Journal Article

Assessing the Multidimensional Relationship Between Medication Beliefs and Adherence in Older Adults With Hypertension Using Polynomial Regression

Paul Dillon, L Alison Phillips, Paul Gallagher, Susan M Smith, Derek Stewart and Gráinne Cousins

in Annals of Behavioral Medicine

Volume 52, issue 2, pages 146-156
ISSN: 0883-6612
Published online January 2018 | e-ISSN: 1532-4796 | DOI: http://dx.doi.org/10.1093/abm/kax016

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Abstract

Background

The Necessity–Concerns Framework (NCF) is a multidimensional theory describing the relationship between patients’ positive and negative evaluations of their medication which interplay to influence adherence. Most studies evaluating the NCF have failed to account for the multidimensional nature of the theory, placing the separate dimensions of medication “necessity beliefs” and “concerns” onto a single dimension (e.g., the Beliefs about Medicines Questionnaire–difference score model).

Purpose

To assess the multidimensional effect of patient medication beliefs (concerns and necessity beliefs) on medication adherence using polynomial regression with response surface analysis.

Methods

Community-dwelling older adults >65 years (n = 1,211) presenting their own prescription for antihypertensive medication to 106 community pharmacies in the Republic of Ireland rated their concerns and necessity beliefs to antihypertensive medications at baseline and their adherence to antihypertensive medication at 12 months via structured telephone interview.

Results

Confirmatory polynomial regression found the difference-score model to be inaccurate; subsequent exploratory analysis identified a quadratic model to be the best-fitting polynomial model. Adherence was lowest among those with strong medication concerns and weak necessity beliefs, and adherence was greatest for those with weak concerns and strong necessity beliefs (slope β = −0.77, p<.001; curvature β = −0.26, p = .004). However, novel nonreciprocal effects were also observed; patients with simultaneously high concerns and necessity beliefs had lower adherence than those with simultaneously low concerns and necessity beliefs (slope β = −0.36, p = .004; curvature β = −0.25, p = .003). The difference-score model fails to account for the potential nonreciprocal effects.

Conclusion

Results extend evidence supporting the use of polynomial regression to assess the multidimensional effect of medication beliefs on adherence.

Keywords: Beliefs about Medicines Questionnaire (BMQ); Medication Adherence; Necessity-Concerns Framework; Polynomial Regression

Journal Article.  6939 words.  Illustrated.

Subjects: Medicine and Health ; Patient Education and Information ; Primary Care ; Public Health and Epidemiology

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