Study suggests some anticholinergic drugs linked with increased risk of developing dementia in older adults

Results of a case-control study published in the BMJ found "a robust association" between some classes of anticholinergic drugs and an increased risk of developing dementia in the future in older adults. The data suggest that the risk of dementia increased with greater exposure for anticholinergic drugs used to treat depression, bladder conditions and Parkinson's disease, but not for antispasmodics, antipsychotics and antihistamines.

Lead researcher George Savva noted that the analysis included "patients with a new dementia diagnosis and looked at what anticholinergic medication they were prescribed between four and 20 years prior to being diagnosed." Savva said "we found that people who had been diagnosed with dementia were up to 30 percent more likely to have been prescribed specific classes of anticholinergic medications. And the association with dementia increases with greater exposure to these types of medication."

The scientists studied the medical records of 40 770 patients aged over 65 diagnosed with dementia, and compared them to the records of 283 933 people without dementia, with more than 27 million prescriptions analysed. Results showed that 35 percent of those diagnosed with dementia were prescribed at least one anticholinergic drug with an ACB score of 3, indicating definite anticholinergic activity, while 30 percent of the control group received a similar medicine.

However, Savva cautioned "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." Savva added "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."

Ian Maidment, lead pharmacist on the study, said "we already have strong evidence that anticholinergics cause confusion and in the short-term will potentially worsen the symptoms of dementia." Maidment added "this study shows that some anticholinergics may cause long-term harm in addition to short-term harm." Meanwhile, study co-author Louise Robinson suggested that "the findings will help doctors in deciding which drugs can or cannot be used safely in the long-term as people age."

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