Hundreds of thousands of older people who take commonly-used drugs could be at increased risk of mental decline and death, according to a major new study by Norwich-based scientists.

The findings have been published in the Journal of the American Geriatrics Society following a study of more than 13,000 people aged over 65.

Led by researchers at the University of East Anglia, the two-year research project has shown that a side-effect of many drugs commonly used to treat depression, bladder or heart problems, epilepsy and glaucoma appears to increase the risks of both cognitive impairment and death in older people.

Findings of the study have been revealed as part of a drive to find ways of reducing risk factors for dementia which affects 820,000 people in the UK.

Lead author Chris Fox, clinical senior lecturer at Norwich Medical School at the University of East Anglia, said: 'This is the first large scale study into the long-term impact of medicines which block acetylcholine – a common brain neurotransmitter – on humans, and our results show a potentially serious effect on mortality.

'Clinicians should conduct regular reviews of the medication taken by their older patients, both prescribed and over the counter, and wherever possible avoid prescribing multiple drugs with anticholinergic effects.

'Further research must now be undertaken to understand possible reasons for this link and, in particular, whether and how the anticholinergic drugs might cause the increased mortality. In the meantime, I strongly advise patients with any concerns to continue taking their medicines until they have consulted their family doctor or their pharmacist.'

As part of the research, drugs were ranked from one to three according to the strength of this activity, with drugs scoring one having a mild effect, two a moderate effect and three causing the most serious concern.

Some of the most dangerous (score three) drugs are commonly available, including the antihistamines chlorphenamine (used in the brand Piriton) and promethazine (used in Phenergan), anti-depressants amitriptyline (used in several brands) and paroxetine (used in Seroxat) and the incontinence drug oxybutynin (used in Ditropan).

The study has been welcomed by leading dementia research charity but patients have been warned not to stop taking their medication but to speak to their doctor if they are concerned.

Susanne Sorensen, head of research at the Alzheimer's Society, said: 'This robust study provides valuable findings, and must be taken seriously. However, it is vital that people do not panic or stop taking their medication without consulting their GP.'

A spokesman for the Medicines and Healthcare products Regulatory Agency said: 'Our priority is to ensure that patients are taking acceptably safe medicines. All medicines have side-effects – no effective medicine is without risk. Our priority is to ensure the benefits of medication outweigh the risks.

'The known side-effects of anticholinergic medicines are described in the product information for prescribers and in patient information leaflets.

'Where it is known that taking a combination of medicines may increase the risk of experiencing side-effects, it will be reflected in the product information.

'It is important for people taking anticholinergic medicines not to stop taking them. If they have any questions or concerns then they should contact their doctor in the first instance.'

The UEA researchers worked in collaboration with colleagues at University of Cambridge, Indiana University and NHS clinicians. The project was funded by the Medical Research Council and the US National Institute on Aging.

kate.scotter@archant.co.uk