Background: People living with multimorbidity may hold complex beliefs about medicines, potentially influencing adherence. Polynomial regression offers a novel approach to examining the multidimensional relationship between medication beliefs and adherence, overcoming limitations associated with difference scores.
Purpose: To explore the multidimensional relationship between medication beliefs and adherence among people living with multimorbidity.
Methods: Secondary analysis was conducted using observational data from a cohort of older adults living with ≥2 chronic conditions, recruited from 15 family practices in Ireland in 2010 (n = 812) and followed up in 2012 (n = 515). Medication beliefs were measured with the Beliefs about Medicines Questionnaire-Specific. Adherence was assessed with the medication possession ratio using prescription data from the national primary care reimbursement service. Polynomial regression was used to explore the best-fitting multidimensional models for the relationship between (i) beliefs and adherence at baseline, and (ii) beliefs at baseline and adherence at follow-up.
Results: Confirmatory polynomial regression rejected the difference-score model, and exploratory polynomial regression indicated quadratic models for both analyses. Reciprocal effects were present in both analyses (slope [Analysis 1]: β = 0.08, p = .007; slope [Analysis 2]: β = 0.07, p = .044), indicating that adherence was higher when necessity beliefs were high and concern beliefs were low. Nonreciprocal effects were also present in both analyses (slope [Analysis 1]: β = 0.05, p = .006; slope [Analysis 2]: β = 0.04, p = .043), indicating that adherence was higher when both necessity and concern beliefs were high.
Conclusions: Among people living with multimorbidity, there is evidence that the relationship between medication beliefs and adherence is multidimensional. Attempts to support adherence should consider the combined role of necessity and concern beliefs.
Keywords: Beliefs about medicines; Medication adherence; Multimorbidity; Necessity-Concerns Framework; Polynomial regression.
When people live with multiple ongoing health conditions, they might have complex beliefs about their prescribed medicines. These beliefs could relate to the perceived necessity of medicines (necessity beliefs) and perceived concerns about medicines (concern beliefs). This study aimed to explore how necessity and concern beliefs, in combination, relate to the extent to which people living with multiple ongoing conditions take their medicines as prescribed. The study analyzed an existing dataset that included 812 older adults recruited via family practice settings in Ireland in 2010. Of these, 515 people were followed up again in 2012. All participants were living with at least two ongoing health conditions. Participants self-reported their medication-related necessity and concern beliefs by completing a questionnaire. Their level of medication taking was calculated using pharmacy records. The results showed that having a combination of high necessity beliefs and low concern beliefs was related to higher levels of medication taking than having a combination of low necessity beliefs and high concern beliefs. Having a combination of high necessity beliefs and high concern beliefs was related to higher levels of medication taking than having a combination of low necessity beliefs and low concern beliefs. Attempts to support patients to take their medicines should consider the combined role of their necessity and concern beliefs on behavior.
© The Author(s) 2023. Published by Oxford University Press on behalf of the Society of Behavioral Medicine.