A study links the long-term use of some drugs with a higher risk of dementia.
Savva's group studied the medical records of 40,770 patients, ages ≥65, who were diagnosed with dementia, comparing them with 283,933 controls.
The study also analyzed over 27 million prescriptions.
For drugs previously associated with delirium, the highest odds were seen with anticholinergic drugs for Parkinson's (adjusted OR 1.29, 95% CI 1.11-1.50, P 0.01) and bladder conditions (adjusted OR 1.18, 95% CI 1.13-1.23, P 0.01), reported George Savva, PhD, of the University of East Anglia in Norwich, England, and colleagues.
But those individuals taking other classes of anticholinergics - including those used for asthma and gastrointestinal issues - were not at an increased risk of developing dementia compared with matched controls, the study found. This allowed the researchers to show that some types of anticholinergic medications were not associated with the onset of dementia. The researchers found that there was a significant association between dementia and drugs for depression, Parkinson's and urological conditions with the risk of dementia increasing by 11%, 29% and 18% respectively in patients on anticholinergics.
In the meantime, they say clinicians "should continue to be vigilant with respect to the use of anticholinergic drugs, and should 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". "That means pharmacists, doctors and nurses working with patients who are prescribed multiple drugs, to ascertain if the benefits clearly outweigh the potential harm that could be caused by anticholinergics". 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.
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The exact reasons for the increased risk of dementia among those taking certain anticholinergic medications remain unclear. Not taking the medications could have serious consequences, he said.
The researchers, who report their findings in the British Medical Journal, investigated GP records for more than 40,000 people over the age of 65 with dementia and almost 300,000 without dementia.
The number of older people taking five or more medicines has quadrupled in the past two decades, fuelling the need for more research into the effects of taking a "cocktail" of prescribed drugs, Maidment said.
"We don't know exactly how anticholinergics might cause dementia".
The new study is among the largest of its kind and adds to the existing literature linking long-term anticholinergic use with dementia, according to Dr. Clive Ballard, executive dean of University of Exeter Medical School, who was not involved in the research. "It's a long-term effect so don't suddenly stop taking medication". Nevertheless, the team claims, the findings are signficant enough to warrant reduced prescribing anticholinergics, where possible "With many medicines having some anticholinergic activity, one key focus should be de-prescribing", states study co-researcher Ian Maidment, Ph.D., senior lecturer in clinical pharmacy at Aston University in the United Kingdom. "Specifically, for most highly anticholinergic drugs, non-pharmacological and pharmacological alternatives are available and should be considered", they conclude.