New Delhi– Certain antihistamines, commonly used to treat allergies, may increase the risk of dementia and cognitive decline in older adults, according to a new study published in the Journal of the American Geriatrics Society.
Researchers from the University of Toronto found that elderly patients treated by physicians who frequently prescribed first-generation antihistamines faced a significantly higher risk of developing delirium — a sudden and severe state of confusion — during hospitalization.
“First-generation antihistamines, such as diphenhydramine, are among the leading causes of medication-related harms in older adults,” the study noted. “Although these medications are indicated for histamine-related conditions such as hives and anaphylaxis, they may be prescribed inappropriately.”
The research analyzed data from 328,140 patients aged 65 and older who were admitted by 755 attending physicians across 17 hospitals in Ontario, Canada, between 2015 and 2022. Results showed that 34.8 percent of these patients experienced delirium. Those treated by doctors who frequently prescribed first-generation antihistamines had 41 percent higher odds of experiencing delirium than those treated by physicians who rarely prescribed them.
Delirium affects up to half of hospitalized older adults and is linked to poor outcomes, including higher mortality rates and long-term cognitive decline, which can accelerate the onset of dementia.
“We hope our study raises awareness among hospitalists that sedating antihistamines can be harmful and should be prescribed with caution,” said Dr. Aaron M. Drucker of the University of Toronto and Women’s College Hospital, who led the research.
The study also highlighted that while first-generation antihistamines are sometimes used for histamine-mediated conditions such as urticaria or anaphylaxis, they are often prescribed for non-histamine-related issues like drug rashes or general itching — where they are ineffective and potentially risky.
Researchers concluded that non-sedating antihistamines are safer alternatives, offering similar therapeutic benefits with far fewer cognitive side effects, particularly for elderly patients. (Source: IANS)
