Defining Adherence


Medication Adherence: the extent to which a patient’s behavior (e.g. taking medications with respect to timing, dosage, and frequency) corresponds with agreed-upon recommendations from a health-care provider

Medication Compliance: the extent to which a patient passively follows the advice of their provider

Medication Persistence: the duration of time from initiation to discontinuation of therapy

Note: Adherence is measured over a period of time and reported as a percentage, whereas persistence is reported as a continuous variable in terms of number of days for which the therapy was available. It is important to take into consideration both factors as clinical outcomes are affected not only by how well patients take their medications but also by how long they take them.

Medication Nonadherence
Nonadherence may include one or more of the following:
  • Delay or not filling a prescription
  • Not picking up a prescription
  • Skipping doses
  • Splitting pills or stopping a medication early
  • Not refilling a prescription
Factors that Limit Adherence
The World Health Organization defines 5 interacting dimensions of adherence. It is important to note that a patient’s nonadherence is typically due to a combination of factors.
  1. Social and economic factors (e.g. language, literacy, insurance/costs, healthcare facility accessibility, cultural beliefs)
  2. Health care system/HCT (health care team) factors (e.g. long wait times, lack of continuity of care, poor provider-patient relationship, weak education, restricted formularies)
  3. Condition-related factors (e.g. chronic diseases, depression, psychotic disorders, disability, symptoms)
  4. Therapy-related factors (e.g. complexity of regimen, difficult administration techniques, side effects)
  5. Patient-related factors (e.g. physical impairments, lack of motivation, psychosocial stress, anxiety, anger, alcohol or substance abuse)