Improving adherence with medication: a selective literature review based on the example of hypertension treatment.

The term “compliance,” which was used most often in the past, is often understood from a perspective of a paternalistic or maternalistic role of the treating health professional, in the sense of not following the drug regimen prescribed by the doctor. The term “adherence,” which is the preferred term today, is based on the therapeutic alliance between patient and treating physician and thus explicitly refers to responsibilities on both sides. The concept of shared decision making can be considered as accepted in this setting (Box 1) (1, e1– e3). It is also consistent with the definition of adherence as proposed by the World Health Organization (WHO): “The extent to which a person’s behavior—taking medication, following a diet, and/or executing lifestyle changes, corresponds with agreed recommendations from a health care provider” (2). Adherence in the wider sense describes the extent to which a patient follows a treatment plan. In industrialized countries, medication adherence for chronic diseases is often only around 50% (2). The forms and patterns of adherence (or non-adherence) with medication and the parameters for measuring these are varied. The measure used most often is determining the proportion of drug doses that are prescribed and then actually taken. According to Dunbar, adherence and its measurement can be placed in one of three categories (3). The first category is that of the quantity of medication, and further differentiation comes under that category—for example, between the proportion of medical drugs taken relative to the doses laid out in the treatment plan (the prescribed doses), the proportion of medications taken in the correct dosage, or the taking of the medication doses at the time stipulated in the treatment plan (4– 6). The term “persistence” describes the proportion of patients who (still) follow the prescribed drug treatment at all, or “the duration of time from initiation to discontinuation of therapy” (4, 5). Depending on the observation period, it is difficult to distinguish between non-persistence and temporary drug holidays. Relative to the overall prevalence of non-persistence, primary non-persistence—that is, a situation in which a prescribed medication regimen is not even started—represents a lower proportion of patients, at 5%, but still a relevant proportion (4, e4– e6). Dunbar’s second category attempts a qualitative evaluation of adherence as “good” or “poor” (non-adherence) (3). However, the definition of what is considered “good” adherence varies notably in different studies—for example, with threshold values of = 80% to = 95% regarding the ingestion of prescribed doses (6). The third category comprises combined adherence indices that associate different behaviors (for example, taking medication, turning up for doctor’s appointments, abstaining from nicotine) and/or awareness/knowledge (for example, about the treatment or disorder). Box 1 Shared decision making in the therapeutic setting (1) The interaction between doctor and patient aims to identify the appropriate therapy by reaching a decision jointly by means of communication This entails explaining the current scientific evidence on the background of a doctor–patient partnership orientation. The best possible decision about therapy should be reached according to clinical demands and by recognizing the patient’s preferences. Studies have shown that low adherence is associated with a reduction or total absence of therapeutic success, reduced quality of life, and higher treatment costs, among others; good adherence, by contrast, is associated with lower mortality in clinical studies (2, 7, 8). Many studies have been conducted of the question of which factors can influence adherence with medication and of which measures can increase compliance with regard to medication therapy (2, 6, 9, e7– e10). In this article, we provide an overview of studies that investigated whether measures to promote adherence influenced compliance on the one hand and clinical end points on the other hand. Our focus was on studies of arterial hypertension, since hypertension is a clinically relevant example of a common disorder with serious consequences, which can be treated effectively, but whose therapy in all experience has been associated with unsatisfactory adherence (2, 10, e11, e12).