Diphenhydramine, an antihistamine commonly found in over-the-counter sleep aids and allergy medications, can negatively impact brain health and cognitive function, particularly in older adults. Several mechanisms are responsible for these negative effects:
Anticholinergic effects: Diphenhydramine is known to have anticholinergic properties, which means it can block the action of acetylcholine, a neurotransmitter essential for memory and cognitive function. This blockade can lead to temporary cognitive impairment, including memory lapses, confusion, and difficulty concentrating.
Sleep quality: While diphenhydramine is often used as a sleep aid, it can negatively impact the quality of sleep. Although it helps users fall asleep, it can disrupt the natural sleep cycle, reducing the amount of restorative deep sleep and REM sleep. This can lead to daytime drowsiness, poor cognitive performance, and reduced alertness.
Long-term use: Prolonged use of diphenhydramine has been associated with an increased risk of developing dementia and Alzheimer's disease, particularly in older adults. A study by Gray et al. (2015) found that the long-term use of medications with strong anticholinergic effects, including diphenhydramine, was linked to an increased risk of dementia in older individuals.
Gray, S. L., Anderson, M. L., Dublin, S., Hanlon, J. T., Hubbard, R., Walker, R., ... & Larson, E. B. (2015). Cumulative use of strong anticholinergics and incident dementia: a prospective cohort study. JAMA Internal Medicine, 175(3), 401-407. Link