gms | German Medical Science

Adherence describes the extent to which a therapy actually is put into practice. Insufficient adherence (i.e. non-adherence) has been known for a long time. Different taxonomy and wording (e.g. compliance versus adherence) indicate a continuing change of definition and interpretation. There is broad consensus that adherence often is not satisfying. Many studies show that only 50-60% of patients can be judged as adherent (mostly: taking at least 80% of prescribed drug doses). This is true for very different drug classes that already have proven to be beneficial (e.g. bisphosphonates in osteoporosis or statins in cardiovascular prevention). Non-adherence can affect the course of disease. It has been shown that adherence is associated with the risk of hospitalisation, effects on accepted surrogate parameters (e.g. blood pressure or HbA1c) and even mortality. Many heterogeneous measures have been shown to improve adherence. Though there is neither a gold standard nor a consensus regarding essential elements of those interventions, it is intriguing that already simple measures can be effective (e.g. reduction of drug doses). On the other hand, many studies suggest that one often will not succeed in improving adherence. Nonetheless, it has been shown that a successful improvement of adherence is often associated with beneficial effects regarding clinical endpoints. Adverse effects of adherence facilitating measures are not known.

In summary, adherence is an important factor regarding effectiveness and efficiency of drug treatment. The ongoing challenge will be to identify measures that are effective and feasible to improve adherence in an individual patient. Adherence should already be considered, e.g. in physician-patient communication or development of treatment plans.