Long-term use of some anticholinergic medications are associated with an increased risk of dementia - according to a new study led by the University of East Anglia (UK).
Researchers said patients who take them for more than a year, were 30% more likely to develop dementia. These interrupt a neurotransmitter involved in regulating some of the body's most basic functions, as well as playing a role in thinking...
The study was carried out by researchers from the United Kingdom and the US and looked at data for just under 41,000 patients aged 65-99 with a dementia diagnosis and just under 300,000 controls without dementia, making this the largest study of its kind to date. And while evidence for a mechanistic link between anticholinergic drugs and dementia incidence is limited, "neuropathological studies in humans and mice do support a role of anticholinergics affecting neurodegenerative pathology", they write. However, experts said that patients should keep taking their treatment, as the benefits are higher than the risks of not taking them.
A total of 14,453 (35%) cases and 86,403 (30%) controls were prescribed at least one anticholinergic drug with an ACB score of 3 during this period. "But we know from other research that people with long-term health conditions really only take their medication as prescribed around half of the time - the other half, people either take more or less of their medication or not at all".
Dr Doug Brown, Chief Policy and Research Officer at Alzheimer's Society, said: "This large study confirms that some anticholinergic drugs can raise the risk of dementia - but it should also put minds at ease as there appears to be no dementia risk with anticholinergic drugs used to treat common conditions like hayfever, travel sickness and stomach cramps".
However the dose-response link was only seen for certain classes of anticholinergic drugs, including the antidepressants amitriptyline, dosulepin and paroxetine, and urologicals including oxybutyrin and tolterodine.
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Dementia was linked to increasing exposure to antidepressant, urological and antiparkinson drugs.
Patients with concerns should continue taking their medicines until they have consulted their doctor or pharmacist. "It's a long-term effect so don't suddenly stop taking medication". It's a diverse group, with each individual drug used to treat a huge list of conditions, from hay fever and lung conditions to incontinence and depression, and millions around the world take them daily.
Alzheimer's Research UK research director Dr Carol Routledge said: "The study didn't investigate what might cause this link between anticholinergics and dementia risk, and researchers will need to build on these findings in future studies".
"While there are important advantages to research that uses the rich data held in medical records, we know that less than 70 per cent of people with dementia receive a formal diagnosis, and this study may not tell the whole story". The early symptoms of dementia include depression and urinary incontinence, so it is possible the drugs were sometimes being prescribed for people who already had the early stages. Not taking the medications could have serious consequences, he said.
"Doctors and patients should therefore be vigilant about using anticholinergic medications". "Further research is needed to understand possible reasons for this link".
"This study shows that some anticholinergics may cause long-term harm in addition to short-term harm".