Nearly a hundred commonly used drugs linked to increased dementia risk.
A class of drug used for many conditions, from depression to high blood pressure, are linked to an increased risk of cognitive decline and dementia.
Anticholinergic drugs are used for conditions including bladder control, colds and hay fever.
Many of the drugs can be bought over-the-counter, without prescription.
People who took at least one anticholinergic drug were 47 percent more likely to develop mild cognitive impairment (MCI), the researchers found.
MCI is a common precursor to Alzheimer’s disease, the most common form of dementia.
Four commonly used drugs which have strong anticholinergic effects are:
- Doxepin (Sinequan) – an older antidepressant.
- Chlorpheniramine (Chlor-Trimeton) – an antihistamine used to treat hayfever.
- Diphenhydramine (Benadryl) – another antihistamine often used to treat hay fever and sometimes used to aid sleep.
- Oxybutynin (Ditropan) – for bladder control.
Dr Lisa Delano-Wood, study co-author, said:
“This study suggests that reducing anticholinergic drug use before cognitive problems appear may be important for preventing future negative effects on memory and thinking skills, especially for people at greater risk for Alzheimer’s disease.”
The study included 688 older people, none with memory problems at the outset, who were tracked for up to 10 years.
One-third were taking at least one kind of anticholinergic drug, with the average being almost five drugs per person.
Among people at high genetic risk of Alzheimer’s, those who also took anticholinergic drugs were at four times the risk of developing MCI than those not taking the drugs.
Ms Alexandra Weigand, the study’s first author, said:
“We believe this interaction between anticholinergic drugs and Alzheimer’s risk biomarkers acts in a ‘double hit’ manner.
In the first hit, Alzheimer’s biomarkers indicate that pathology has started to accumulate in and degenerate a small region called the basal forebrain that produces the chemical acetylcholine, which promotes thinking and memory.
In the second hit, anticholinergic drugs further deplete the brain’s store of acetylcholine.
This combined effect most significantly impacts a person’s thinking and memory.”
Over half the people in the study were taking double the minimum effective dose of anticholinergic drugs, the researchers found.
Almost one-in-five were taking four times the minimum dose.
Ms Weigand said
“This points to a potential area for improvement since reducing anticholinergic drug dosages may possibly delay cognitive decline.
It’s important for older adults who take anticholinergic medications to regularly consult with their doctors and discuss medication use and dosages.”
The study was published in the journal Neurology (Weigand et al., 2020).
