Long-Term Use of These Drugs May Increase Risk for Dementia

Nicole Zhao ’20

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Figure 1. Short-term effects of drugs may be apparent but long-term effects are largely unstudied.

A diagnosis of dementia is often accompanied by fear, anxiety and the need to fulfill a bucket list before the condition robs you of life. Dementia is the loss of cognitive functioning which includes thinking, remembering and reasoning (1). These losses then manifest in a change of behavior such as the inability to communicate, change in personality, and eventually the loss of self-management. Dementia results when healthy neurons in the brain stop working, lose connections with other neurons, and die (1). While everyone experiences neuron loss as they age, people with dementia experience a loss that is far greater and more progressive. Dementia is a symptom in many neurodegenerative disorders and up to half of all people 85 or older have  some form of dementia. However, it is important to note that dementia is not a normal part of aging (1). Currently, there are no treatments that can cure dementia or the diseases that it accompanies (2). 

Although there have been huge investments made in curing dementia, finding ways to prevent it is just as important. Controllable risk factors include smoking, depression and diabetes (3). Another potential modifiable risk factor is the use of anticholinergic drugs. Anticholinergic drugs are a class of drugs that act by blocking the neurotransmitter acetylcholine in the central and peripheral nervous systems (3). Drugs in this group are very common and treat a range of conditions such as allergies, depression, and bladder issues. It has previously been documented that short-term use of anticholinergic drugs may cause confusion and memory loss in older patients (4). However, the long-term effects of anticholinergic drugs were not examined until now. 

In a recent case study conducted by researchers at the University of Nottingham, it was found that there was a statistically significant association between patients diagnosed with dementia and their exposure to anticholinergic antidepressants (3). This new study analyzed the medical histories of 58,769 patients 55 years or older diagnosed with dementia (3). More specifically, researchers looked at their exposure to anticholinergic drugs over a 20-year history (3). Their drug history was then matched with 56 prescription drugs with strong anticholinergic properties to calculate their drug exposure. Each experimental patient was matched with one or more controls to evaluate whether long exposure did indeed increase risk for dementia (3). 

After normalization, it was found that there were statistically significant associations of dementia risk with exposure to anticholinergic antidepressants, antiparkinson drugs, antipsychotic drugs, bladder antimuscarinics and antiepileptic drugs (3). However, there were no significant increases in risk associated with anticholinergic antihistamines, skeletal muscle relaxants, gastrointestinal antispasmodics, antiarrhythmics or antimuscarinic bronchodilators (3). It was also found that risk was increased nearly 50% when a daily single strong anticholinergic drug was taken for 3 years (3). The link between anticholinergic drugs and dementia was stronger for people diagnosed with dementia before they turned 80 than people diagnosed with Alzheimer’s disease. 

Although there is a statistically significant correlation between anticholinergic drugs and risk of dementia, this study is limited in that there is no way to confirm if the medications played a direct role in causing dementia (3). Nevertheless, this study highlights the importance of reducing risk factors that could significantly increase an individual’s chance of developing dementia. Moreover, clinicians may consider reducing exposure to anticholinergic drugs in middle-aged and older people if possible. Potential risk for dementia should be included when evaluating the adverse effects and benefits when prescribing a drug.

 

References:

  1. What is dementia? Symptoms, types, and diagnosis. National Institute on Aging, (2017). 
  2. What is dementia? Alzheimer’s Association
  3. C. A. C. Coupland, et al., Anticholinergic drug exposure and the risk of dementia a nested case-control study. JAMA International Medicine (2019). doi: 10.1001/jamainternmed.2019.0677.
  4. C. Fox, et al., Anticholinergic medication use and cognitive impairment in the older population: the medical research council cognitive function and ageing study. Journal of the American Geriatrics Society 59 (2011). doi: 10.1111/j.1532-5415.2011.03491.x.
  5. Image retrieved from: https://www.maxpixel.net/Capsule-Bless-You-Pain-Pill-Drugs-Disease-3096637
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