Kelly B. Haskard‐Zolnierek and Briana Cobos
Department of Psychology, Texas State University, San Marcos, TX, USA
The primary factor in achieving optimal health and the effectiveness of a medical treatment plan is determined by the patient's adherence toward their treatment regimen. Adherence is defined as the extent to which a patient's behavior corresponds with the agreed‐upon treatment guidelines set forth by a healthcare provider. The terms “compliance” and “persistence” are essentially synonymous with the term “adherence”; however, adherence is preferred because compliance suggests that the patient is passively obeying the guidelines of the medical provider. Persistence describes the degree to which the patient follows the guidelines or behavior modifications recommended by a provider for a predetermined duration of time. Adherence includes various health‐related behaviors such as taking medication, filling prescriptions, attending follow‐up appointments, self‐management of a chronic and/or acute disease, receiving immunizations, and/or modifying one's lifestyle behaviors. These behaviors are intended to provide optimal health when followed.
The terms “adherence” and “concordance” similarly describe a situation in which a treatment plan is negotiated and collectively determined between the patient and physician. The primary objective of concordance is to establish a therapeutic relationship between the patient and physician. However, “adherence” is the preferred term because it suggests an agreement between a patient and a healthcare provider, that is, negotiated, planned, and discussed with a collaborative and therapeutic effort to determine a treatment plan and/or behavior modifications aimed at providing optimal health for the patient.
In contrast, nonadherence constitutes the patient failing to follow the recommended treatment regimen. An individual can be nonadherent by not taking their medication, discontinuing their medications before the recommended time set forth by their healthcare provider, not taking their medication dosage correctly, and/or disregarding certain behavior modifications that are part of the treatment plan. Furthermore, an individual can be nonadherent by not filling a prescription, which is referred to as “nonfulfillment.”
Intentional nonadherence is another form of nonadherence in which an individual actively decides not to follow a healthcare provider's treatment recommendations or guidelines. Within this type of nonadherence, the individual usually takes an active approach in deciding whether to adhere or not adhere to their treatment plan. Individuals' beliefs and knowledge of their health condition and treatment regimen play an important role in their decision. For example, the individual may actively decide to discontinue medication due to aversive symptoms subsiding.
Alternatively, an individual can be unintentionally nonadherent toward treatment. This type of nonadherence can occur when the individual forgets to take a medication or lacks knowledge or understanding about how to take medication or adhere to a treatment plan. This has less to do with the individual's belief or knowledge. Instead, this type of nonadherence is due to unforeseen circumstances, such as the complexity of a treatment plan causing the individual to forget certain behavior modifications or medication dosages. Therefore, nonadherence could ultimately lead the individual to not experience the benefits of their treatment plan and can further worsen an individual's well‐being.
Rates of nonadherence vary depending on regimen, disease, disease category (i.e., acute versus chronic), and other factors. On average, rates of nonadherence range from 25 to 50%, with greater rates of nonadherence in lifestyle change regimens (e.g., making major dietary changes or maintaining a consistent exercise regimen). Rates of nonadherence tend to be higher for more complex regimens such as those that require multiple doses per day or have more complicated dosing instructions, such as associated dietary restrictions. In addition, rates of nonadherence to chronic diseases can be greater due to the long‐term nature of these regimens as compared with adherence to short‐term regimens for acute diseases. A meta‐analysis of 569 studies published from 1948 through 1998 reported the highest rates of adherence in HIV and cancer and the lowest rates in pulmonary diseases, diabetes, and sleep disorders (DiMatteo, 2004a). Other meta‐analytic work has shown that across 116 studies, patients with serious illnesses such as end‐stage renal disease or heart disease who are in poorer health (either objectively or according to self‐ratings) are less adherent (DiMatteo, Haskard, & Williams, 2007). These variations in rates of adherence across diseases could be due to the complex nature of some disease regimens, other factors such as adverse side effects, and other restrictions on one's activities and lifestyle. This nonadherence could also be due to personal factors such as depression, cognitive deficits, and pessimism that can accompany serious illnesses.
There are various causes of nonadherence to treatment regimens. For example, contributing factors toward nonadherence can include the following: adverse medication side effects, a long duration of treatment, frequency of expected intake of medication, or the complexity of the treatment. Nonadherence is an important healthcare issue because of the associated financial, health, and other consequences. Patients who are nonadherent are more likely to utilize healthcare resources, thus increasing healthcare costs.
The economic burden of nonadherence in the United States is estimated to be between $290 and $300 billion dollars each year. This burden is caused by individuals who are unable to modify health or lifestyle behaviors, patients unable to attend medical visits, secondary illnesses that arise due to uncontrolled chronic health conditions, and unnecessary hospitalizations or emergency room visits because of uncontrolled health conditions (DiMatteo, Haskard Zolnierek, & Martin, 2012). Nonadherence could also cause either additional economic burden in the US workforce by loss of productivity at work or an increased rate of employee absenteeism. Nonadherence has been associated with higher costs in various diseases, wherein patients face greater annual healthcare costs because of their nonadherence (Iuga & McGuire, 2014).
