Many common drugs taken by the elderly increase the risk of dementia and death, according to a study of 13,000 Britons aged over 65.
The research, based at the University of East Anglia and funded mainly by the Medical Research Council, is the first to investigate the cumulative impact of “anticholinergic activity” – a side-effect of a wide range of medicines, including older antidepressants, tranquillisers and antihistamines.
These drugs interfere with acetylcholine, a brain chemical that plays a key role in cognitive functioning. About half the people in the study were taking at least one drug with anticholinergic activity.
Chris Fox of UEA, the project leader, urged doctors to review their patients’ medication and avoid prescribing multiple drugs with anticholinergic effects. However, he added, patients should continue taking their medicines until they had consulted their doctor or pharmacist.
The researchers ranked drugs on a scale of 0 to 3, according to their anticholinergic activity, and 83 had some effect, including 35 with severe activity (3 on the scale).
For each additional point on the anticholinergic scale, a patient’s chance of dying during the two-year study increased by 26 per cent, after all other factors were taken into account. Twenty per cent of participants with a total anticholinergic score of 4 or more had died by the end of the study, compared with 7 per cent of those taking no anticholinergic drugs.
In addition, patients taking anticholinergic medication performed less well on cognitive function tests. The results are reported in the Journal of the American Geriatrics Society.
David Nutt, president of the British Neuroscience Society, said the study raised particular concerns about cheap, off-patent “tricyclic” antidepressants, such as amitryptyline, imipramine and clomipramine. They should be replaced by safer SSRI antidepressants such as fluoxetine (Prozac) and paroxetine (Paxil or Seroxat), he said.
Medical experts said that for many drugs with anticholinergic action, such as the heart medicines atenolol and nifedipine, side-effects might be worth the risk. “As a cardiologist, many of the drugs I use . . . [are] proven to make people with heart disease live longer, so it’s important to balance these proven benefits against the risk,” said Tim Chico, a clinician scientist at Sheffield University.
However, it was widely agreed that doctors should review multiple prescriptions for elderly patients.