A study published in JAMA Internal Medicine has found a link between commonly used anticholinergic drugs, including over-the-counter treatments for hay fever and insomnia, and an increased risk of dementia in older adults. The research, led by Dr Shelly Gray from the University of Washington, followed 3,434 people aged 65 and older over a decade, finding that those who took higher doses of these medications daily for three years or more were at greater risk.
The drugs examined include antidepressants like doxepin, antihistamines such as diphenhydramine used for allergies or sleep, and oxybutynin for urinary incontinence. Nearly a fifth of the medications were bought over the counter. The study estimated that taking at least 10 mg/day of doxepin, 4 mg/day of diphenhydramine, or 5 mg/day of oxybutynin for more than three years increased dementia risk.
Experts urge caution but not panic. Dr Simon Ridley from Alzheimer's Research UK noted the study is interesting but not definitive, with no evidence that these drugs cause dementia. Dr Doug Brown from the Alzheimer's Society advised patients to consult their GP before stopping any medication, while encouraging doctors and pharmacists to consider alternative treatments when possible.
The Medicines and Healthcare Products Regulatory Agency said it would review the evidence. Johnson & Johnson highlighted that many UK hay fever products now use newer antihistamines not included in the study. Matthew Speers, representing over-the-counter drug manufacturers, stressed that these products are not intended for long-term continuous use.
