Polypharmacy and Excessive Polypharmacy Among Persons Living with Chronic Pain: A Cross-Sectional Study on the Prevalence and Associated Factors

Abstract

Purpose

Polypharmacy can be defined as the concomitant use of ≥5 medications and excessive polypharmacy, as the use of ≥10 medications. Objectives were to (1) assess the prevalence of polypharmacy and excessive polypharmacy among persons living with chronic pain, and (2) identify sociodemographic and clinical factors associated with excessive polypharmacy.

Patients and Methods

This cross-sectional study used data from 1342 persons from the ChrOnic Pain trEatment (COPE) Cohort (Quebec, Canada). The self-reported number of medications currently used by participants (regardless of whether they were prescribed or taken over-the-counter, or were used for treating pain or other health issues) was categorized to assess polypharmacy and excessive polypharmacy.

Results

Participants reported using an average of 6 medications (median: 5). The prevalence of polypharmacy was 71.4% (95% CI: 69.0–73.8) and excessive polypharmacy was 25.9% (95% CI: 23.6–28.3). No significant differences were found across gender identity groups. Multivariable logistic regression revealed that factors associated with greater chances of reporting excessive polypharmacy (vs <10 medications) included being born in Canada, using prescribed pain medications, and reporting greater pain intensity (0–10) or pain relief from currently used pain treatments (0–100%). Factors associated with lower chances of excessive polypharmacy were using physical and psychological pain treatments, reporting better general health/physical functioning, considering pain to be terrible/feeling like it will never get better, and being employed.

Conclusion

Polypharmacy is the rule rather than the exception among persons living with chronic pain. Close monitoring and evaluation of the different medications used are important for all persons, especially those with limited access to care.

Keywords:

• chronic pain
• polypharmacy
• excessive polypharmacy
• prevalence
• associated factors
• determinants

Abbreviations

CP, Chronic pain; US, United States; COPE, ChrOnic Pain trEatment; IMMPACT, Initiative on Methods, Measurement, and Assessment of Pain in Clinical Trials; SPOR CPN, Strategy for Patient-Oriented Research Chronic Pain Network; BSRI, Bem Sex Role Inventory; BPI, Brief Pain Inventory; DN4, Douleur Neuropathique 4; NRS, Numeric rating scale; PHQ-4, 4-item Patient Health Questionnaire; SF-12, 12-Item Short Form Survey.

Data Sharing Statement

The Cope Cohort dataset is not readily available because participants did not initially provide consent to open data. The data that support the findings of this study are available from the corresponding author upon reasonable request and conditionally to a proper ethical approval for a secondary data analysis. Programming codes can be obtained directly from the corresponding author.

Ethics Approval and Informed Consent

Ethical approval was provided by the Université du Québec in Abitibi-Témiscamingue’s research ethics committee (#2018-05-Lacasse, A.). All participants provided free and informed consent. Our study complies with the Tri-Council Policy Statement and the Declaration of Helsinki.

Acknowledgments

We would like to thank the study participants for their contribution to the research, and Ms. Véronique Gagnon, who was involved in the implementation, data cleaning and data management of the COPE Cohort. Special thanks to Ms. Geneviève Lavigne who provided assistance for scientific writing and English language editing.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

In part of her Masters’ degree training, GZ (first author) received scholarships from the Fondation de l’Université du Québec en Abitibi-Témiscamingue (FUQAT) in partnership with the Pharmacie Jean-Coutu de Rouyn-Noranda (community pharmacy) and travel awards from the Quebec Pain Research Network (QPRN). At the time the study was conducted, AL held a Junior 2 research scholarship from the FRQS in partnership with the Quebec SUPPORT Unit (Support for People and Patient-Oriented Research and Trials) and MGP a Junior 1 research scholarship from the FRQS. The Chronic Pain Epidemiology Laboratory led by AL is funded by the FUQAT, in partnership with local businesses: the Pharmacie Jean-Coutu de Rouyn-Noranda and Glencore Fonderie Horne (copper smelter). LB received research grants from AstraZeneca, TEVA and Genentech, as well as consultation fees from AstraZeneca, TEVA and Genentech for projects unrelated to this study. MGP received honoraria from Canopy Growth and research funds from Pfizer Canada for projects unrelated to this study. The authors report no other conflicts of interest in this work.

Additional information

Funding

The implementation of the COPE Cohort was supported by the Quebec Network on Drug Research and the exploitation of its data was co-funded by the Quebec Pain Research Network, two thematic networks of the Fonds de recherche du Québec – Santé (FRQS).