The term Anticholinergic Burden (ACB) describes the cumulative effect of multiple medications that block the neurotransmitter acetylcholine. Acetylcholine is a major chemical messenger involved in many involuntary body functions. The problem arises because numerous medications, prescribed for various conditions, possess unintended anticholinergic properties, even if they are not explicitly classified as such.
When a person takes several of these drugs simultaneously, the individual anticholinergic effects combine and intensify, leading to a measurable total burden. This cumulative effect is a particular concern for older adults, who are more likely to take multiple medications and whose bodies are naturally more sensitive to these drug effects. Physiological changes associated with aging, such as reduced metabolism and fewer cholinergic neurons, make the geriatric population highly vulnerable to the risks of a high anticholinergic load.
How Anticholinergic Drugs Affect the Body
Anticholinergic drugs exert their influence by blocking acetylcholine receptors throughout the central and peripheral nervous systems. This blockade disrupts the normal signaling pathways essential for the body’s “rest and digest” functions. The immediate, acute effects of this disruption are often felt in peripheral organs, leading to a range of physical symptoms.
Common peripheral side effects include dry mouth, blurred vision, constipation, and urinary retention. These drugs can also cross the blood-brain barrier, affecting the central nervous system and causing acute symptoms like sedation, dizziness, or mild confusion.
Medication classes known to contribute to this burden include some older antihistamines, tricyclic antidepressants, certain antipsychotics, and medications used to treat overactive bladder or Parkinson’s disease. Even drugs not primarily considered anticholinergic, such as some common anti-nausea or muscle relaxant medications, can contribute to the overall effect.
Quantifying the Cumulative Risk
Clinicians quantify cumulative anticholinergic risk using standardized tools that assign a numerical score to a patient’s medication regimen. Scales like the Anticholinergic Cognitive Burden (ACB) scale are frequently employed for this purpose.
These tools assign a score, typically from one to three, to each medication based on its known potency for blocking acetylcholine receptors. A score of one indicates possible anticholinergic activity, while a score of three signifies definite and strong activity. The individual scores for all medications are then summed to produce a patient’s total anticholinergic burden score.
A higher total score correlates directly with an increased risk of adverse health outcomes. For example, a combined ACB score of three or higher is considered significant and is associated with increased cognitive impairment and mortality in older adults. This scoring method allows healthcare providers to assess pharmacological risk objectively and identify patients who would benefit most from a medication review.
Serious Health Outcomes Associated with High Burden
A persistently high anticholinergic burden is linked to long-term health consequences, particularly those affecting the central nervous system. One of the most significant outcomes is an increased risk of cognitive impairment and dementia. Studies have shown that for older adults, moving from a low ACB score to a high score (four or greater) can increase the adjusted odds of incident dementia.
The risk extends beyond chronic cognitive decline to acute brain dysfunction, notably an increased likelihood of acute delirium or severe confusion. This is particularly evident in vulnerable settings, such as during a hospital stay or following an illness or surgery. Delirium, characterized by a sudden change in mental status, often leads to longer hospital stays and poorer recovery outcomes.
Furthermore, a high anticholinergic load significantly increases the risk of falls, fractures, and accidents. The central effects of these medications, including dizziness, reduced coordination, and sedation, impair balance and reaction time. This effect, combined with the vision changes and muscle weakness that can occur, makes individuals with a high burden more susceptible to debilitating injuries.
The chronic use of anticholinergic drugs has also been linked to an increased risk of cardiovascular events and all-cause mortality, showing a linear dose-response relationship between the burden score and the risk. Higher scores are also associated with increased markers of inflammation, suggesting a possible mechanistic pathway for some of these systemic issues.
Steps for Medication Review and Reduction
Managing a high anticholinergic burden requires a systematic and collaborative approach focused on reducing unnecessary medication exposure. This process is often referred to as “deprescribing,” which involves the careful, supervised reduction or discontinuation of medications that may be causing harm or are no longer beneficial. It is important to understand that any changes to a medication regimen should only be made in consultation with a healthcare provider, such as a pharmacist or physician.
The initial step in mitigation involves a comprehensive medication review to identify all drugs contributing to the patient’s total anticholinergic score. Healthcare professionals can then explore substituting high-risk anticholinergic medications with safer, non-anticholinergic alternatives when appropriate. For instance, a different class of antidepressant or a non-drug therapy for urinary incontinence may be considered.
If a medication must be stopped, it is often weaned off gradually to prevent withdrawal symptoms, which can include anxiety, nausea, or sweating. Gradual dose reduction, sometimes by 25% to 50% every few weeks, allows the body time to adjust and minimizes the risk of symptom recurrence. This careful management plan, often involving a multidisciplinary team, can lead to a significant decrease in the anticholinergic score and a reduction in adverse effects like falls and frailty.