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Adherence (medicine)

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In medicine, patient compliance (also adherence, capacitance) describes the degree to which a patient correctly follows medical advice. Most commonly, it refers to medication or drug compliance, but it can also apply to other situations such as medical device use, self care, self-directed exercises, or therapy sessions. Both patient and health-care provider affect compliance, and a positive physician-patient relationship is the most important factor in improving compliance,[1] The cost of prescription medication also plays a major role.[2]

Compliance can be confused with concordance, which is the process by which a patient and clinician make decisions together about treatment.[3]

Worldwide, non-compliance is a major obstacle to the effective delivery of health care. 2003 estimates from the World Health Organization indicated that only about 50% of patients with chronic diseases living in developed countries follow treatment recommendations with particularly low rates of adherence to therapies for asthma, diabetes, and hypertension.[1] Major barriers to compliance are thought to include the complexity of modern medication regimens, poor "health literacy" and not understanding treatment benefits, occurrence of undiscussed side effects, poor treatment satisfaction, cost of prescription medicine, and poor communication or lack of trust between a patient and his or her health-care provider.[4][5][6][7] Efforts to improve compliance have been aimed at simplifying medication packaging, providing effective medication reminders, improving patient education, and limiting the number of medications prescribed simultaneously. Studies show a great variation in terms of characteristics and effects of interventions to improve medicine adherence.[8] It is still unclear how adherence can consistently be improved in order to promote clinically important effects.[8]


In medicine, compliance (synonymous with adherence, capacitance) describes the degree to which a patient correctly follows medical advice. Most commonly, it refers to medication or drug compliance, but it can also apply to medical device use, self care, self-directed exercises, or therapy sessions. Both patient and health-care provider affect compliance, and a positive physician-patient relationship is the most important factor in improving compliance,[1]

As of 2003, US health care professionals more commonly used the term "adherence" to a regimen rather than "compliance", because it has been thought to reflect better the diverse reasons for patients not following treatment directions in part or in full.[5][9] Additionally, the term adherence includes the ability of the patient to take medications as prescribed by their physician with regards to the correct drug, dose, route, timing, and frequency.[10] It has been noted that compliance may only refer to passively following orders.[11]

The term concordance has been used in the United Kingdom to involve a patient in the treatment process to improve compliance, and refers to a 2003 NHS initiative. In this context, the patient is informed about their condition and treatment options,involved in the decision as to which course of action to take, and partially responsible for monitoring and reporting back to the team.[12]

As of 2005, the preferred terminology remained a matter of debate.[13] As of 2007, concordance has been used to refer specifically to patient adherence to a treatment regimen which the physician sets up collaboratively with the patient, to differentiate it from adherence to a physician-only prescribed treatment regimen.[14][15][16] Despite the ongoing debate, adherence has been the preferred term for the World Health Organization,[1] The American Pharmacists Association,[4] and the U.S. National Institutes of Health Adherence Research Network.[17] The Medical Subject Headings of the United States National Library of Medicine defines various terms with the words adherence and compliance. Patient Compliance and Medication Adherence are distinguished under the MeSH tree of Treatment Adherence and Compliance.

Compliance factors

An estimated half of those for whom treatment regimens are prescribed do not follow them as directed.[1] Until recently,[when?] this was termed "non-compliance", which some regarded as meaning that someone did not follow the treatment directions due to irrational behavior or willful ignoring of instructions.[citation needed]

Health literacy

Cost and poor understanding of the directions for the treatment, referred to as 'health literacy' have been known to be major barriers to treatment adherence.[18][5][19] There is robust evidence that education and physical health are correlated. Poor educational attainment is a key factor in the cycle of health inequalities.[20][21][22]

Educational qualifications help to determine an individual's position in the labour market, their level of income and therefore their access to resources.[citation needed]


In 1999 one fifth of UK adults, nearly seven million people, had problems with basic skills, especially functional literacy and functional numeracy, described as: "The ability to read, write and speak in English, and to use mathematics at a level necessary to function at work and in society in general." This made it impossible for them to effectively take medication, read labels, follow drug regimes, and find out more.[23]

