- Sleep remedies, hayfever pills and anti-depressants are linked to dementia
- The risk is greatest when high doses are taken over several years
- Risk was 54 per cent higher for people taking the highest doses
- Found a link between dementia and antihistamines Piriton and Benadryl
- Link was found with sleep remedy Nytol and anti-depressant Doxepin
- Also found with Nytol and Ditropan – treatment for an overactive bladder
Older people taking over-the-counter hayfever pills and commonly prescribed medicines are at greater risk of Alzheimer’s, warn researchers.
They found a link between dementia and the antihistamine drugs Piriton and Benadryl, as well as sleep remedy Nytol, and older antidepressants.
The risk is greatest when high doses are taken over several years, says the US study.
Popular hayfever pills such as Benadryl and Piriton, sleep remedy Nytol, Ditropan – which is used to treat an overactive bladder, and the antidepressant doxepin have all been linked to dementia
These anticholinergic medications affect the brain by blocking a key chemical messenger called acetylcholine, which has a range of functions in the body.
Up to half the UK’s elderly population are prescribed at least one medication with anti-cholinergic properties, especially in care homes.
US study leader Professor Shelly Gray, director of the geriatric pharmacy program at the University of Washington School of Pharmacy, said: ‘Older adults should be aware that many medications – including some available without a prescription, such as over-the-counter sleep aids – have strong anticholinergic effects.
‘And they should tell their health-care providers about all their over-the-counter use.
‘Of course, no one should stop taking any therapy without consulting their health-care provider.
‘Health-care providers should regularly review their older patients’ drug regimens – including over-the-counter medications – to look for chances to use fewer anticholinergic medications at lower doses.’
Research last year linked the use of anticholinergic drugs and mental impairment in the elderly.
But the new study, published in the journal Jama Internal Medicine, is the first to show the higher the dose, the higher the risk of dementia.
Researchers tracked the health of 3,434 men and women aged 65 and over for around seven years while monitoring their use of anticholinergic drugs.
Of the total, 637 developed Alzheimer’s disease and 160 other forms of dementia.
WHICH MEDICINES ARE LINKED TO ALZHEIMER’S?
Researchers found a link between anticholinergic medications and dementia.
Anticholinergic medications affect the brain by blocking a key chemical messenger called acetycholine, which has a range of functions in the body.
People taking the following drugs for more than three years have an increased risk of dementia:
- At least 10 milligrams(mg) per day of the antidepressant doxepin,
- Four mg per day of diphenhydramine (Nytol, Benadryl) or
- Five mg per day of oxybutynin (Ditropan) for overactive bladder
For those taking the highest doses of these drugs, the risk of dementia was increased by 54 per cent after seven years, compared with no use.
The risk of Alzheimer’s – the most common form of dementia – was increased by 63 per cent.
For those taking the highest doses of anticholinergic drugs over the study period, the relative risk of dementia was increased by a statistically significant 54 per cent compared with no use.
The risk of Alzheimer’s was raised by 63 per cent, says the study.
People taking at least 10 milligrams(mg) per day of the antidepressant doxepin, four mg per day of diphenhydramine (Nytol, Benadryl) or five mg per day of oxybutynin (Ditropan) for overactive bladder for more than three years would have an increased risk of developing dementia.
Substitute drugs that do not have anticholinergic effects include selective serotonin re-uptake inhibitor (SSRI) antidepressants such as Prozac and newer antihistamine allergy treatments such as loratadine (Claritin), said Professor Gray.
She said: ‘If providers need to prescribe a medication with anticholinergic effects because it is the best therapy for their patient, they should use the lowest effective dose, monitor the therapy regularly to ensure it’s working, and stop the therapy if it’s ineffective.’
The researchers pointed out that anticholinergic effects in animals had been shown to increase levels of beta-amyloid protein in the brain, one of the hallmarks of Alzheimer’s.
Anticholinergic drugs block a nervous system chemical transmitter called acetylcholine, leading to side effects that may include drowsiness, blurred vision and poor memory. People with Alzheimer’s disease are known to lack acetylcholine.
The study suggested the raised dementia risk persisted even after people stopped taking anticholinergic drugs.
The study concluded: ‘Given the devastating consequences of dementia, informing older adults about this potentially modifiable risk would allow them to choose alternative products and collaborate with their health care professionals to minimise overall anticholinergic use.’
Dr Simon Ridley, head of research at Alzheimer’s Research UK charity, said: ‘This large study adds to some existing evidence linking anticholinergic drugs to a small increased risk of dementia, but the results don’t tell us that these drugs cause the condition.
‘Continued research to shed light on these links will be important for helping understand the benefits and potential risks of these drugs.
For people who took the highest doses of these drugs for the seven-year study period, the risk of dementia was increased by a statistically significant 54 per cent compared with no use. The risk of Alzheimer’s was raised by 63 per cent
‘In the meantime, anyone who is worried about the medication they are taking should seek advice from a doctor or pharmacist before stopping a course of treatment.’
The researchers compared the use of different anticholinergic drugs by calculating how many days each participant would have taken any one of the drugs for.
They then analysed the risk of developing dementia for people who had taken the drugs for different amounts of time. The link was only clear for those who had taken drugs for three years or more.
Dr Doug Brown, director of research and development at Alzheimer’s Society charity, said: ‘There have been concerns that regular use by older people of certain medications with anticholinergic effects, such as sleep aids and hayfever treatments, can increase the risk of dementia in certain circumstances, which this study supports.
‘However, it is still unclear whether this is the case and if so, whether the effects seen are a result of long-term use or several episodes of short-term use.
‘We would encourage doctors and pharmacists to be aware of this potential link and would advise anyone concerned about this to speak to their GP before