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A class of drug commonly prescribed to treat everything from depression to Parkinson’s disease may raise long-term risk of dementia by as much as 50%, according to researchers at the University of Nottingham.

The drugs, anticholinergics, help to relax and contract muscles by blocking messages to the nervous system. They are known in some cases to have short-term side effects including confusion and memory loss, but the affects of long-term use have been unclear, wrote the researchers, led by Carol Coupland, Ph.D.

Coupland’s team studied seven years’ worth of medical records from more than 280,000 older adult patients with and without dementia diagnoses. Drugs associated with the highest risk of dementia were anticholinergic antidepressants, antipsychotic drugs, anti-Parkinson’s drugs, bladder drugs and epilepsy drugs. No increased risk was found for other types of anticholinergic drugs studied, such as antihistamines and gastrointestinal drugs.

Association does not prove cause, but the research team noted that if the association is causal, around 10% of dementia diagnoses are attributable to anticholinergic drug exposure. 

Anticholinergic drugs should be prescribed with caution to older adults, but abruptly discontinuing use may be harmful, said Tom Dening, M.D., a psychiatrist and a member of the research team. Patients with concerns should “discuss them with their doctor to consider the pros and cons of the treatment they are receiving,” advised Dening in a statement.

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