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What Is the Link Between Anticholinergic Drugs and Dementia Risk?

Medically Reviewed by Poonam Sachdev on October 12, 2022

Devil's Breath, also known as scopolamine or hyoscine, is a tropane alkaloid that's used to treat various medical issues like nausea, vomiting, motion sickness, and even muscle spasms. All alkaloids are organic and naturally occurring compounds with at least one nitrogen atom, and tropane alkaloids (TAs) are specific a class of alkaloids that contain over 200 known compounds and form a tropane ring system.

What Are Anticholinergic Drugs?

Anticholinergic drugs are a group of drugs made from the belladonna plant. This plant, also called deadly nightshade, is poisonous at certain doses. Despite this, it’s also used in some medications because of the way it suppresses the nervous system.

Your nervous system is the network of nerves throughout your body. First, your brain gives orders. Your nerve cells then relay those commands throughout the body. Your nervous system controls things like movement, thought, heart rate, breathing, sleep, and your senses.

Neurotransmitters carry chemical signals through your nervous system. Anticholinergic drugs work by suppressing the neurotransmitter acetylcholine, selectively slowing down the parasympathetic nervous system.

There are many medical uses for anticholinergic drugs, such as:

General use. Anticholinergic drugs may be used to treat:

  • Allergies
  • Cardiovascular disease
  • Depression
  • Excessive sweating
  • Insomnia
  • Intestinal cramps or spasms
  • Loss of bladder control
  • Nausea
  • Painful menstruation
  • Parkinson’s disease
  • Psychiatric disorders
  • Respiratory disorders such as asthma and COPD
  • Stomach cramps or spasms
  • Vomiting

Surgical use. Anticholinergic drugs are sometimes used in surgical settings to calm the nervous system. Surgical uses for anticholinergic drugs include:

  • Decreasing secretions like saliva
  • Promoting relaxation before anesthesia
  • Preventing nausea and vomiting after anesthesia and surgery
  • Regulating your heart rate
  • Relaxing your stomach and intestines prior to certain procedures

Poisoning antidote. Anticholinergic drugs can be used to counteract certain poisons. These include some types of:

  • Medications
  • Mushrooms
  • Nerve gasses
  • Organic phosphorus pesticides

Anticholinergic Drug Examples

There are many types of anticholinergic drugs, and they come in many forms like pills, eye drops, and injections depending on their use. Common anticholinergic drugs and popular brand names include:

  • Benztropine, brand name Cogentin. Used to treat symptoms of Parkinson’s disease.
  • Biperiden, brand name Akineton. Used to treat symptoms of Parkinson’s disease.
  • Darifenacin, brand name Enablex. Used to treat an overactive bladder.
  • Diphenhydramine, brand name Benadryl. Used to treat allergies and allergic reactions.
  • Dicycloverine, brand name Bentyl. Used to treat irritable bowel syndrome.
  • Glycopyrrolate, brand name Robinul. Used to treat peptic ulcers and excessive drooling.
  • Hyoscyamine, brand names Cystospaz, Ed-Spaz, Hyomax, Hyosyne, IB-Stat, Levsinex, Neosol, NuLev, Oscimin, PRO-HYO, Spasdel, and Symax. Used to treat muscle cramps in the bowels or bladder.
  • Orphenadrine, brand name Norflex. Used as a muscle relaxer.
  • Oxybutynin, brand names Ditropan and Oxybutynin. Used to treat an overactive bladder. 
  • Scopolamine, brand names Scopodex and Transderm-Scop. Scopodex is used to regulate heartbeat during surgery. Transderm-Scop is used in skin patches for nausea and vomiting.

What Is Dementia?

Dementia is a general term used when someone’s ability to think, remember, or make decisions is impaired. Dementia is most common in elderly patients. In 2014, the Centers for Disease Control and Prevention (CDC) estimated that there were 5 million adults over the age of 65 with dementia.

There are several different types of dementia, but the most common is Alzheimer’s disease. Alzheimer’s makes up 60 to 80% of dementia cases.

