Do Over-the-Counter Drugs Come with Increased Risk of Dementia?

A recent US study has suggested that some sleeping drugs and hayfever treatments may increase the risk of Alzheimer’s disease. Also amongst the medications were some older style anti-depressants and bladder control treatments. Scientists identified over-the-counter medicines such as Nytol, Piriton and Benadryl as those that could raise the likelihood of dementia in later life. 

What are Anticholinergic Drugs?

These medications all belong to a class of drug known as “anticholinergic”, which have a particular blocking method on the nervous system. Anticholinergic drugs work by blocking a chemical transmitter called acetylcholine. Studies on people with Alzheimer’s disease have shown that they suffer from a lack of acetylcholine.

The study took place at the University of Washington, and was subsequently published in JAMA International Medicine. It processed data from some 3,434 men and women aged over 65 for seven years, whilst simultaneously recording their use of anticholinergic drugs. The results showed that there was an increased risk of developing Alzheimer’s when higher amounts of the anticholinergic drugs were taken.

The study revealed that people were at risk if they took:

• 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

The research showed that those on the largest doses were at a 54% higher risk than those who took none, with the risk of Alzheimer’s at 63% higher.

Professor Shelly Gray, director of the geriatric pharmacy programme at the University of Washington School of Pharmacy, who led the study 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 healthcare providers.”

What should you do?

She advised patients not to stop taking their medications, but to visit their GP and ask for an alternative with ‘fewer anticholinergic medications at lower doses’.

There has been similar research which shows a link between anticholinergic drugs and a higher risk of Alzheimer’s disease, but this is the first study to show that a larger dose is also a factor.  

The study also revealed that another effect of anticholinergic drug use in animals increased the beta-amyloid protein levels in the brain. These are the proteins that clump together in the brain and stop neurons from firing effectively, and is a cause of Alzheimer’s.

However, not all experts in dementia are convinced by the results. Dr Simon Ridley, of Alzheimer’s Research UK, believes that more research is needed: “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.”

Further Reading

You can find a series of thought-provoking updates about Alzeimers in a number of posts on the Labmate website – these include: antidepressants could slow down Alzheimer's, test reveals Alzheimer's disease ten years before symptoms appear and new genes identified that link to Alzheimer's.