It has long been known that common over-the-counter and prescription drugs used for health issues such as depression, allergies, colds, heart disease and high blood pressure are linked with dementia and other cognitive impairment. A new study, published April 18 in JAMA Neurology, may have revealed the reason why.
The drugs are called anticholinergic (AC) medications, and they are known by such brand names as Benadryl, Paxil, Zyprexa, Dimetapp and Unisom. The new study, from the Indiana University School of Medicine, looked at cognitive test results and brain scans from 451 adults with an average age of 73. Sixty of those participants had been taking AC medications for at least a month. None of them had been diagnosed with any cognitive problems such as dementia or Alzheimer’s.
One indicator of brain activity is the level of glucose processing in the brain. The scans of the study participants who had been taking AC drugs showed lower levels of brain glucose. They also had reduced brain volume, as well as thickness in some regions that are linked to cognitive function. The researchers also found that the people using AC drugs scored lower on tests of executive function and memory recall than the participants who were not taking the medications.
Lead study author Shannon Risacher told Reuters Health, “There are definitely medical benefits to all of the anticholinergic medications we looked at, which could outweigh the cognitive risks….But if alternative therapies are available that provide effective treatment of these conditions, patients and doctors might want to consider avoiding anticholinergic medications.”
There were some limitations to the study that the authors acknowledge. For instance, while it shows an association between AC drugs and cognitive differences, it does not prove that the mental differences were actually caused by the medications. In addition, the studied relied on the participants’ accurate memory of their use of AC drugs, which was not verified by medical records. The specifics on dosage and length of time on the drugs was also vague.
However, it does add to the previous evidence showing the link between common medications and cognitive problems, and offers a new explanation for why the link might exist.
Alain Koyama, who was not involved in the study, is an outcomes researcher at Health Advocate in Los Angeles. Koyama said that the findings of the study should encourage physicians and their patients to discuss AC drugs, and consider the risks and benefits before deciding to use them, particularly since the effects on cognitive function will likely take years to appear.
Koyama added, “On the other hand, a healthier patient particularly concerned about future dementia risk, whether because of family history or other reason, may consider alternative treatments.”