In 2003, 20% of adults in the UK had a long-standing illness or disability and a national study for the UK Department of Health, found more than one-third of people with poor or very poor health had literary skills of Entry Level 3 or below.[24]

Low levels of literacy and numeracy were found to be associated with socio-economic deprivation.[24] Adults in more deprived areas, such as the North East of England, performed at a lower level than those in less deprived areas such as the South East. Local authority tenants and those in poor health were particularly likely to lack basic skills.[24]

A 2000 analysis of over 100 UK local education authority areas found educational attainment at 15–16 years of age to be strongly associated with coronary heart disease and subsequent infant mortality.[25]

A study of the relationship of literacy to asthma knowledge revealed that 31% of asthma patients with a reading level of a ten-year-old knew they needed to see the doctors, even when they were not having an asthma attack, compared to 90% with a high school graduate reading level.[26]

Treatment cost

In 2013 the US National Community Pharmacists Association sampled for one month 1,020 Americans above age 40 for with an ongoing prescription to take medication for a chronic condition and gave a grade C+ on adherence.[27][better source needed] In 2009, this contributed to an estimated cost of $290 billion annually.[28] In 2012, increase in patient medication cost share was found to be associated with low adherence to medication.[29]

The United States is among the countries with the highest prices of prescription drugs mainly attributed to the government's lack of negotiating lower prices with monopolies in the pharmaceutical industry especially with brand name drugs.[30] In order to manage medication costs, many US patients on long term therapies fail to fill their prescription, skip or reduce doses. According to a Kaiser Family Foundation survey in 2015, about three quarters (73%) of the public think drug prices are unreasonable and blame pharmaceutical companies for setting prices so high.[31] In the same report, half of the public reported that they are taking prescription drugs and a "quarter (25%) of those currently taking prescription medicine report they or a family member have not filled a prescription in the past 12 months due to cost, and 18 percent report cutting pills in half or skipping doses".[31] In a 2009 comparison to Canada, only 8% of adults reported to have skipped their doses or not filling their prescriptions due to the cost of their prescribed medications.[32]


Both young and elderly status have been associated with non-adherence.

The elderly often have multiple health conditions, and around half of all NHS medicines are prescribed for people over retirement age, despite representing only about 20% of the UK population.[33][34] The recent National Service Framework on the care of older people highlighted the importance of taking and effectively managing medicines in this population. However, elderly individuals may face challenges, including multiple medications with frequent dosing, and potentially decreased dexterity or cognitive functioning. Patient knowledge is a concern that has been observed.

In 1999 Cline et al. identified several gaps in knowledge about medication in elderly patients discharged from hospital.[35] Despite receiving written and verbal information, 27% of older people discharged after heart failure were classed as non-adherent within 30 days. Half the patients surveyed could not recall the dose of their medication and nearly two-thirds did not know what time of day to take them. A 2001 study by Barat et al. evaluated the medical knowledge and factors of adherence in a population of 75-year-olds living at home. They found that 40% of elderly patients do not know the purpose of their regimen and only 20% knew the consequences of non-adherence.[36] Comprehension, polypharmacy, living arrangement, multiple doctors, and use of compliance aids was correlated with adherence. According to a conservative estimate 10% of all hospital admissions[where?] are through patients not managing their medication.[citation needed]

In children with asthma self-management compliance is critical and co-morbidites have been noted to affect outcomes; in 2013 it has been suggested that electronic monitoring may help adherence.[37]

Social factors of treatment adherence have been studied in children and adolescent psychiatric disorders:

  • Young people who felt supported by their family and doctor, and had good motivation, were more likely to comply.[38]
  • Young adults may stop taking their medication in order to fit in with their friends, or because they lack insight of their illness.[38]
  • Those who did not feel their condition to be a threat to their social well-being were eight times more likely to comply than those who perceived it as such a threat.[39][40]
  • Non-adherence is often encountered among children and young adults; young males are relatively poor at adherence.[41][42]


