Do hay fever medications increase dementia risk?

Do hay fever medications increase dementia risk?

A new study suggesting that certain hay fever medications, like Piriton and Benadryl, may increase the risk of Alzheimer's disease in older people. The findings will have caused great concern among those who rely on medications as part of their hay fever treatments. Common hay fever symptoms are a runny nose and eyes, nasal congestion and sneezing. However, it is worth taking a closer look at this study before stopping these medicines for fear of developing dementia in the future.

There is a wide range of allergy medicines on the market in the UK. Some purchased over the counter from the pharmacy, others prescribed by your doctor. The ingredients also vary and have changed over the years. In particular, there has been a move away from antihistamines (drugs that relieve your symptoms by blocking histamine) that cause drowsiness. The newer generation ' non-drowsy' antihistamines, like Piriteze, contain different ingredients.

The study, from researchers at the University of Washington, USA, focused on prescription-only drugs which contain an ingredient that have an anticholinergic effect. They work by blocking a chemical called acetylcholine, which plays many roles in the brain and nervous system. It is plausible – though not proven – that such drugs may affect the brain, over a long period of time, and lead to dementia. The anticholinergic drugs studied included antihistamines (which would include some hayfever meds), antidepressants and drugs to control the bladder.

There were 3,434 participants in the study, all over 65 and none having dementia at the start of the study. They were tracked for 7.3 years on average to see which developed dementia, including Alzheimer's disease. The researchers also recorded information on which anticholinergic medications had been taken and for how long. During the study time, 23.2 per cent of the group developed dementia, with most cases being Alzheimer's disease. The longer the anticholinergic medications had been taken, the greater the risk of dementia. For those taking the drugs for 3 years or more, the risk was 54% higher. Findings for those taking the drugs for shorter periods of time showed an increase in dementia risk, but not one that could be considered statistically significant.

The study did include antihistamines containing the anticholinergic ingredient chlorphenamine (found in Piriton) and diphenhydramine (found in Nytol, the sleeping tablet). A significant risk was found with drugs containing the following:

• Xybutynin chloride
• Chlorpheniramine maleate
• Olanzapine
• Meclizine hydrochloride
• Doxepin hydrochloride

It is likely that your allergy medications do not contain any of these ingredients. But if you are not sure, check with your pharmacist and/or have a medication review with your GP. The worst thing anyone can do is to act on a media story and stop taking prescribed medication as a result. There are nearly always a number of alternative medications for a condition, including allergies, and your GP should be able to prescribe something else if you have safety concerns.

Furthermore, if you do have an allergy, remember that allergen avoidance is key and a successful avoidance plan may help you decrease medication. An allergy air purifier can improve air quality and reduce allergen exposure and may form a useful part of an avoidance strategy.

Source: Gray S, Anderson M, Dublin S et al (2015). Cumulative Use of Strong Anticholinergics and Incident Dementia. JAMA Internal Medicine, Online First January 25
Search for this story on NHS Choices for a balanced view.

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