Research led by the University of East Anglia (UEA) has found that long-term use of some anticholinergic medications such as antidepressants could lead to an increased risk of dementia.
An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. They inhibit parasympathetic nerve impulses by selectively blocking the binding of the neurotransmitter acetylcholine to its receptor in nerve cells.
Anticholinergic drugs are used to treat a variety of conditions and are found in some antidepressants and bladder medicines. In England, an estimated 1.5 to two million people take anticholinergics.
Researchers studied the medical records of 40,770 patients over 65 diagnosed with dementia and compared them with the records of 283,933 people without dementia. More than 27 million prescriptions were analysed to see if there was a link between different classes of anticholinergic medication and dementia diagnosis.
Published in the BMJ, the research found that dementia was more common among patients prescribed greater quantities of anticholinergic antidepressants, and anticholinergic drugs for urinary incontinence and Parkinson’s.
The researchers discovered that people who had been diagnosed with dementia were up to 30% more likely to have been prescribed specific classes of anticholinergic medications.
Other anticholinergic medications, including antihistamines and those used for travel sickness and abdominal cramps, were not found to be linked to dementia.
Although researchers cannot yet confirm whether anticholinergic drugs are directly linked to dementia, the study concludes that clinicians should consider long-term anti-cholinergic effects when prescribing.
Patients with concerns should continue taking their medicines until they have consulted their doctor or pharmacist.
Lead researcher from UEA’s School of Health Sciences Dr George Savva said: “What we don’t know for sure is whether the medication is the cause. It could be that these medications are being prescribed for very early symptoms indicating the onset of dementia.
“But because our research shows that the link goes back up to 15 or 20 years before someone is eventually diagnosed with dementia, it suggests that reverse causation, or confounding with early dementia symptoms, probably isn’t the case.
“This research is really important because there are an estimated 350 million people affected globally by depression, and bladder conditions requiring treatment are estimated to affect over 13% of men and 30% of women in the UK and US. Many of the treatment options for these conditions involve medication with anticholinergic effects.”