Adherence: How to Measure and Improve It

More than 90% of older adults receive drug prescriptions according to guidelines for specific diseases, and polypharmacy is one of the main determinants of poor adherence to treatment in older patients. Adherence has been defined as the extent to which a person’s behavior—taking medication, following a diet, and/or executing lifestyle changes—corresponds with agreed recommendations from a healthcare provider. When limiting to medication adherence, the latter is usually defined as the proportion of days covered of more than 80%. At present, poor adherence is the main factor underlying the failure of patients and healthcare systems to achieve treatment outcomes. Measuring medication adherence is important to clinicians and researchers, and there is no “one size fits all” approach. The methods used should be tailored to the question being asked and in the specific population and should consider the severity of the consequences of non-adherence. There are many ways to measure medication adherence, and they usually fall into direct (e.g. blood samples) or indirect (e.g. pill count) methods, and subjective (e.g. questionnaires) and objective measures. It is likely that a multi-modal approach encompassing objective and subjective measures will yield the most accurate estimate of adherence. The benefits of proper adherence to treatment are several, including preventing diseases, improvement of health, better quality of life and a more cost-effective use of healthcare resources. To date, no single intervention strategy has proven effectiveness in enhancing adherence across all patients, clinical conditions and settings. The reasons of non-adherence are so multifactorial that interventions to improve it should be patient-centred, involving multiple stakeholders, with the different players providing different services, but integrated with one another.