Over-the-counter sleeping tablets relied on by millions could dramatically increase dementia risk, a top US health expert has warned. 

In a recent post that has been viewed more than three million times, Dr Amy Shah implored her followers not to use products containing diphenhydramine.

These include popular medications widely available in UK pharmacies without prescription such as Nytol One-a-Night, Boots Sleepeaze and Panadol Night.

It is also found in a range of Benylin cold, flu and cough products.   

In the US, well-known brands include Tylenol PM, Unisom and allergy medication Benadryl.

Dr Shah’s intervention comes amid growing concern about research into the impact regularly taking drugs known as anticholinergics, which include diphenhydramine.

One shocking study, published in 2015, tracked 3,500 older adults found those on the tablets for three years or more had a 54 per cent higher dementia risk.

Another, published in December found there was a 22 per cent increased dementia risk in men taking another type of anticholinergic for urinary incontinence.

In a recent post that has been viewed more than three million times, Dr Amy Shah implored her followers not to use products containing diphenhydramine

Sleep aids taken by millions of people in the UK could dramatically increase dementia risk, a top US health expert has warned

In her viral post, Dr Shah said: ‘This is really important message for those who use Benadryl, Unisom, Tyleol PM, things with diphenhydramine to help you sleep.

‘Don’t do it. Don’t do it regularly because there is an increased risk of dementia – in one study 54 per cent increased risk of dementia in the elderly taking it for three years or more.’

Immunity and diet expert Dr Shah, who was trained at Harvard, Cornell and Columbia universities, adds: ‘I know it’s over-the-counter, I know you’ve had it since you were kid, but we know lot more now.

‘You should not be using these medications regularly.’

Alongside causing drowsiness, diphenhydramine has an antihistamine effect, helping to dampen allergic reactions. 

Despite this it is not used in commonly found in allergy medications in the UK, although in the US, Benadryl products do contain it. 

Dr Shag said: ‘Even for allergies, use new antihistamines like Zirtec or Allegra [sold as Allevia in the UK], Clarityn, Zyzal, because they don’t cross the blood brain barrier as much.

‘I honestly could not be more convinced that this is something you should take out of your life. 

Diphenhydramine is in medications available in UK pharmacies without prescription such as Nytol One-a-Night, Boots Sleepeaze and Panadol Night.

Dr Shah’s intervention comes amid growing concern about research into the impact regularly taking medications known as anticholinergics, including diphenhydramine

One shocking study, published in 2015, tracked 3,500 older adults found those on the tablets for three years or more had a 54 per cent higher dementia risk

‘If you know someone who uses these regularly or if you yourself use these products regularly, please stop.’

Anticholinergics block the action of acetylcholine, a chemical messenger that transmits messages in the nervous system. 

In the brain, acetylcholine is involved in learning and memory. In the rest of the body, it stimulates muscle contractions. 

Alongside antihistamines, other anticholinergics include tricyclic antidepressants, medications to control overactive bladder, and drugs to relieve the symptoms of Parkinson’s disease.

In December, a study of almost 1million British patients suggested some types of these medications can increase the risk of dementia by about third.

British experts analysed the health records of just over 170,000 patients in England over the age of 55 with dementia and compared them to 800,000 patients without the memory robbing disorder.

Overall, the authors found taking an anticholinergic was linked to an 18 per cent increased risk of dementia diagnosis.

However, they found the elevated risk to be slightly higher in men — 22 per cent, compared to women at 16 per cent.

Around 900,000 Britons are thought to have dementia, but University College London scientists estimate this will rise to 1.7 million within two decades as people live longer

The above symptoms are less well known signs of dementia — the memory-robbing condition plaguing nearly one million Britons and seven million Americans

Some specific types of the drugs often given to incontinence patients also carried a much higher risk. 

Those prescribed one, oxybutynin hydrochloride, had a 31 per cent higher risk of dementia, and those on another type, tolterodine tartrate, had a 27 per cent increased risk.

The experts said their findings emphasised the need for medics to consider alternative treatments for overactive bladder in older patients.

Alongside widespread over-the-counter use in sleep aids, NHS data suggests hundreds of thousands of prescriptions for anticholinergic are doled out on the NHS each month.

However, the authors, who published their research in the British Medical Journal, found that some types of anticholinergics weren’t linked to an increased chance of dementia.

These were darifenacin, fesoterodine fumarate, flavoxate hydrochloride, propiverine hydrochloride, and trospium chloride.

The experts also analysed a non-anticholinergic drug called mirabegron, which is also prescribed to patients with overactive bladders, but works using a different mechanism than anticholinergics.

While the scientists did find some evidence of dementia links to this drug, they noted the data wasn’t clear, and further research is needed. 

The makers of Nytol, Panadol Night, Benylin and also Boots were approached for comment.