People of different ethnic backgrounds have unique adherence issues through literacy, physiology, culture or poverty.[citation needed] There are few published studies on adherence in medicine taking in ethnic minority communities. Ethnicity and culture influence some health-determining behaviour, such as participation in screening programmes and attendance at follow-up appointments.[43][44]

Prieto et al emphasised the influence of ethnic and cultural factors on adherence. They pointed out that groups differ in their attitudes, values and beliefs about health and illness. This view could affect adherence, particularly with preventive treatments and medication for asymptomatic conditions. Additionally, some cultures fatalistically attribute their good or poor health to their god(s), and attach less importance to self-care than others.[45] also

Measures of adherence may need to be modified for different ethnic or cultural groups. In some cases, it may be advisable to assess patients from a cultural perspective before making decisions about their individual treatment.[citation needed]

Prescription fill rates

Not all patients will fill the prescription at a pharmacy. In a 2010 U.S. study, 20–30% of prescriptions were never filled at the pharmacy.[46][47] Reasons people do not fill prescriptions include the cost of the medication,[2][4] A US nationwide survey of 1,010 adults in 2001 found that 22% chose not to fill prescriptions because of the price, which is similar to the 20–30% overall rate of unfilled prescriptions.[2] Other factors are doubting the need for medication, or preference for self-care measures other than medication.[48][49] Convenience, side effects and lack of demonstrated benefit are also factors.[citation needed]

Medication Possession Ratio

Prescription medical claims records can be used to estimate medication adherence based on fill rate. Patients can be routinely defined as being 'Adherent Patients' if the amount of medication furnished is at least 80% based on days' supply of medication divided by the number of days patient should be consuming the medication. This percentage is called the medication possession ratio (MPR). 2013 work has suggested that a medication possession ratio of 90% or above may be a better threshold for deeming consumption as 'Adherent'.[50]

Two forms of MPR can be calculated, fixed and variable.[51] Calculating either is relatively straightforward, for Variable MPR (VMPR) it is calculated as the number of days' supply divided by the number of elapsed days including the last prescription.

<math> VMPR = \dfrac{\text{All days' supply}}{\text{Elapsed days (inclusive of last prescription)}} </math>

For the Fixed MPR (FMPR) the calculation is similar but the denominator is the number of days in a year whilst the numerator is constrained to be the number of days' supply within the year that the patient has been prescribed.

<math> FMPR = \dfrac{\text{All days' supply} \le 365}{365} </math>

For medication in tablet form it is relatively straightforward to calculate the number of days' supply based on a prescription. Some medications are less straightforward though because a prescription of a given number of doses may have a variable number of days' supply because the number of doses to be taken per day varies, for example with preventative corticosteroid inhalers prescribed for asthma where the number of inhalations to be taken daily may vary between individuals based on the severity of the disease.[citation needed]

Course completion

Once started, patients seldom follow treatment regimens as directed, and seldom complete the course of treatment.[4][5] In respect of hypertension, 50% of patients completely drop out of care within a year of diagnosis.[52] Persistence with first-line single antihypertensive drugs is extremely low during the first year of treatment.[53] As far as lipid-lowering treatment is concerned, only one third of patients are compliant with at least 90% of their treatment.[54] Intensification of patient care interventions (e.g. electronic reminders, pharmacist-led interventions, healthcare professional education of patients) improves patient adherence rates to lipid-lowering medicines, as well as total cholesterol and LDL-cholesterol levels.[55]

The World Health Organization (WHO) estimated in 2003 that only 50% of people complete long-term therapy for chronic illnesses as they were prescribed, which puts patient health at risk.[56] For example, in 2002 statin compliance dropped to between 25–40% after two years of treatment, with patients taking statins for what they perceive to be preventative reasons being unusually poor compliers.[57]

A wide variety of packaging approaches have been proposed to help patients complete prescribed treatments. These approaches include formats that increase the ease of remembering the dosage regimen as well as different labels for increasing patient understanding of directions.[58][59] For example, medications are sometimes packed with reminder systems for the day and/or time of the week to take the medicine.[59] Some evidence shows that reminder packaging may improve clinical outcomes such as blood pressure.[59]