Conversely, increased rates of adherence provide economic benefits. An increase in adherence rates would reduce the use and cost of healthcare resources needed during relapses, emergencies, and/or hospitalizations that could have been prevented by the patient following their treatment regimen. Therefore, nonadherence represents a serious issue for healthcare professionals, patients, and the healthcare industry, in which optimal health outcomes are exclusively determined by the individual's adherence toward a treatment regimen.
Nonadherence toward a treatment regimen can have further adverse effects on an individual's health outcomes by causing additional health complications or secondary illnesses. The consequences of nonadherence on an individual's health vary based on the type of illness and the treatment regimen. For example, types of health conditions that require strict adherence toward their treatment regimen and medication include kidney transplantation, end‐stage renal disease, and HIV. The primary cause of kidney transplant rejection for patients is nonadherence toward their immunosuppressant medication (Cukor, Rosenthal, Jindal, Brown, & Kimmel, 2009). Individuals who are nonadherent toward their medication are at an increased risk of rejecting their organ or experiencing kidney failure. Furthermore, for individuals with end‐stage renal disease, adherence to hemodialysis regimens is crucial in order to decrease the individual's risk of earlier mortality or further complications. Individuals diagnosed with HIV face an increased rate of drug resistance to their antiretroviral medication if they are not strictly adherent toward their medication regimen as well. As a result, nonadherence causes an increased risk of mortality and future adverse effects such as faster progression of the virus.
Health conditions that are not solely dependent on medication have been shown to have suboptimal adherence rates. For example, treatment regimens for individuals with diabetes or primary hypertension usually include a complex treatment regimen that includes medication, as well as diet and lifestyle modifications in order to obtain optimal health. Nonadherence to treatment regimens for these health conditions can have an adverse effect on an individual's health over time. Individuals diagnosed with diabetes and are nonadherent can experience adverse complications such as ketoacidosis (diabetic coma), stroke, kidney disease, blindness, damage to the nerves, the development of heart disease, and an increased risk of early mortality. Furthermore, individuals diagnosed with primary hypertension have a treatment plan that usually consists of antihypertensive medication as well as lifestyle change. Nonadherence to antihypertensive medication and behavior change can lead to the development of heart disease, kidney damage, congestive heart failure, and stroke. Therefore, adherence to the agreed‐upon treatment plan is critical to decrease an individual's risk of developing secondary illnesses or adverse complications and to increase the likelihood of optimal health outcomes.
Another consequence of nonadherence is erosion of the physician–patient relationship. Ideally, a patient and physician work together in a collaborative manner using open communication to reach the common goal of good health outcomes for the patient. If a patient does not admit to struggles with adherence, it may be difficult for the physician to trust the patient, and the quality of their relationship can be negatively affected.
There are multiple methods of measuring adherence to treatment, but unfortunately no “gold standard” measurement method exists. Numerous measurement approaches can be used based on the setting and context of the measurement (e.g., clinical settings versus research contexts). Measurement approaches are typically grouped into two categories: direct and indirect methods. Direct methods include direct observation of patients taking their medication and measurement of levels of the medication or metabolite in blood or urine. Direct approaches can be very accurate but may also be more invasive, expensive, and time consuming. Indirect measures include patient self‐reports either via interview or questionnaire, family member reports, pill counts, pharmacy refill records, or electronic monitors (e.g., measurement via special pill bottle caps such as MEMScap™ that record the time and date each time a pill bottle is opened). Each of these measures has both benefits and drawbacks. Pharmacy refill records, for example, can be inaccurate because they do not directly show ingestion of medication or behavior such as incorrect timing of doses. Electronic monitors not only can be very accurate but also are a more expensive way to measure adherence and also do not indicate ingestion of medication. Although self‐report measures can be subject to biases in memory or the desire to present oneself in the best possible light, they do tend to be the simplest, most common, and least expensive approach to adherence measurement. In general, a multimethod approach to measuring adherence is recommended.
Researchers have attempted to understand the factors that influence patient nonadherence and the factors that may promote adherence to treatment. Predictors of nonadherence have been grouped into several categories: patient‐related factors, regimen‐related factors, provider–patient interaction level factors, and healthcare system‐related factors (Osterberg & Blaschke, 2005).
