El desarrollo de la metáfora de la organización celular

The NHP was developed in the 1970s by a group of researchers in the Department of Community Health at Nottingham University. The instrument was designed to reflect lay people’s perception of health as opposed to the medical professional assessment of patient health. It was created based on a pool of more than 2000 statements collected from in-person interviews that enabled the researchers to identify key concepts. Researchers reduced the number of statements to 38 for the first part and seven

statements for the second part. Statements require a ‘Yes’ or ‘No’ response. The first part assesses perceived or subjective health, and statements fall into six domains: sleep, physical mobility, energy, pain, emotional reactions and social isolation. The first part is scored using weighted values, which results in scores ranging from 0 to 100 for each section. The higher the score on any section, the greater the severity of the perceived problems in that domain (Coons, Rao, Keininger, & Hays, 2000; Hunt, McEwen, & McKenna, 1985). The second part focuses on the domains of the daily life, which are

mostly affected by health: paid employment, jobs around the house, social life, personal relationships, sex life, hobbies and interests, and holidays (Hunt et al., 1985). The developers of the NHP have recommended that the second part should no longer be used (Bowling, 1991; Coons et al., 2000).

2.5 Medication Adherence

According to the World Health Organization, adherence is defined as “the extent to which a person’s behavior (i.e., taking medications, following a diet, or making healthy lifestyle changes) corresponds with agreed upon recommendations from a healthcare provider” (Sabaté, 2003, p.136). However, medication adherence can also be defined as the degree to which patients’ or their caregivers’ medications administration behavior coincides with their physicians’ advice with regard to timing, dosage, and frequency of administration during the prescribed time window (Osterberg & Blaschke, 2005). Adherence to prescribed medications is difficult for patients in general and particularly challenging for elderly. Multiple factors influence the elderly patients’ adherence to their prescribed treatment regimens. Elderly patients’ sociodemographic (age, race, sex, and education), medical (comorbidities, number of medications, and treatment of adverse events), psycho-behavioral (beliefs about medicine, understanding of the medical condition, and satisfaction with treatment), and economic (type of insurance, co- payments and coinsurance) characteristics are potential factors that can influence the elderly patients’ adherence to their prescribed medications (Gellad, Grenard, & Marcum, 2011; MacLaughlin et al., 2005; Sa’ed et al., 2013) (Figure 2-2).

The relationship between each of these factors and medication adherence is far from being simple and clear. For instance, older adults are often assumed to have lower adherence to their prescribed medications compared to younger adults. However, this is not always the case. Some studies have shown that advanced age (≥65 years) is positively associated with adherence to prescribed drug regimens (Billups, Malone, & Carter, 2000). In addition, the number of medical conditions, the prescribed medications patients are receiving and their frequency of administration were positively associated with medication adherence (Billups et al., 2000; MacLaughlin et al., 2005). Furthermore, patient satisfaction with care may affect their adherence to medications (Dang, Westbrook, Black, Rodriguez-Barradas, & Giordano, 2013; Krousel-Wood, Muntner, Islam, Morisky, & Webber, 2009). Another important aspect of medication use, patients’ satisfaction with their treatment regimens, was studied recently in a sample of patients with hypertension (HTN), and found to have a positive association with patients’ adherence to their treatment regimens. Patients who were overall satisfied with their prescribed medications’ effectiveness and convenience were more likely to be adherent to their treatment regimens (Sa’ed et al., 2013). In addition, health related quality of life (HRQoL) was also associated with medication adherence. Elderly patients with HTN and poor HRQoL scores have reported low adherence levels to their antihypertensive

Figure 2-2. Factors influencing medication adherence.

Source(s): Gellad, Grenard, & Marcum, A Systematic Review of Barriers to Medication adherence in the Elderly: Looking Beyond Cost and Regimen Complexity. The American

Journal of Geriatric Pharmacotherapy 2011 Feb; 9(1): 11-23.

MacLaughlin et al, Assessing Medication Adherence in the Elderly: which Tools to Use in Clinical Practice? Drugs Aging 2005; 22(3):231-255.

Sa’ed, Al-Jabi, Sweileh, Morisky, Relationship of treatment satisfaction to medication adherence: findings from a cross-sectional survey among hypertensive patients in Palestine. Health and Quality of life Outcomes 2013 Nov; 11(1):191.

The importance of medication adherence stems from the fact that poor medication adherence has been linked to high healthcare costs in comparison to higher levels of adherence which were associated with lower healthcare costs. This is particularly true among patients with chronic medical conditions that can lead to untoward consequences if left uncontrolled (Pittman, Tao, Chen, & Stettin, 2010; Sokol, McGuigan, Verbrugge, & Epstein, 2005). HTN is one of the well-known preventable causes of cardiovascular disease morbidity and mortality. The utilization of antihypertensive medications has been found to reduce the risk of both coronary heart disease (CHD) and stroke by 34% and 21%, respectively (Mazzaglia et al., 2009). Patients with poor adherence to

antihypertensive medications were at higher risk of all-cause mortality, stroke, and acute myocardial infarction (Esposti et al., 2011). Only 51% of the U.S. hypertensive

population are considered adherent to their prescribed medications (WHO). Achieving an acceptable level of adherence (>80%) entails an open and honest relationship between patients and their physicians.

Medication adherence measures can fall into two different categories: direct and indirect measurements (Fairman & Matheral, 2000; Farmer, 1999). Direct measurement of medication adherence can be done through directly measuring the drug concentration in the patients’ blood stream. It can also be done by observing patients and making sure that they swallow their pills and documenting that afterwards and by healthcare providers administering the medication to patients intravenously (IV), or intramuscularly (IM) and documenting the administration. Although direct measurement of adherence is considered the most reliable method of measuring adherence, this is impractical, uncommon, and rarely used. The indirect measurement of adherence are more commonly used and include medication monitoring (electronic monitoring, pills counts), self-report measures (diaries, surveys, and interviews), and prescription claims data (length of therapy,

treatment gaps, medication possession ratio [MPR], and days of coverage) (Fairman & Matheral, 2000; MacLaughlin et al., 2005).

Although there are several methods for measuring medication adherence and each one of them has its own advantages and limitations, no one measure of the

aforementioned methods is perfect (Fairman & Matheral, 2000). The advantage of self- report measures over other medication adherence methods is that they provide the reason for non-adherence from patients’ perspective (Fairman & Matheral, 2000; Lavsa,

Holzworth, & Ansani, 2010). Self-report measures and scales have differing attributes such as the administration time, reliability, specificity and sensitivity, validity, and their ability to detect barriers to medication adherence. The new and commonly used self- report medication adherence scale is the 8-item Morisky Medication Adherence Scale (MMAS-8). This scale was validated across a wide spectrum of clinical conditions with both high sensitivity (93%) and specificity (53%) towards detecting those with poor blood pressure control as well as high reliability (α=0.8) (Lavsa et al., 2010; Morisky, Ang, Krousel-Wood, & Ward, 2008). The original 4-items of the Morisky Medication Adherence Scale (MMAS-4) is a validated shorter version of the MMAS-8, but has lower internal consistency reliability (α=0.61), sensitivity (81%), and specificity (44%) in patients with HTN (Lavsa et al., 2010). Brief Medication Questionnaire (BMQ), Self- efficacy for Appropriate Medication Use Scale (SEAMS), and Medication Adherence

Rating Scale (MARS) are widely used questionnaires that assess medication adherence in multiple patient populations. The BMQ, SEAMS, and MARS have limited

generalizability and lower reliability in comparison with MMAS-8 (Lavsa et al., 2010).