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High antihistamine use among elderly increased risk for dementia, Alzheimer's disease

High use of anticholinergic medications such as antihistamines and antidepressants may increase the risks for dementia and Alzheimer’s disease in the elderly, according to study results.

Shelly L. Gray, PharmD, MS, of the University of Washington School of Pharmacy, and colleagues conducted a population-based prospective cohort study on participants from the Adult Changes in Thought study. Study participants (median age at enrollment, 74.4 years) were randomly sampled Seattle-area Group Health members recruited from 1994 to 1996. Additional participants were enrolled from 2000 to 2003.

Shelly L. Gray

Gray and colleagues assessed 10-year cumulative exposure to anticholinergics at study entry and updated the exposure as 3,434 eligible participants were followed biennially. Researchers categorized and labeled cumulative use as total standardized daily doses (TSDD), indicating how long participants were exposed to anticholinergics.

Participants most commonly used antihistamines (64.8%), bladder antispasmodics (45.6%), antiemetics (41.7%) and antidepressants (39.4%). After a mean follow-up of 7.3 years, 23.2% of participants developed dementia, and 79.9% of them were considered to have possible Alzheimer’s disease.

Participants who used anticholinergics for more than 3 years were at increased risk for dementia (adjusted HR=1.54; 95% CI, 1.21-1.96) or Alzheimer’s disease (aHR=1.63; 95% CI, 1.24-2.14) compared with those who did not use anticholinergics.

“We found that, among those with the greatest TSDD, participants with primarily past use had a dementia risk similar to those with greater recent or continuous use,” the researchers wrote. “This finding suggests that the risk for dementia with anticholinergic use may persist despite discontinuation of therapy.”

Patients taking anticholinergics should not stop their therapy without consulting a health care provider first, Gray said in a press release.

“Health care providers should regularly review their older patients’ drug regimens — including over-the-counter medications — to look for chances to use fewer anticholinergic medications at lower doses,” she said.

Disclosure: See the study for full list of relevant financial disclosures.