The long-term use of a class of drugs commonly used to treat a number of medical conditions, including depression, bladder problems, epilepsy and Parkinson’s disease, may increase the risk of dementia among older adults, according to a large British study published this week in JAMA Internal Medicine.
The drugs are anticholinergics, which help contract and relax muscles by blocking acetycholine, a chemical that aids the transmission of messages throughout the nervous system.
The study found that people aged 55 and older who had used these medications daily for three years or longer were about 50 percent more likely to develop dementia than people in that age group who had not taken the drugs.
That doesn’t necessarily mean the drugs cause dementia. This was an observational study, and therefore can show only a correlation between anticholinergics and dementia, not a direct cause-and-effect relationship. Still, as background information in the study points out, these drugs are already known to have short-term side effects that include confusion and memory loss. The new study’s findings offer the strongest evidence to date that anticholinergics may also have a long-term effect that increases the risk of dementia.
“This study provides further evidence that doctors should be careful when prescribing certain drugs that have anticholinergic properties,” said Dr. Tom Dening, one of the study’s authors and a professor of dementia research at the University of Nottingham, in a released statement.
“However, it’s important that patients taking medications of this kind don’t just stop them abruptly as this may be much more harmful,” he added. “If patients have concerns, then they should discuss them with their doctor to consider the pros and cons of the treatment they are receiving.”
For the study, Dening and his colleagues looked at medical records collected from 58,769 British adults aged 55 and older who were diagnosed with dementia between 2004 and 2016. Sixty-three percent of them were women, and their mean age when they were diagnosed with dementia was 82. The researchers then matched these patients with 225,574 “control” patients who were of the same age and gender and who went to the same general practitioner clinics around the same time.
The researchers searched the medical records for any use of anticholinergic drugs in the one to 11 years before each patient’s dementia was diagnosed — or in an equivalent period for the control patients. The drugs included antihistamines (for allergies), antiemetics (for nausea and vomiting), antidepressants, antipsychotics, antispasmodics (for stomach spasms brought on by irritable bowel syndrome and other conditions), muscle relaxants, bladder antimuscarinics (for an “overactive” bladder) and drugs used to treat epilepsy and the symptoms of Parkinson’s disease.
After adjusting the data for various confounding factors that can affect the risk of dementia (such as age, body mass index, smoking, alcohol use, ethnicity, socioeconomic status and various medical conditions), the researchers found that the use of anticholinergic drugs was associated with an increased risk of dementia that ranged from 6 percent to 49 percent, depending on the dose of the drug and how long it was taken.
The greatest risk was for people who took strong daily doses of anticholinergic drugs for at least three years. The types of anticholinergic drugs associated with the highest risk were antidepressants, antipsychotics, antiepileptics, anti-Parkinson’s disease drugs and bladder antimuscarinics.
The study did not find any increased risk of dementia with the use of antihistamines, antispasmodics or muscle relaxants.
Assessing both risks and benefits
The risk of using anticholinergics “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 condition,” said Carol Coupland, the study’s lead author and a medical statistician at the University of Nottingham, in a released statement.
The study’s findings also underscore the importance of doctors and patients conducting regular reviews of their medications, she added.
“We found a great 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,” Coupland said.
Although this observational study cannot prove a direct cause-and-effect relationship between anticholinergic medications and dementia, if the relationship is causal, it would mean that about 10 percent of dementia cases could be attributed to these drugs, the study’s authors point out in their paper.
An estimated 5 million Americans are currently living with dementia.
FMI: You can read the study in full on the JAMA Internal Medicine website.