Commonly-prescribed drugs could increase dementia risk according to new study

Commonly-prescribed drugs for depression, incontinence and Parkinson’s disease could increase the risk of dementia, according to a new study.

Academics at the University of Nottingham found that there was nearly a 50% increased risk of dementia among patients aged 55 and over who had used strong anticholinergic medication daily for three or more years.

The findings showed an increased risk of dementia for anticholinergic drugs overall, and specifically for anticholinergic antidepressants, antipsychotic, anti-Parkinsons, bladder and epilepsy drugs after accounting for other risk factors for dementia.

No increased risks were found with other types of anticholinergic drugs studied such as antihistamines and gastrointestinal drugs, researchers added.

Researchers said that the new results, published in the JAMA Internal Medicine journal on Monday, alongside a similar study published in 2018, helped clarify which types of anticholinergic drugs are associated with the highest risks of dementia.

But the researchers warned that because it was an observational study no “firm conclusions” about whether anticholinergic drugs cause dementia can be drawn from it.

Lead researcher Professor Carol Coupland, from the university’s Division of Primary Care, said: “Our study adds further evidence of the potential risks associated with strong anticholinergic drugs, particularly antidepressants, bladder antimuscarinic 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 antidepressants or alternative types of treatment for bladder conditions.

“These findings also highlight the importance of carrying out regular medication reviews.

“We found a greater risk for people diagnosed with dementia before the age of 80 which indicates that anticholinergic drugs should be prescribed with caution in middle-aged people as well as in older people.”

Anticholinergic drugs help to contract and relax muscles and work by blocking acetylcholine, a chemical that transmits messages in the nervous system, researchers said.

They are prescribed to treat a variety of conditions including chronic obstructive pulmonary disease, bladder conditions, allergies, gastrointestinal disorders and symptoms of Parkinson’s disease, they added.

The study, funded by the National Institute for Health Research (NIHR) School for Primary Care Research, looked at the medical records of 58,769 patients with a diagnosis of dementia and 225,574 patients without a diagnosis of dementia, all aged 55 and over and registered with UK GPs between 2004 and 2016.

Anticholinergic drug exposure was assessed using prescription information over a decade from one to 11 years before diagnosis of dementia or the equivalent dates in control patients, and was compared between the two patient groups.

Further analysis looked at prescriptions for anticholinergic drugs up to 20 years before diagnosis of dementia.

It found that in the one to 11 years before the dementia diagnosis date or equivalent in controls, nearly 57% of patients with a diagnosis of dementia and 51% of controls were prescribed at least one strong anticholinergic drug, with an average of six prescriptions in dementia cases and four in the controls, researchers said.

The most frequently-prescribed types of drugs were antidepressants, anti-vertigo and overactive bladder drugs, researchers said.

Researchers said that the increased risk associated with these drugs indicated that, if the association is causal, then around 10% of dementia diagnoses could be attributable to anticholinergic drug exposure.

This would equate to around 20,000 of the 209,600 new cases of dementia per year in the UK, they added.

Other modifiable risk factors for dementia include 5% for midlife hypertension, 3% for diabetes, 14% for later life smoking and 6.5% for physical inactivity, researchers added.

Professor Tom Dening, head of the Centre for Dementia at the University of Nottingham, said: “This study provides further evidence that doctors should be careful when prescribing certain drugs that have anticholinergic 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.”

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