adherence (medicine) adherence (medicine) 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. access to care plays a role in patient adherence, whereby greater wait times to access care contributing to greater absenteeism. the cost of prescription medication also plays a major role. this article is about following medical advice. for the physiological term, see compliance (physiology). for other uses, see compliance. part of a series onmedical sociology concepts medicalization doctor-patient relationship shared decision making sick role labelling theory adherence social model of disability sociologists talcott parsons eliot freidson peter conrad ivan illich related topics sociology social medicine public health category compliance can be confused with concordance, which is the process by which a patient and clinician make decisions together about treatment. 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. major barriers to compliance are thought to include the complexity of modern medication regimens, poor "health literacy" and not understanding treatment benefits, the 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. 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. it is still unclear how adherence can consistently be improved in order to promote clinically important effects. terminology 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. 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. 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. it has been noted that compliance may only refer to passively following orders. the term adherence is often used to imply a collaborative approach to decision-making and treatment between a patient and clinician. 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. informed intentional non-adherence is when the patient, after understanding the risks and benefits, chooses not to take the treatment. as of 2005, the preferred terminology remained a matter of debate. 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. despite the ongoing debate, adherence has been the preferred term for the world health organization, the american pharmacists association, and the u.s. national institutes of health adherence research network. 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. adherence factors an estimated half of those for whom treatment regimens are prescribed do not follow them as directed. side effects negative side effects of a medicine can influence adherence.: 280 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. there is robust evidence that education and physical health are correlated. poor educational attainment is a key factor in the cycle of health inequalities. educational qualifications help to determine an individual's position in the labour market, their level of income and therefore their access to resources. literacy 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. 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. low levels of literacy and numeracy were found to be associated with socio-economic deprivation. 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. a 2002 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. 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. 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. in 2009, this contributed to an estimated cost of $290 billion annually. in 2012, increase in patient medication cost share was found to be associated with low adherence to medication. 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. 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. 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". 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. age 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. 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. 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 the medication that they were prescribed 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. comprehension, polypharmacy, living arrangement, multiple doctors, and use of compliance aids was correlated with adherence. in children with asthma self-management compliance is critical and co-morbidities have been noted to affect outcomes; in 2013 it has been suggested that electronic monitoring may help adherence. social factors of treatment adherence have been studied in children and adolescents with disorders: young people who felt supported by their family and doctor, and had good motivation, were more likely to comply. young adults may stop taking prescribed medication in order to fit in with their friends, or because they lack insight of their illness. 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. non-adherence is often encountered among children and young adults; young males are relatively poor at adherence. ethnicity people of different ethnic backgrounds have unique adherence issues through literacy, physiology, culture or poverty. 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. 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. 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. recent studies have shown that black patients and those with non-private insurance are more likely to be labeled as non-adherent. the increased risk is observed even in patients with a controlled a1c, and after controlling for other socioeconomic factors. 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. reasons people do not fill prescriptions include the cost of the medication, 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. other factors are doubting the need for medication, or preference for self-care measures other than medication. convenience, side effects and lack of demonstrated benefit are also factors. 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'. two forms of mpr can be calculated, fixed and variable. calculating either is relatively straightforward, for variable mpr (vmpr) it is calculated as the