A not-for-profit organisation called the Healthcare Compliance Packaging Council of Europe] (HCPC-Europe) was set up[when?] between the pharmaceutical industry, the packaging industry with representatives of European patients organisations. The mission of HCPC-Europe is to assist and to educate the healthcare sector in the improvement of patient compliance through the use of packaging solutions. A variety of packaging solutions have been developed by this collaboration.[60]

World Health Organization Barriers to Adherence

The World Health Organization (WHO) groups barriers to medication adherence into five categories; health care team and system-related factors, social and economic factors, condition-related factors, therapy-related factors, and patient-related factors. Common barriers include:[61]

Barrier Category
Poor Patient-provider Relationship Health Care Team and System
Inadequate Access to Health Services Health Care Team and System
High Medication Cost Social and Economic
Cultural Beliefs Social and Economic
Level of Symptom Severity Condition
Availability of Effective Treatments Condition
Immediacy of Beneficial Effects Therapy
Side Effects Therapy
Stigma Surrounding Disease Patient
Inadequate Knowledge of Treatment Patient

Improving compliance rates

Role of health care providers

Health care providers play a great role in improving adherence issues. Providers can improve patient interactions through motivational interviewing and active listening.[62] Health care providers should work with patients to devise a plan that is meaningful for the patient's needs. A relationship that offers trust, cooperation, and mutual responsibility can greatly improve the connection between provider and patient for a positive impact.[11]


In 2012 it was predicted that as telemedicine technology improves, physicians will have better capabilities to remotely monitor patients in real-time and to communicate recommendations and medication adjustments using personal mobile devices, such as smartphones, rather than waiting until the next office visit.[63]

Medication Event Monitoring Systems, as in the form of smart medicine bottle tops, smart pharmacy vials or smart blister packages as used in clinical trials and other applications where exact compliance data are required, work without any patient input, and record the time and date the bottle or vial was accessed, or the medication removed from a blister package. The data can be read via proprietary readers, or NFC enabled devices, such as smartphones or tablets. A 2009 study stated that such devices can help improve adherence.[64]

Health and disease management

A WHO study estimates that only 50% of patients suffering from chronic diseases in developed countries follow treatment recommendations.[1] The

Asthma non-compliance (28–70% worldwide) increases the risk of severe asthma attacks requiring preventable ER visits and hospitalisations; compliance issues with asthma can be caused by a variety of reasons including: difficult inhaler use, side effects of medications, and cost of the treatment.[65]


200,000 new cases of cancer are diagnosed each year in the UK. One in three adults in the UK will develop cancer that can be life-threatening, and 120,000 people will be killed by their cancer each year. This accounts for 25% of all deaths in the UK. However while 90% of cancer pain can be effectively treated, only 40% of patients adhere to their medicines due to poor understanding.[citation needed]

The reasons for non-adherence have been given by patients as follows:

Partridge et al (2002) identified evidence to show that adherence rates in cancer treatment are variable, and sometimes surprisingly poor. The following table is a summary of their findings:[66]

Type of Cancer Measure of non-Adherence Definition of non-Adherence Rate of Non-Adherence
Haematological malignancies Serum levels of drug metabolites Serum levels below expected threshold 83%
Breast cancer Self-report Taking less than 90% of prescribed medicine 47%
Leukemia or non Hodgkin's lymphoma Level of drug metabolite in urine Level lower than expected 33%
Leukemia, Hodgkin's disease, non Hodgkin's Self-report and parent report More than one missed dose per month 35%
Lymphoma, other malignancies Serum bioassay Not described
Hodgkin's disease, acute lymphocytic leukemia (ALL) Biological markers Level lower than expected 50%
ALL Level of drug metabolite in urine Level lower than expected 42%
ALL Level of drug metabolites in blood Level lower than expected 10%
ALL Level of drug metabolites in blood Level lower than expected 2%
  • Medication event monitoring system - a medication dispenser containing a microchip that records when the container is opened and from Partridge et al (2002)

In 1998, trials evaluating Tamoxifen as a preventative agent have shown dropout rates of around one-third:

