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A study found that frequently prescribed medications may heighten dementia risk, according to scientific research. The study indicated that consistent use of particular widely-prescribed medicines for treating bladder disorders, Parkinson's disease, and depression could substantially elevate dementia risk in older adults.
The research, conducted by specialists at the University of Nottingham with backing from the National Institute for Health Research (NIHR), discovered almost a 50% greater dementia risk amongst patients over 55 who had taken potent anticholinergic medicines daily for three years or longer.
Anticholinergic drugs, which help to contract and relax muscles by blocking acetylcholine, a chemical that transmits messages in the nervous system, are commonly prescribed for a range of conditions. These include chronic obstructive pulmonary disease, bladder conditions, allergies, gastrointestinal disorders, and symptoms of Parkinson's disease.
While these medications can have short-term side effects such as confusion and memory loss, it is less clear whether their long-term use increases the risk of dementia. A study led by Professor Carol Coupland from the University's Division of Primary Care, published in the JAMA Internal Medicine journal, sought to explore this further.
The research examined the medical records of 58,769 patients diagnosed with dementia and 225,574 patients without a dementia diagnosis. All participants were aged 55 and over and registered with UK GPs contributing data to the QResearch database, between 1 January 2004 and 31 January 2016.
Earlier this year Harvard Health reported on another study where team led by Shelley Gray, a pharmacist at the University of Washington's School of Pharmacy, tracked nearly 3,500 men and women ages 65 and older who took part in Adult Changes in Thought (ACT), a long-term study conducted by the University of Washington and Group Health, a Seattle healthcare system.
Participants' health was tracked for an average of seven years. During that time, 800 of the volunteers developed dementia. When the researchers examined the use of anticholinergic drugs, they found that people who used these drugs were more likely to have developed dementia as those who didn't use them. Moreover, dementia risk increased along with the cumulative dose. Taking an anticholinergic for the equivalent of three years or more was associated with a 54% higher dementia risk than taking the same dose for three months or less.
The study was first reported on in 2019. The findings revealed an increased risk of dementia associated with anticholinergic drugs overall. This was particularly noted for anticholinergic antidepressants, antipsychotic drugs, antiparkinsons drugs, bladder drugs, and epilepsy drugs, even after accounting for other dementia risk factors.
No heightened risks were identified for other types of anticholinergic drugs studied, such as antihistamines and gastrointestinal drugs. Researcher Prof Tom Dening (Centre for Dementia) 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."
The study involved 58,769 dementia patients, with an average age of 82, and 63% of them were women. Each dementia case was matched with five control patients of the same age, sex, and general practice.
Professor Coupland 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."
The Alzheimer's Society commented when the findings were published: "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 some dementias, particularly vascular dementia.
"A shortcoming of this type of study is that from this information we can't rule out whether the diseases that cause dementia might have already begun in the brains of people involved before they started taking these drugs.
"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."
A full copy of the study can be found here.