Disclaimer: The findings and conclusions in this document are those of the author and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
“Drugs don’t work in patients who don’t take them.”
Medication adherence is a major and growing public health concern. However, adherence to antihypertension medication is crucial to not only hypertension control, but in saving lives.
“High adherence to antihypertensive medication is associated with higher odds of blood pressure control, but nonadherence to cardioprotective medications increases a patient’s risk of death from 50% to 80%.” Although studies report wide ranges for antihypertensive medication adherence attributed to varying methodologies of estimated nonadherence, one-third to one-half of first prescriptions are never filled, and only 15% to 20% of prescriptions are refilled and continued as prescribed ( Fig. 49.1 ). It is estimated that between one-third and two-thirds of medication-related hospital admissions are as a result of poor adherence. Based on NHANES (National Health and Nutrition Examination Survey) data, 29.3% of adults in the United States have hypertension (2013-2014), 75.6% were on medication (2011-2012), and only 54.0% were controlled (2013-2014). Thus 3 in 10 adults taking medication for hypertension remain uncontrolled. Poor adherence to medication is an important reason for not achieving hypertension control.
There are many definitions of medication adherence but most of them refer to two concepts: adherence or compliance, which refers to taking medication as prescribed by their health care provider with respect to timing, dosage, and frequency, and persistence, which is continuing to take the medication for the duration that the medication was prescribed ( Fig. 49.2 ). Additionally, some people refer to never getting a first prescription filled as primary nonadherence and secondary nonadherence as not taking the medication as prescribed. The World Health Organization defines adherence as the extent to which a person’s behavior, in this case taking medication, corresponds with the agreed upon recommendations from a health care provider. Medication adherence involves a complex cluster of behaviors and is affected by multiple factors, including patient-related factors, provider factors, health care system factors, condition-related factors, therapy-related factors, and social/economic factors. Medication adherence has been extensively studied for antihypertensive medications because they are so commonly prescribed and adherence is key to control of hypertension. In a 2004 study, it was estimated that 8.3 million office visits per year for hypertension likely ended with nonadherence to prescribed medication. According to a survey by the National Community Pharmacists Association, of adults aged 40 years and older, the most commonly prescribed medication for a chronic condition was antihypertensive medication, with 57% of survey respondents reporting taking medication for hypertension.
Effective control of hypertension can significantly reduce the rates of stroke and other cardiovascular diseases, and death. Data from clinical trials, which tend to have high rates of medication adherence, have shown that antihypertensive medication can reduce the risk of stroke by 18% to 40%, the risk of myocardial infarction by 15%, and all-cause mortality up to 60% over an average follow-up of 2 to 3 years. Several studies have shown the direct relationship between improved antihypertensive medication adherence and improved rates of blood pressure control. Studies looking at short-term levels of medication adherence with disease-related health care costs and hospitalization risk for hypertension, found that in general overall health care costs increased with decreasing quintiles of medication adherence despite increased medication costs with better adherence, and those with lower medication adherence had increasing risk for hospitalization ( Fig. 49.3 ).
Predictors of Nonadherence
Medication adherence involves a complex set of behaviors, conditions, and policies that must operate in a coordinated manner and must be individualized for each patient ( Box 49.1 ). More than 100 factors have been identified to be associated with medication adherence. Only half of Americans treated for hypertension are adherent to their long-term therapy. In a recent survey, when asked about nonadherence behaviors, three out of four adult respondents were engaging in at least one of seven nonadherence behaviors (57% had missed doses, 20% did not fill the prescription, and 14% stopped taking the medication). Items identified as strong predictors of medication adherence were connectedness with a pharmacist and always seeing the same doctor, affordability was the second-strongest predictor of adherence, and other predictors were feeling informed about one’s health and knowing the importance of taking medication as prescribed. Fischer et al. found that between 26.4% and 28.4% of antihypertensive medication e-prescriptions were never filled the first time the medication was prescribed; yet e-prescriptions for antihypertensives for which the patient had already been taking the medication were more likely to be filled with only 9.8% of antihypertensive e-prescription not being filled. They also found that electronic prescriptions sent to a pharmacy were more likely to be filled than printed prescriptions given to the patient, and that e-prescriptions sent directly to a mail-order service were most likely to be filled, because it required no action on the part of the patient.