  • 36% in the Royal Marsden Tamoxifen Chemoprevention Study of 1998[67]
  • 29% in the National Surgical Adjuvant Breast and Bowel Project of 1998[68]

In March 1999, the "Adherence in the International Breast Cancer Intervention Study" evaluating the effect of a daily dose of Tamoxifen for five years in at-risk women aged 35–70 years was[69]

  • 90% after one year
  • 83% after two years
  • 74% after four years


Patients with diabetes are at high risk of developing coronary heart disease and usually have related conditions that make their treatment regimens even more complex, such as hypertension, obesity and depression[70] which are also characterised by poor rates of adherence.[71]

  • Diabetes non-compliance is 98% in US[citation needed] and the principal cause of complications related to diabetes including nerve damage and kidney failure.[citation needed]
  • Among patients with Type 2 Diabetes, adherence was found in less than one third of those prescribed sulphonylureas and/or metformin. Patients taking both drugs achieve only 13% adherence.[72]


  • Hypertension non-compliance (93% in US, 70% in UK)[citation needed] is the main cause of uncontrolled hypertension-associated heart attack and stroke.
  • In 1975, only about 50% took at least 80% of their prescribed anti-hypertensive medications.[73]

As a result of poor compliance,[citation needed] 75% of patients with a diagnosis of hypertension do not achieve optimum blood-pressure control.[citation needed]

Mental illness

A 2003 review found that 41–59% of mentally ill patients took their medication infrequently or not at all.[74]

A 2006 review investigated the effects of compliance therapy for schizophrenia: and found no clear evidence to suggest that compliance therapy was beneficial for people with schizophrenia and related syndromes.[75]

See also


  1. 1.0 1.1 1.2 1.3 1.4 1.5
  2. 2.0 2.1 2.2
  3. 4.0 4.1 4.2 4.3
  4. 5.0 5.1 5.2 5.3
  5. 8.0 8.1
  6. Viswanathan M, Golin CE, Jones CD, Ashok M, Blalock S, Wines RCM, Coker-Schwimmer EJL, Grodensky CA, Rosen DL, Yuen A, Sista P, Lohr KN. Medication Adherence Interventions: Comparative Effectiveness. Closing the Quality Gap: Revisiting the State of the Science. Archived 2017-01-06 at the Wayback Machine Evidence Report No. 208. Prepared by RTI International–University of North Carolina Evidence-based Practice Center under Contract No. 290-2007-10056-I. AHRQ Publication No. 12-E010-EF. Rockville, MD: Agency for Healthcare Research and Quality. September 2012.
  7. 11.0 11.1
  8. Donald Acheson (1998). Independent inquiry into inequalities in health (Report).
  9. Tackling health inequalities (Report). HM Government. 2002.
  10. Moser Report Summary, 14 pages (1999)retrieved 28. 12. 2017
  11. 24.0 24.1 24.2
  12. New Report Card on Medication Use Gives Americans a C+ Pharmacy Times. JUNE 25, 2013
  13. Thinking Outside the Pillbox: A System-wide Approach to Improving Patient Adherence for Chronic Disease." NEHI. 2009
  14. 31.0 31.1 Kaiser Family Foundation: Poll Finds Nearly Three Quarters of Americans Say Prescription Drug Costs Are Unreasonable, and Most Blame Drug Makers Rather Than Insurers for the Problem
  15. UK Department of Health (2001): National Service Framework for Older People, London.
  16. UK Office of Health Economics (2000): Compendium of Health Statistics, 12th Edition, London.
  17. 38.0 38.1
  18. 59.0 59.1 59.2
  19. Healthcare Compliance Packaging Council of Europe
  20. Stefanacci, Richard G., DO, MGH, MBA, AGSF, CMD, and Scott Guerin, PhD. "Why Medication Adherence Matters To Patients, Payers, Providers." Managed Care Jan. 2013. Accessed Nov 2, 2014
  21. Marisa Torrieri, "Patient compliance: technology tools for physicians" Physicians Practice, September 2012.

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