Dementia may negatively affect your:

  • Attention levels
  • Communication
  • Judgment
  • Memory
  • Reasoning and problem-solving
  • Visual perception

Some forms of dementia, like Alzheimer’s and frontal-lobe dementia, may also cause personality and behavioral changes. Motor skills may decline in the cases of Alzheimer’s and Lewy body dementia.

Some people are at a higher risk of dementia than others. Significant risk factors include:

  • Age. Increasing age is the strongest risk factor for dementia.
  • Heart problems. A history of high blood pressure, high cholesterol, and stroke can lead to vascular dementia.
  • Genetics. Having a close relative with Alzheimer’s increases your risk of contracting it by 10 to 30%.
  • Race/ethnicity. Some racial groups are at a higher risk of developing dementia than others. Older African-Americans are twice as likely to develop dementia as white people, and Hispanic people are 1.5 times more likely.
  • Traumatic brain injury. Severe or recurring head injuries can increase your risk of dementia.

Sometimes, dementia is temporary. If so, it is typically found to be a side effect of things like certain medications, vitamin deficiency, and thyroid hormone imbalance.  

Do Anticholinergic Drugs Cause Dementia?

Several years ago, researchers conducted a study to look at a possible link between anticholinergic drugs and dementia risk. This was not a randomized control trial, but it was large, with nearly 3500 participants, and lasted ten years. Participants were 65 and older, and at the start of the study, they did not have a diagnosis of dementia. 

Researchers recorded what medications the participants were taking. This included prescription anticholinergic drugs, as well as over-the-counter medications like Benadryl. Each participant had their cognitive faculties assessed when they entered the study and every two years after that. 

By the end of the study, 797 participants had developed dementia. Of those, 637 were judged to possibly or probably have Alzheimer's.

When looking at the data, researchers found a significant correlation between patients who took anticholinergic drugs and those who had dementia. It also found that the higher the total amount of anticholinergic drugs taken over the ten-year study, the greater the risk of dementia. 

Patients who had the highest exposure levels, equivalent to taking a regular dose for three years, were significantly more likely to have dementia and Alzheimer's disease than those who did not take anticholinergic drugs.

At the next level of exposure, patients still had an elevated risk of dementia and Alzheimer's, though not as much as the group with the highest level of exposure. 

The study also found that:

  • The type of anticholinergic medication did not make a difference
  • Recent depressive episodes did not increase dementia risk
  • The timing of the use of anticholinergic use did not make a difference

So, why is there a link between these medications and dementia? One leading theory is that the lack of acetylcholine may lead to Alzheimer’s disease since patients with Alzheimer’s disease have lower levels of acetylcholine. This has such a large influence on the way that Alzheimer’s disease progresses that medications to prevent the brain from breaking down acetylcholine are prescribed to ease Alzheimer’s symptoms. 

Anticholinergic drugs inhibit acetylcholine, which could create an effect similar to the acetylcholine decline associated with Alzheimer's. Further research and testing are needed.

Show Sources

SOURCES:
Alzheimer’s Society: “How do drugs for Alzheimer's disease work?.”
Centers for Disease Control and Prevention: “About Dementia.”
Cleveland Clinic: “Nervous System,” “Neurotransmitters.”
Ghossein, N., Kang, M., Lahkar, A. StatPearls, “Anticholinergic Medications,” StatPearls Publishing, 2022.
GoodTherapy: “Acetylcholine.”
JAMA Internal Medicine: “Cumulative Use of Strong Anticholinergics and Incident Dementia A Prospective Cohort Study.”
Mayo Clinic: “Anticholinergics And Antispasmodics (Oral Route, Parenteral Route, Rectal Route, Transdermal Route),” ““Biperiden (Oral Route),” “Orphenadrine (Oral Route),” “Scopolamine (Transdermal Route).”
MedlinePlus: “Benztropine,” ““Darifenacin,” “Dicyclomine,” “Diphenhydramine,” “Hyoscyamine,” “Oxybutynin.”
U.S. Forest Service: “The Powerful Solanaceae: Belladonna.”

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