Understanding the anticholinergic effect
The Anticholinergic Cognitive Burden Scale
Effectiveness of anticholinergic burden scales
References
Further reading

The Anticholinergic Drug Scale (ADS), developed by Boustani et al., was created to address the issue of anticholinergic burden. This term refers to the cumulative effect of using multiple medications with anticholinergic activity concurrently. This scale has been validated against serum anticholinergic activity (SAA), showing that high SAA levels correlate with cognitive impairments. Moreover, the scale serves to identify drugs with significant anticholinergic activity.

Understanding the anticholinergic effect

The anticholinergic burden represents the cumulative impact of taking one or more medications that inhibit cholinergic activity. Anticholinergic drugs work by preventing the neurotransmitter acetylcholine from binding to muscarinic receptors, resulting in anticholinergic effects. These effects can be desirable in certain situations, such as with antipsychotics, antidepressants, and analgesics.

Anticholinergic effects on peripheral function include dry mouth, blurred vision, constipation, urinary retention, and an elevated heart rate. Central effects may lead to sedation, confusion, dizziness, and, in some cases, cognitive impairment. The likelihood of experiencing these side effects increases when multiple medications with anticholinergic properties are used concurrently.

The anticholinergic burden is a strong indicator of cognitive and physical impairment, especially in aging populations, where it has been linked to a higher rate of falls, memory decline, difficulties in performing daily activities, and increased mortality. Given the growing prevalence of polypharmacy, it is expected that the use of anticholinergic medications will continue to rise.

The Anticholinergic Cognitive Burden Scale

The Anticholinergic Cognitive Burden Scale is derived from a comprehensive literature review of medications that possess anticholinergic activity. This scale categorizes drugs based on their potential negative impact on cognition, ranging from zero (no anticholinergic activity) to possible and finally to definite anticholinergic activity, with scores ranging from zero to three. The Anticholinergic Cognitive Burden Scale identifies 88 medicines with known anticholinergic activity.

Similar methodologies have been used to develop other anticholinergic risk scales in countries like Germany, Australia, France, and the United States. For instance, the CrAC scale developed by Han et al. was designed for use in veteran homes and palliative care settings, primarily for evaluating functional and cognitive outcomes. Meanwhile, the anticholinergic activity scale developed by Ehrt et al. and the anticholinergic loading scale by Sittironnarit et al. were created specifically to assess cognitive outcomes.

Effectiveness of anticholinergic burden scales

A systematic review was conducted to assess the effectiveness of anticholinergic burden scales in predicting adverse outcomes in older individuals. This is particularly relevant as the anticholinergic burden has been associated with negative outcomes in aging populations.

The study involved a comprehensive literature search in Ovid Medline, Embase, and Psychinfo from 1984 to 2014 to identify anticholinergic risk scales developed through expert opinion. Individual scales were assessed by analyzing Web of Science and Google Scholar to track references cited in selected articles. The primary outcomes of interest included functional and cognitive outcomes associated with anticholinergic burden in older individuals.

The results revealed a total of 1,250 records across the three databases. The review identified seven expert-based anticholinergic rating scales that met the inclusion criteria. Among these, one scale rated certain anticholinergic medications as having high anticholinergic activity, one as moderate, and two as low.

Consequently, the study concluded that there is no standardized tool available for measuring anticholinergic burden accurately. Additionally, cohort studies have consistently shown that a higher anticholinergic burden is associated with adverse effects on the brain, including poorer functional and cognitive outcomes.

The study also recognized the need for a reference composite scale that could assist healthcare professionals in more precisely identifying anticholinergic medicines. In another study comparing six anticholinergic scales, including the Anticholinergic Drug Scale (ADS) and Anticholinergic Cognitive Burden (ACB) scale, researchers found that ADS and ACB were suitable for use in observational studies requiring quantification of anticholinergic exposure.

These scales considered various medications and were validated using adverse clinical outcomes. Moreover, they were developed for general populations and applied successfully to administrative data. The research team highlighted the need to develop and validate longitudinal study methodologies that encompass both aspects of anticholinergic treatment.

References

• Ehrt U, Broich K, Larsen JP, et al. (2010) Use of drugs with anticholinergic effect and impact on cognition in Parkinson's disease: a cohort study. J Neurol Neurosurg Psychiatry. doi: 10.1136/jnnp.2009.186239.
• Ancelin ML, Artero S, Portet F, et al (2006) Non-degenerative mild cognitive impairment in elderly people and use of anticholinergic drugs: longitudinal cohort study. BMJ. doi: 10.1136/bmj.38740.439664.DE. 
• Boustani M, Campbell N, Munger S, et al. (2008) Impact of anticholinergics on the aging brain: A review and practical application. Future Medicine. doi: 10.2217/1745509X.4.3.311
• Carnahan RM, Lund BC, Perry PJ, ET AL. (2006) The Anticholinergic Drug Scale as a measure of drug-related anticholinergic burden: associations with serum anticholinergic activity. J Clin Pharmacol. doi: 10.1177/0091270006292126.
• Sittironnarit G, Ames D, Bush AI, ET AL. (2011) Effects of anticholinergic drugs on cognitive function in older Australians: results from the AIBL study. Dement Geriatr Cogn Disord. doi: 10.1159/000325171.
• Rudolph JL, Salow MJ, Angelini MC, ET AL (2008). The anticholinergic risk scale and anticholinergic adverse effects in older persons. Arch Intern Med. doi: 10.1001/archinternmed.2007.106.
• Salahudeen MS, Duffull SB, Nishtala PS. (2015) Anticholinergic burden quantified by anticholinergic risk scales and adverse outcomes in older people: a systematic review. BMC Geriatr. doi: 10.1186/s12877-015-0029-9.

Further Reading

• All Cognitive Function Content
• What is Executive Functioning?
• What is Mild Cognitive Impairment?
• What is Post-Operative Cognitive Decline?

Written by

Hidaya Aliouche

Hidaya is a science communications enthusiast who has recently graduated and is embarking on a career in the science and medical copywriting. She has a B.Sc. in Biochemistry from The University of Manchester. She is passionate about writing and is particularly interested in microbiology, immunology, and biochemistry.