The American Geriatrics Society strongly recommends avoiding the use of anticholinergic medications in older adults, because seniors may be more likely to experience unwanted side effects than younger people. Anticholinergic drugs include:
• antidepressants (such as paroxetine-Paxil)
• anti-Parkinson’s drugs
• anti-psychotic drugs (such as clozapine)
• urinary bladder relaxers (such as Enablex)
• some anti-nausea drugs (scopolamine), anti-asthma drugs (ipratropium), muscle relaxants (tizanidine), antihistamines (diphenhydramine-Benadryl), and anti-seizure drugs.

One out of every three drugs prescribed for men and women over 65 are anticholinergic drugs, which are associated with increased risk for dementia (Zdr Varst, Jun 2018;57(3):140–147). A review of 21 studies involving 645,865 patients found that you are at a 46 percent increased risk for dementia if you take anticholinergic drugs for three months or more, and the longer you take these drugs the greater the risk (Neurourol Urodyn, Oct 23, 2020). Taking these drugs for mental problems increases risk even more.

Not all anticholinergic drugs are associated with increased dementia risk, but the ones that affect primarily the brain are of greatest concern. High risk for dementia occurred when anticholinergic drugs were used to treat depression or Parkinson’s disease (JAMA Internal Medicine, 2015;175(3):401-407). These studies were only on prescription anticholinergic drugs; they did not include over-the-counter drugs such as sleeping pills or antihistamines.

How Do Anticholinergic Drugs Function?
Anticholinergics block a chemical called acetylcholine that is strongly related to your ability to pay attention, learn, remember and control muscle functions. People with Alzheimer’s dementia suffer from low levels of acetylcholine. Parkinson’s disease is characterized by low levels of its opposing neurotransmitter, dopamine, that blocks the action of acetylcholine and overstimulates muscles to cause rigid muscles, jerking and shaking. Parkinson’s disease is often treated with anticholinergic medications to block the action of acetylcholine. These anticholinergic medications can cause confusion, memory loss, hallucinations, and blurry vision. Most treatments for dementia increase acetylcholine levels in your body.

Acetylcholine helps to send messages along parasympathetic nerves that control smooth muscles in the gastrointestinal tract, urinary tract, lungs, muscles, heart and other parts of the body (BMJ, April 25, 2018;361:k1315). Anticholinergic drugs are often used to treat:
• dizziness (vertigo or motion sickness)
• gastrointestinal disorders (ulcers, diarrhea, diverticulitis, ulcerative colitis, nausea, vomiting)
• genitourinary disorders (over-active bladder, incontinence, cystitis, urethritis, prostatitis)
• insomnia
• respiratory disorders (asthma, chronic bronchitis, chronic obstructive pulmonary disease)
• irregular heartbeats
• excessive salivation
• involuntary and excessive muscle movement (Parkinson’s disease, tremors)
• side effects of some anti-psychotic medications
• some poisonings such as insecticides or poisonous mushrooms
• anxiety

Early Signs of Loss of Mental Function
Symptoms of possible onset of dementia include:
• confusion
• short-term memory loss
• irrational thinking or behavior
• frequent arguing or uncontrolled anger
• making bad buying decisions or susceptibility to scams
• dropping out of a conversation
• unwarranted suspicion
• depression
• unexplained fear
• being easily upset
• forgetting names or appointments
• forgetting to pay bills
• difficulty completing tasks
• reduced ability to work with numbers
• difficulty concentrating on games, movies or television programs
• difficulty reading
• inability to carry on a logical conversation
• repeatedly losing or misplacing things
• failure to take care of usual grooming habits
• withdrawal from usual activities

My Recommendations
If you (or someone you care for) experience any of the symptoms listed above, your doctor is likely to recommend a complete workup for all of the possible causes for loss of mental function. The workup will include a review of all drugs and over-the-counter products you are taking and their possible side effects.

You can find out if a drug you are taking is an anticholinergic drug just by doing a Google search for “is [name of your drug] anticholinergic?” If you are taking any anticholinergic drugs, do not stop taking them; check with your doctor, and you will jointly decide whether you should taper off or change any of your drugs. These studies show only a potential association of anticholinergic drugs with loss of mental function; nobody has shown that they cause dementia.