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Low literacy/limited English language proficiency
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Homelessness
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Depression
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Psychiatric disease
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Substance abuse
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Lower cognitive function or cognitive impairment
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Forgetfulness
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Anger, psychological stress, anxiety
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Lack of insight into illness
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Lack of belief in benefit of treatment
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Belief medications are not important or are harmful
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Complexity of medication regimen
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Tired of taking medications
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Inconvenience of medication regimen
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Side effects or fear of medication side effects
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Cost of medication, copayment, or both
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Barriers to access to care or medications
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Inadequate follow-up or discharge planning missed appointments
Reasons for Nonadherence
Health care system factors that affect medication adherence include lack of continuity with a care provider or seeing a different care provider each time care is accessed, as can the cost of medication, lack of educational materials about hypertension, and the importance of taking medication as prescribed that are not culturally appropriate or are written at too high of a literacy level ( Fig. 49.4 ). Provider-related factors that affect adherence include provider communication skills, lack of positive reinforcement from the provider regarding medication adherence, long wait times at appointments, weak capacity of the provider to educate the patient on their condition, differences between the health beliefs of the provider and the patient, and a less than optimal provider-patient relationship. Therapy-related factors include complicated medication regimens or regimens that are inconvenient for the patient, and side effects of the medication. Multiple chronic conditions, especially those that cause the patient to be symptomatic or feel ill, can compete for the patient’s attention to medication adherence for a condition such as hypertension, which typically does not have symptoms, conditions such as depression, mental health conditions such as psychosis, and a general lack of symptoms with hypertension can lead to poor adherence. Social and economic-related factors that can hinder medication adherence, including limited English proficiency, medication cost, lack of family support, homelessness, and cultural beliefs about the health care system, illness, or treatment. Lastly, there are patient-related factors that contribute to poor adherence, but it is important to recognize that not all of them are controllable by the patient. Impairments such as visual, hearing, cognitive, mobility, or swallowing problems can have an effect on the patient’s ability to take the medication as prescribed. Other contributing factors that influence adherence include depression, fear of potential side effects, lack of knowledge about the disease, lack of confidence in their ability to take the medication as prescribed, fear of being stigmatized or labeled as ‘having a disease,’ lack of belief or confidence in the health care system, expectations or attitudes about the medication that may or may not be unfounded, motivation, forgetfulness, interference with their lifestyle or work schedules, and substance abuse.
A recent consumer survey asked respondents about their reasons for not taking their blood pressure medication as prescribed. Overall, 30.5% admitted to not taking their medication as directed. The most common reasons for nonadherence were forgetting to take it (23.6%), not thinking they need it (27.1%), and not being able to afford it (35.1%). Similarly, when asked about their rationale for nonadherence 39.2% said they were exercising more, 41.9% said they were trying to lose or had lost weight, 42.4% said they were changing their eating habits, and 53.1% said they were cutting down on salt. Adherence was significantly associated with lower income, Hispanic ethnicity, younger age, and depression.
Strategies and Interventions to Improve Adherence
Strategies to improve medication adherence are based on effective communication, effective interventions, and measuring medication adherence ( Box 49.2 ). A collaborative communication style has been associated with improved medication adherence. Ratanawongsa and colleagues conducted a cross-sectional study within a single health care system of 9377 patients with diabetes on medication adherence to hypoglycemic agents, lipid-lowering medications, and antihypertensive medications. Patients who offered lower ratings of their health care provider were more likely to have poor medication adherence. Specifically, involving patients in decision making increased medication adherence by 4% ( p = 0.04), when the patient thought the provider understood their problem with treatment, adherence increased by 5% ( p = 0.02), and patients who felt that the provider displayed confidence and gained the patient’s trust improved adherence by 6% ( p = 0.03).
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Connectedness with a pharmacist and always seeing the same doctor
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Affordability
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Feeling informed about one’s health and knowing the importance of taking medication as prescribed
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Providers who elicit trust and confidence
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Involving the patient in decision making
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Provider understands the patient’s problem(s)
Differing attitudes and beliefs towards health affect engagement in positive health behaviors. Understanding a patient’s cultural beliefs about a condition such as hypertension is important in gaining patient engagement in hypertension self-management including medication adherence. Motivational interviewing has been used to promote behavior change in various settings such as reducing health-risk behaviors, smoking cessation, and improving medication adherence. It consists of five core principles:
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Develop discrepancy: assist the patient in identifying the discrepancy between their current behavior and the desired goal of medication adherence.
