Kjeldsen, L.J., Bjerrum, L., Herborg, H. et al. Int J Clin Pharm (2011) 33: 565. doi:10.1007/s11096-011-9509-y
Objective To identify various types of non-adherence among users of antihypertensive medications by establishing components of adherence measures and use these components for measuring the prevalence of non-adherence. Setting Twelve community pharmacies from the Danish county of Funen. Method Users of antihypertensive medication were included in the study. 2,914 medication users received questionnaires by mail. Participating patients were asked to fill in two questionnaire regarding demographics, self-reported blood pressure, and various adherence measures. Two factor analyses were conducted based on responses to questions. Main outcome measures Medication-taking behaviour and self-efficacy (beliefs about ability and capacity to accomplish a task), respectively. Other measures of non-adherence collected by questionnaire were also addressed in the data for comparison of prevalence with the developed concepts. Results 1,426 (49%) participants answered the questionnaires. The analyses resulted in two sets of components: three adherence behaviour measures and two self-efficacy measures which showed similarities in concepts. The adherence behaviour measures included two concepts of intentional nonadherence (associated with aspects of self-regulation and effect concerns, respectively) and one measure of non-intentional non-adherence. Prevalence of the developed measures of behaviour related non-adherence ranged from 10.3 to 34.9% depending on which type of non-adherence measure was used. Established measures of non-adherence resulted in prevalence between 2.2 and 39.6%. Conclusions The study showed that concepts of non-adherence measurements could be determined including self-efficacy aspects, unintentional non-adherence and intentional non-adherence related to self-regulation and effect concerns respectively. The prevalence of the adherence behaviour components were found to be between 10.3 and 34.9%, which is in the range of expected values. Associations between the new concepts of non-adherence measurement and characteristics of nonadherers remain to be established and would be a subject for further studies.