To the Editor
Low medication adherence is a main limitation of the long-term effectiveness of treatment in patients with chronic diseases [1–3]. Low adherence is recognized as a serious health problem particularly in elderly patients due to the presence of numerous comorbidities and concomitant polypharmacy [4–6]. There are multiple patient-related causes leading to poor adherence associated with old age, including decreased quality of life, low mood and presence of depressive symptoms, and clinical and sociodemographic factors. Recently Pobrotyn et al. published in the Medical Research Journal the results of a prospective cross-sectional study assessing adherence problems in 100 elderly patients with hypertension [7]. They observed a relatively high proportion of patients with a high level of adherence (63%) and a very low incidence of low adherence (3%) as assessed with the Adherence in Chronic Disease Scale (ACDS). The authors observed a negative correlation indicating that more severe depressive symptoms were associated with poorer adherence while a higher quality of life was associated with better adherence. A higher level of adherence was also observed in patients with higher education and better economic status. Nevertheless, none of these variables was an independent predictor of the adherence level assessed with the ACDS. However, it should be emphasized that the ACDS allows to assess the risk of non-adherence, but not adherence itself [8–11]. No objective, direct method of a patient’s medication-taking behaviour assessment was used to verify the results obtained with this self-reported questionnaire [2]. We are proud and grateful to the authors that they decided to use the diagnostic tool developed by us, however, we feel obliged to point out its limitations. The search for methods of adherence assessment that are both effective and easy to apply remains a great challenge [12–15].