a man taking tablet imageApril 30 2018

Anticholinergic drugs used in helping control some involuntary muscle movement conditions have been found to be associated with an increased risk of dementia.

The study, described as the largest of its kind to date, has prompted researchers to say that clinicians should avoid long term prescribing of some anticholinergics to patients aged 45 and over. They should also “consider the risk of long term cognitive effects, as well as short term effects, associated with specific drug classes when performing their risk-benefit analysis.”

Researcher from the University of East Anglia assessed data from the UK’s Clinical Practice Research Database for 40,770 patients aged 65 to 99 years who were diagnosed with dementia between April 2006 and July 2015. Each case patient was matched to up to seven control patients of similar age and sex, but without dementia.

The researchers gave a score to drugs according to their anticholinergic activity using the Anticholinergic Cognitive Burden (ACB) scale. An ACB score of 1 was classed as possibly anticholinergic, while a score of 2 or 3 was definitely anticholinergic. Patient histories ranging from four to 20 years were then evaluated.

“When considered by drug class, gastrointestinal drugs with an ACB score of 3 were not distinctively linked to dementia. The risk of dementia increased with greater exposure for antidepressant, urological, and anti-Parkinson drugs with an ACB score of 3. This result was also observed for exposure 15-20 years before a diagnosis,” said the researchers.

“This could be caused by a class specific effect, or by drugs being used for very early symptoms of dementia” and they called for further research into the effects of specific drug classes.

Dr Doug Brown, Chief Policy and Research Officer at the Alzheimer’s Society, which funded the new study, said: “This large study confirms that some anticholinergic drugs can raise the risk of dementia – but it should put minds at ease as there appears to be no dementia risk with drugs used to treat common conditions like hay fever, travel sickness and stomach cramps.

“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 over-65s as long-term use could raise the risk of dementia.”

Frequently prescribed anticholinergic drugs listed by Alzheimer’s UK included: 

  • anti-depressants – amitriptyline, dosulepin and paroxetine;
  • bladder medications – tolterodine, oxybutynin and solifenacin;
  • Parkinson’s treatment – procyclidine.

Parkinson’s UK has advised patients that “these drugs are old and are now rarely used for Parkinson’s. Sometimes they are prescribed for reducing tremor and muscle stiffness.

“One of the reasons that these medications are not often given to people with Parkinson's is because they can cause memory problems or make them worse. Anyone with Parkinson's who is taking anticholinergics should be carefully monitored by their specialist or Parkinson's nurse.”

Professor David Dexter, Deputy Research Director at Parkinson’s UK, added: “The research published this week shows us that there is a link between anticholinergic drugs and dementia but it does not tell us why. It could be that people who are in the very early stages of dementia are more likely to be prescribed these drugs for other reasons.

“It’s also important to point that other factors – such as unhealthy lifestyles – have a far greater impact on risk of dementia.”

BMJ announcement      
K Richardson et al. ‘Anticholinergic drugs and risk of dementia: case-control study’. BMJ 2018;361:k1315. Published 25 April 2018
Alzheimer’s UK announcement 
Parkinson’s UK announcement