Patient‐related factors that predict nonadherence include such elements as mental health, beliefs and attitudes, understanding, motivation, and social support. Patients with poor mental health (particularly depression) tend to be less adherent. Meta‐analytic work reveals a strong relationship between nonadherence and depression across 31 studies of patients with chronic diseases (Grenard et al., 2011). This association may be due to a pessimistic attitude, forgetfulness, or lack of motivation that often accompanies depression. Furthermore, patients who do not believe in the benefit of their regimen or have negative attitudes toward it may be less adherent. Such patients make a conscious choice not to follow their treatment regimen, as they are not convinced that it will help them or alleviate their symptoms. In addition, patients who do not understand their regimen or how to follow it correctly may be unintentionally nonadherent. When patients first receive instructions on how to take medications, they may not understand the instructions due to poor health literacy (i.e., an inability or struggle to understand and process health‐related information). Also, patients who are lacking in social support, particularly that who comes from a loving family, may also be less adherent (DiMatteo, 2004b). A patient's support network may play many roles in promoting adherence, including giving reminders to the patient, encouraging the patient in their health‐related goals, and providing tangible support such as driving the patient to medical appointments.
There are several regimen‐related factors that may be associated with nonadherence. These include side effects, frequency of dosing, and complexity of the regimen. A review of 61 studies reported that in diseases such as diabetes and HIV, greater dose frequency and more complex regimens (e.g., more medications, special requirements associated with medication taking) are associated with poorer adherence (Ingersoll & Cohen, 2008).
Physician–patient communication is also associated with patient adherence. A meta‐analysis of 106 studies (Zolnierek & DiMatteo, 2009) reported that patients of physicians who communicated effectively had 19% higher adherence. Mutual trust, open communication, sharing in the process of making medical decisions, and partnership are all interpersonal factors in the medical provider–patient relationship that are central to achievement of patient adherence.
Healthcare system factors may also play a role in nonadherence. Numerous studies have indicated that the cost of medications may predict nonadherence, as patients delay refills or take their medication less frequently due to cost issues (Briesacher, Gurwitz, & Soumerai, 2007).
The information–motivation–strategy model has been proposed to explain three basic factors that are central to achievement of adherence (DiMatteo et al., 2012). First, patients do not understand their regimen and how to follow it. They lack the information and understanding needed to adhere. Communication with their physician may have been ineffective, or they may have difficulty understanding the regimen due to poor health literacy or forgetting the instructions they were given. Second, patients may not be motivated and committed to adherence to their treatment regimen. This lack of motivation or commitment could be due to their beliefs about the treatment regimen or their negative attitudes about it or to a lack of support that encourages the patient's adherence. Third, patients may lack the resources and strategies to support adherence. These strategies could include tools to help them remember to take their medication or a plan for getting to the pharmacy for refills. Understanding the predictors of adherence is helpful in designing interventions to improve adherence.
As discussed, adherence is influenced by multiple factors, and researchers have proposed a variety of interventions in an effort to reduce rates of nonadherence. Interventions have been proposed on multiple levels, including patient, provider, and system‐related levels. For example, a policy‐level intervention might involve reducing out‐of‐pocket costs of medications. Unfortunately, fewer than half of published interventions have been found to improve adherence (Haynes, Ackloo, Sahota, McDonald, & Yao, 2008; van Dulmen et al., 2007). Evidence suggests that multifaceted interventions that address multiple barriers to adherence may be most effective. Strategies that have been found to be effective in multicomponent interventions include more intensive communication with and counseling of patients, providing reminders, and providing closer follow‐up (Haynes et al., 2008). A recent review of 182 randomized clinical trials of interventions to improve medication adherence reported that the most successful interventions were complex and personalized and involved several approaches to improving adherence (Nieuwlaat et al., 2014). Examples of these approaches included increased support from family members or personalized care, education, and communication from healthcare providers such as pharmacists.
Educational interventions with monitoring, support, and follow‐up were most strongly associated with improvements in adherence in a systematic review (Viswanathan et al., 2012). These authors compared interventions in various categories of chronic disease and stratified by patient, provider, and system‐level interventions. Specific examples of successful interventions included asthma self‐management and case management interventions for depression (Viswanathan et al., 2012). Other techniques that have been successful include reducing daily dosing frequency and providing reminders in the form of alarms or alerts, which can be helpful with the unintentional aspect of nonadherence.
In promoting patient adherence, it will continue to be important to be aware of and address barriers at the patient, provider, and system levels. In addition, future research should continue to study the most successful components of interventions and improve these interventions to enhance adherence and health outcomes.
Kelly B. Haskard‐Zolnierek is an associate professor of psychology at Texas State University. Her research involves two main areas: patients' adherence to medical recommendations and medical visit communication in the provider–patient relationship. Her current research involves evaluating mobile health interventions to improve patient adherence. Dr. Haskard‐Zolnierek has coauthored a book on patient adherence, published in 2010 by Oxford University Press, and a 2009 meta‐analysis of the relationship between physician communication skills and patient adherence.
Briana Cobos completed her master of arts degree at Texas State University in psychological research. Her general research area is in health psychology. Ms. Cobos' research interests include predictors of nonadherence in individuals diagnosed with both a mental health condition and a chronic illness. She has coauthored various papers with a focus in health psychology and mental health conditions.