Predicting medication adherence: testing the health action process approach at the inter- and intrapersonal level

Abstract

Background: More than 50 % of people over 60 years of age have two or more co-occurring diseases, and are thus multimorbid. As a result, these individuals often have to adhere to complex polypharmacy therapies whereby non-adherence to the prescribed medication is a known problem. The Health Action Process Approach (HAPA) has been applied successfully for various health behaviors. This study aimed at testing the HAPA at the inter- and intrapersonal level in the context of medication adherence. Methods: N=83 (n = 37 men; Mage = 61.8, SD = 13.3) multimorbid individuals completed thirty diaries reporting their daily medication adherence and HAPA variables. Multilevel models tested the assumptions made by the HAPA at the intra- and interpersonal level. Findings: Overall, participants reported high intentions to adhere to their medication and high medication adherence. However, 50% of participants reported at least one non-adherent event. On days with more than usual self-efficacy higher intention was reported. Moreover, individuals reported higher levels of medication adherence on days with higher than usual action control. Additionally, interpersonal differences in self-efficacy and action control were significantly positively associated with medication adherence. Planning was negatively associated with medication adherence at both levels but causal direction remains unclear. Discussion: These findings partially confirm the assumptions of the HAPA in the context of medication adherence at both the inter- and intrapersonal level. Especially self-efficacy and action control show positive effects on medication adherence. Future studies in the context of medication adherence should take care of a heterogeneous sample.