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Member Research & Reports

Member Research & Reports

Washington Study Links Certain Over-the-Counter Drugs to Dementia

Certain kinds of common medications, including antihistamines such as Benadryl, were linked to a significantly increased risk for developing dementia, according to a study by the University of Washington and Group Health Research Institute.

The study was co-authored by several researchers affiliated with the UW School of Public Health’s Departments of Biostatistics, Epidemiology, and Health Services. Researchers set out to study the cumulative effects of taking commonly used anticholinergic medications. Those drugs block the neurotransmitter acetylcholine and include first-generation antihistamines, tricyclic antidepressants, and certain medications for bladder control.

Researchers tracked nearly 3,500 seniors participating in the long-running Adult Changes in Thought, a joint Group Health – UW study funded by the National Institute on Aging. Over an average follow-up of seven years, nearly 800 study participants (or 23 percent) developed dementia (and 80 percent of these developed Alzheimer’s disease).

“Older adults should be aware that many medications — including some available without a prescription, such as over-the-counter sleep aids — have strong anticholinergic effects,” said first author Dr. Shelly Gray, a professor in the UW School of Pharmacy. “And they should tell their health care providers about all their over-the-counter use.” Dr. Gray said if providers need to prescribe anticholinergic drugs, they should use the lowest effective dose and monitor the therapy regularly to ensure it’s working.

The study was published in JAMA Internal Medicine. Senior author was Dr. Eric Larson, executive director of Group Health Research Institute and a clinical professor of medicine and of health services at the UW.