Antihypertensive medication adherence in cancer survivors and its affecting factors: Results of a Korean population-based study

Purpose: Cancer survivors have been reported to receive less care for other conditions than the general population; however, it is not clear whether patients' behavior also contribute to this. The present study was performed to examine cancer survivors' adherence to antihypertensive medication and factors associated with it, compared to the general population. Methods: We used pharmacy claims and enrollment data from the National Health Insurance, which covers 97% of the Korean population. In total, 2,455,193 subjects, including 12,636 (0.5%) cancer survivors, who were prescribed antihypertensive medications during the calendar year 2004 were identified. A cumulative medication adherence of 80% or above was defined as appropriate medication adherence. Two separate multiple logistic regressions were developed to compare the proportion of appropriate adherence between two populations and to identify factors affecting medication adherence in cancer survivors. Results: Cancer survivors were less likely to have an appropriate medication adherence than the general population (adjusted odds ratio = 0.85; 95% CI, 0.82-0.88). Significant variation was observed in medication adherence according to cancer type. Several other factors, such as older age, low income, living in a rural area, and antihypertensive medication duration, also affected antihypertensive medication adherence. Contrary to the general population, younger survivors showed higher adherence. Conclusions: Clinicians involved in survivor care should check patient adherence to antihypertensive medication, as well as assess the possible reasons for nonadherence. Further studies are warranted to determine the reasons for nonadherence and to establish effective interventions in this vulnerable population.