Assessing the multidimensional relationship between medication beliefs and adherence in older adults with hypertension using polynomial regression.

Dillon, Paul; Phillips, L. Alison; Gallagher, Paul; Smith, Susan M.; Stewart, Derek; Cousins, Gr�inne

Abstract

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). The purpose of this study was to assess the multidimensional effect of patient medication beliefs (concerns and necessity beliefs) on medication adherence using polynomial regression with response surface analysis. Community-dwelling older adults over 65 years old (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. 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 < 0.001; curvature β = -0.26, p = 0.004). 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 = 0.004; curvature β = -0.25, p = 0.003). The difference-score model fails to account for the potential nonreciprocal effects. The results therefore extend evidence supporting the use of polynomial regression to assess the multidimensional effect of medication beliefs on adherence.

Citation

DILLON, P., PHILLIPS, L.A., GALLAGHER, P., SMITH, S.M., STEWART, D., COUSINS, G. 2018. Assessing the multidimensional relationship between medication beliefs and adherence in older adults with hypertension using polynomial regression. Annals of behavioral medicine [online], 52(2), pages 146-156. Available from: https://doi.org/10.1093/abm/kax016

• Journal Article Type: Article
• Acceptance Date: Jan 11, 2018
• Online Publication Date: Jan 11, 2018
• Publication Date: Feb 28, 2018
• Deposit Date: Jan 15, 2018
• Publicly Available Date: Jan 12, 2019
• Journal: Annals of behavioral medicine
• Print ISSN: 0883-6612
• Electronic ISSN: 1532-4796
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 52
• Issue: 2
• Pages: 146-156
• DOI: https://doi.org/10.1093/abm/kax016
• Keywords: Beliefs about Medicines Questionnaire (BMQ); Medication adherence; Necessity concerns framework; Polynominal regression
• Public URL: http://hdl.handle.net/10059/2657