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Medication Adherence: Its Importance in Cardiovascular Outcomes

Disclosure: Honoraria: Preventive Cardiovascular Nurses Association, Association of Women's Health, Obstetric, and Neonatal Nurses, Nexcura; Royalties: UpToDate. 
Pub Date: Monday, August 31, 2009 
Authors: Lynne Braun, PhD, RN  
Article:  Medication Adherence: Its Importance in Cardiovascular Outcomes 


  1. Ho PM, Bryson CL, Rumsfeld JS, ,  Medication adherence: its importance in cardiovascular outcomes.,  Circulation,  119 (23) 3028-35. View in PubMed

Clinical Question

Medication adherence is defined as the "active, voluntary, and collaborative involvement of the patient in a mutually acceptable course of behavior to produce a therapeutic result." This definition assumes that providers partner with their patients to establish a course of treatment that is mutually acceptable to both parties. Medication adherence typically includes two facets: (a) whether patients take their medications as prescribed (one tablet daily); and (b) whether patients continue to take a prescribed medication.

Medication nonadherence is of great concern to clinicians, health-care systems, and other stakeholders (payers) because studies show that nonadherence is highly prevalent and is associated with adverse clinical outcomes and higher costs of care. The need for improved medication adherence is underscored by the rise in performance measures that reward quality based on the achievement of treatment goals.

Assessing patient medication adherence is rare in most clinical practices, yet medication adherence is an important component of cardiovascular outcomes research. In this timely review article, Ho, Bryson, and Rumsfeld address the following: (a) methods of measuring adherence, (b) prevalence of nonadherence, (c) association between nonadherence and outcomes, (d) reasons for nonadherence, and (e) interventions to improve medication adherence.


Methods of Assessing Medication Adherence

Direct methods include directly observed therapy, measurement of medication level or metabolite in blood, and measurement of a biologic marker in blood. These methods are impractical for routine clinical use. Indirect methods include patient questionnaires, other forms of self-report, pill counts, rate of prescription refills, assessment of patient's clinical response, electronic medication monitors, measurement of physiological markers, and patient diaries. Most commonly, patient self-report, pill counts, and pharmacy refills are used as indirect measures of medication adherence. The Morisky scale is a four-item adherence measure that has been shown to predict adherence to cardiovascular mediations. The response to a single question ("In the past month, how often did you take your medications as the doctor prescribed?") was associated with adverse cardiovascular events. Limitations of self-report measures include inaccurate patient recall and the patient's desire to be accepted by the clinician, thus reporting an overestimation of adherence. Pill counts are frequently used in research although they do not accurately reflect the timing of medication-taking and can be manipulated by patients. Electronic pharmacy data are more widely available and have been correlated with several medical outcomes; however, this method assumes that patients obtain their medications from a single pharmacy system.

Prevalence of Medication Nonadherence

Medication nonadherence is common for patients with cardiovascular diseases and risk factors. Studies have shown that almost 25% of post-myocardial infarction (MI) patients didn't fill their prescriptions by day 7 of discharge, one-third of patients stopped at least one medication, and 12% stopped three medications within 1 month of hospital discharge. In general, consistent use of cardiac medications is low. Following diagnosis of coronary artery disease, adherence to aspirin use was the highest during 6 to 12 months follow-up; however, adherence to beta-blockers and lipid-lowering agents was less than 50%. One study found that half of hypertensive patients stopped taking their medications within 1 year, yet another study observed that 75% of patients on monotherapy for hypertension were adherent. Among heart failure patients, adherence rates varied according to the medication evaluated and the method of assessment of medication use.

Association between Medication Adherence and Outcomes

Observational studies evaluating the association between mediation adherence and outcomes have focused on medications previously demonstrated in randomized controlled trials to be efficacious in reducing adverse clinical outcomes. Pharmacy refill data and patient self-report are the most common methods of assessing adherence in these studies. High adherence is typically defined as medication possession ratio of 80% to 100%. In general, nonadherence to cardiovascular medications has been associated with increased risk of morbidity and mortality.

Patterns and Reasons for Medication Nonadherence

Nonadherence may be intentional, an active process whereby a patient makes a choice not to take his medication, or unintentional, a passive process in which a patient is careless or forgetful about taking medication as prescribed. Most medication nonadherence is due to omissions of doses or delays in taking doses.

The World Health Organization has published five categories of non-adherence:

1. Patient factors--physical impairments (e.g., visual problems, impaired dexterity, cognitive impairment, psychological/behavioral issues, younger age, nonwhite race)

2. Conditions that are asymptomatic and chronic in nature, mental health disorders

3. Therapy-related factors (e.g., complexity of regimen, side effects)

4. Socioeconomic factors (e.g., low literacy, higher medication costs, poor social support)

5. Health system problems--poor provider-patient relationship, poor communication, lack of access to care, lack of continuity of care

Interventions to Improve Medication Adherence

In general, unimodal interventions have been less successful than multimodal interventions in improving medication adherence and outcomes. Unimodal interventions include reducing the number of daily medication doses, motivational strategies, packaging medications into special containers (pill boxes, blister packs), providing more convenient care, educating patients, monitoring, and feedback methods. Multimodal interventions used in randomized studies include telemonitoring with voice response technology plus weekly nurse feedback, or a combination of patient education, medication reminder packaging, and frequent clinic visits. A common theme of successful interventions is regular follow-up with the health-care system. 

Clinical Implication/Application

Additional research is needed to develop and test interventions to improve medication adherence that can be practically applied to the clinical setting. Successful interventions to date have multiple components and require clinical personnel for implementation and coordination, which greatly increases the time involved as well as cost. In addition, because our health-care system lacks integration and often patients have multiple health-care providers, logistical challenges prevent the coordination of any intervention.

Because medication nonadherence is strongly associated with poor clinical outcomes, it's imperative that health-care providers assess for nonadherence at every clinic visit. At the least, a simple screening question should be asked (e.g., "During the past 2 weeks, what percent of days have you taken your medications as prescribed?"). Depending on the patient's response to this initial question, the clinician can further inquire about adherence to specific medications, reasons for nonadherence, etc. For health-care systems where pharmacy records are readily available, the clinician can also review refill frequency and the date of the last refill to assist in identifying nonadherence. To prevent and treat nonadherence, clinicians must find a mechanism for improved patient education and create a partnership with patients so that they feel actively involved in their care. Nurses can be used to educate patients about their medications and provide telephone follow-up to ensure that patients are taking medications as directed and to answer any questions patients may have.

Patients often don't understand that taking medication is a form of prevention, particularly for cardiovascular disease. A great deal of explanation may be required to help patients understand that medications for hypertension and lipid abnormalities prevent heart attacks, strokes, and deaths from cardiovascular disease. Furthermore, a discussion of the genetic contribution to risk factors is often useful. Most clinicians find that spending the time to achieve good patient understanding of the rationale for medication use fosters a partnership with patients and improves medication adherence. 

-- The opinions expressed in this commentary are not necessarily those of the editors or of the American Heart Association.