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Express empathy: establish and maintain rapport with the patient with engaged listening without judging.
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Avoid argumentation and the ‘righting reflex’: instead focus on helping the patient with self-recognition of the problem rather than just trying to ‘fix it.’
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Roll with resistance: involve the patient in problem solving to improve adherence.
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Support self-efficacy: support and assist the patient in setting realistic strategies and goals to improve adherence.
Ogedegbe conducted a trial of motivational interviewing compared with usual care among 190 antihypertensive African Americans. The group that received motivational interviewing had significantly improved rates of adherence compared with usual care and improved reduction in systolic blood pressure.
Effective Interventions to Reduce Medication Nonadherence Should be “Simple”
Using the SIMPLE mnemonic can improve patient adherence ( Fig. 49.5 ).
Simplifying the medication regimen can go a long way toward improving medication adherence, such as using a combination antihypertensive or by using a once-a-day regimen, taking into account other medications that the patient is on, and being aware of the patient’s activities of daily living that can interfere with medication adherence are extremely important. Inquire as to whether the patient would like to manage his or her medications with daily reminders (alarms, electronic reminders, etc.), dose-dispensing units of medication, or pill boxes, because these may all improve adherence. Consider changing the situation to meet the patient’s needs rather than changing the patient to fit the regimen. Engage the patient in the discussion of the regimen.
Imparting knowledge about hypertension, that it typically has no symptoms but can still be causing harm, and providing culturally appropriate information that is easy to understand, can improve medication adherence. Again, engaging in provider-patient shared decision making can improve adherence. Keep the care team (physicians, pharmacists, nurses, community health workers) informed of the plan as well as engaging the patient’s family or caregiver. Using a team-based approach to hypertension management can reinforce patient-provider discussions, directions for taking medication as well as addressing low-health literacy and cultural competency. Using a teach-back method can also improve the patient’s knowledge and understanding of hypertension and the importance of taking their medication. Patients that may be vulnerable to low health literacy include older adults, those with multiple chronic conditions, minority populations, and those with limited English proficiency, the medically underserved. Low health literacy can make it especially challenging to understand medication directions. Familiarize your entire health care team with health literacy resources.
Modifying patient beliefs and human behavior by empowering them to self-manage their hypertension can take time but may be very powerful in ensuring good medication adherence. Understanding patient beliefs about hypertension and medications as well as understanding the patient’s confidence in his or her ability to follow through on medication adherence is important. Ensure that patients understand their particular risk if they don’t take their medication, and ask them about the consequences of not taking their medication. Use motivational interviewing to understand their beliefs and engaging them to modify their beliefs, especially if they have fears about taking medication or would benefit from rewards for adherence.
Provide communication and trust as identified in the study by Ratanawongsa ; providers who put effort into generating trust and confidence results in improved medication adherence. Again, use motivational interviewing to improve your communication skills and be an active listener when communicating with your patient. Provide emotional support to encourage the desired behavior of medication adherence, including using your health care team to provide the right support for each patient. Use plain language that is clear, direct, and thorough, as well as culturally appropriate, and remember to ask for patient input on treatment decisions. Understand if cost is a barrier and provide advice on how to cope with this as well as providing lower-cost generics if appropriate.
Leave the bias. The beliefs a person hold regarding their power to affect situations strongly influences both the power a person actually has to face challenges competently and the choices the person is most likely to make. This is apparent and compelling with regard to health behaviors. Providers should inquire about and understand the patient’s attitudes and beliefs about medication therapy as well as their self-efficacy beliefs about their capacity to accomplish a task, such as taking their medication as directed. Motivational interviewing and a team-based approach to hypertension control can improve patients’ self-efficacy and allows providers to best tailor interventions to improve medication adherence.
Evaluate adherence. There are many ways to evaluate medication adherence and different ways can contribute important information at the individual patient level as well as at the provider’s population level. Self-report is perhaps the simplest but may not be the most accurate for an entire patient population. However, it is important to ask about adherence at each patient visit. The team can review medication containers, or work with the pharmacist to identify late medication refill dates. Some patients may be more likely to respond to a quick survey using any of the validated antihypertensive medication adherence scales.
