurrences of both manic and depressive episodes

Prof Ritchie, who specialises in the Psychiatry of Ageing at Edinburgh University said:

"This is a very interesting finding from case record review that compliments previous work linking lithium treatment to reducing dementia risk. 

"Lithium itself is known to affect the protein tau in the brain which is unusually elevated in Alzheimer’s disease. 

"While much more work in this area needs to be done to see if Lithium has potential for a treatment, this is certainly encouraging and also demonstrates the potential for using existing medications to try and treat or prevent Alzheimer’s disease’