Common drugs including anti-depressants could increase dementia risk by up to 50 per cent

Laura Donnelly
The study examined the links between common medications and an increased risk of dementia  - This content is subject to copyright.

Common drugs including anti-depressants could increase the risk of dementia by up to 50 per cent, a major study has found.

Experts said the findings had “enormous implications” for millions of Britons, with half of middle-aged people taking one of the medications.

The class of drugs - which are also prescribed to treat bladder conditions, Parkinson's disease and epilepsy- are called anti-cholinergic medication.

Scientists said they could be could be responsible for as many as one in 10 cases of dementia.

The study by Nottingham University, published in JAMA Internal Medicine, involved more than 280,000 UK patients over the age of 55 - including around 59,000 with a diagnosis of dementia.

Among both groups, more than half were taking some kind of anti-cholinergic drugs, which help to relax muscles, and work by blocking acetylcholine, a chemical that transmits messages in the nervous system.

Their findings showed an almost 50 per cent increased risk of dementia among patients aged 55 and over who had used strong anti-cholinergic medication daily for three years or more.

The NHS advises that these drugs should be avoided for frail older people because of their impact on memory and thinking.

But experts said the new findings suggested caution should be taken in prescribing them to anyone who is middle aged or older.

Professor Tom Dening, Head of the Centre for Dementia at Nottingham University, said: "This study provides further evidence that doctors should be careful when prescribing certain drugs that have anti-cholinergic properties.

"However, it's important that patients taking medications of this kind don't just stop them abruptly as this may be much more harmful.

"If patients have concerns, then they should discuss them with their doctor to consider the pros and cons of the treatment they are receiving."

The study was observational, so could not prove that the drugs cause dementia.

Experts said that many of the conditions the drugs are prescribed for - such as depression and Parkinson’s disease - are risk factors for dementia, which could also explain the link.

But researchers said that the findings could mean around 10 per cent of dementia diagnoses are attributable to the drugs.

This equates to around 20,000 of the 209,600 new cases of dementia per year in the UK.

Study leader Prof Carol Coupland said: "Our study adds further evidence of the potential risks associated with strong anti-cholinergic drugs, particularly anti-depressants, bladder anti-muscarinic drugs, anti-Parkinson drugs and epilepsy drugs.

"The risks of this type of medication should be carefully considered by healthcare professionals alongside the benefits when the drugs are prescribed and alternative treatments should be considered where possible, such as other types of anti-depressants or alternative types of treatment for bladder conditions."

She added: "We found a greater risk for people diagnosed with dementia before the age of 80 which indicates that anti-cholinergic drugs should be prescribed with caution in middle-aged people as well as in older people."

Prof Clive Ballard, Professor of Age-Related Diseases at the University of Exeter Medical School, said: “This is a very important finding with enormous and very practical implications that could improve brain health.”

But he said it was important to note that some of the drugs might be more likely to be prescribed to those with problems such as psychiatric symptoms and urinary incontinence which could be clues to increased risks of cognitive decline.

Dr James Pickett, Head of Research at the Alzheimer's Society, said of the findings: "Our own researchers have already shown a strong link between anticholinergic drugs and risk of dementia.

"This study builds on this information, showing that long-term, high-dose use increases risk of dementia, particularly vascular dementia."

The charity said the study could not show whether dementia might have already begun in the brains of those involved in the study, before they started taking the drugs.

An ongoing study at the University of East Anglia is trying to establish this.

Dr Pickett added: "Current guidelines for doctors say that anticholinergic drugs should be avoided for frail older people because of their impact on memory and thinking, but doctors should consider these new findings for all middle aged and older people as long-term use could raise the risk of dementia."

Dr Jana Voigt, Head of Research at Alzheimer’s Research UK, said the findings were part of a “growing body of evidence” linking the drugs to an increased risk of dementia.

“Anticholinergics can have beneficial effects that doctors need to carefully weigh against any potential side effects,” she warned.

“Anyone who is worried about their medication should seek advice from their GP before stopping any course of treatment.”