Overview
- Citing Friday's JAMA Internal Medicine study as reported by Harvard Health, researchers analysed about 3,500 people aged 65 and over and found three years or more of strong anticholinergic use was associated with a 54% higher risk of dementia compared with short-term use.
- Diphenhydramine, the active ingredient in many US Benadryl products, is named among the anticholinergic drugs linked to the association but the researchers stressed the study shows correlation not proof of causation.
- Anticholinergic drugs work by blocking acetylcholine, a brain chemical involved in memory, and experts warn that taking multiple medicines with anticholinergic effects can add to cognitive risk.
- The NHS and the Alzheimer’s Society advise older people to speak with a GP or pharmacist before changing or stopping treatments and note UK Benadryl formulations often use different antihistamines such as acrivastine or cetirizine.
- Clinically, the result may prompt medication reviews for long-term users of anticholinergic antihistamines and encourage consideration of newer non‑drowsy alternatives or other allergy strategies while further research seeks to confirm causation.