**1. Introduction**

Chronic obstructive pulmonary disease (COPD) is a major public health problem for both industrialised and developing countries (Viegi et al., 2001). The prevalence of COPD is increasing worldwide, resulting in a substantial economic burden, including direct and indirect health-care costs (Chapman et al., 2006).

Non-adherence in COPD is common and poses a significant barrier to optimal disease management. According to the World Health Organization (WHO), adherence to long-term therapies averages only 50% (WHO, 2003). Patient adherence in chronic diseases can result in poor health outcomes and increased health-care expenditures (WHO, 2003). Discontinuation of COPD therapy contributes to increasing the frequency of exacerbations, the number of hospitalisations and the mortality rate (Bourbeau & Bartlett, 2008; Regueiro et al., 1998; Vestbo et al., 2011).

Clinical trials may overestimate the level of adherence to medication regimens. Adherence rates in clinical trials have been expected to be approximately 70%–90% among patients with COPD (Kesten et al., 2000; van Grunsven et al., 2000; Rand et al., 1995). In clinical practice, these rates are only in the range of 20%–60% (Agh et al., 2011; Bosley et al., 1994; Dolce et al., 1991; Krigsman et al., 2007a). This difference reflects the fact that patient adherence may be an important explanatory factor of the difference between the efficacy of treatment under experimental conditions and the real-world effectiveness of the treatment (Revicki & Frank, 1999).

Non-adherence in patients with COPD has a number of causes, including factors related to the characteristics of the patient, the disease, the therapies and the health-care provider– patient relationship (Baiardini et al., 2009; Restrepo et al., 2008; WHO, 2003). Physicians should understand the factors and the strategies that facilitate adherence to improve the effectiveness of the therapy.

The goals of this chapter are as follows: to highlight the importance of adherence in the management of COPD; to introduce the reader to the concepts of adherence, compliance and persistence; to address different methods of measuring adherence; to identify factors related to adherence; and to emphasise strategies to enhance adherence in patients with COPD.

Adherence to Therapy in Chronic Obstructive Pulmonary Disease 277

*A* x x x x x x x 120 no *B* x x x x x x x x 180 yes *C* x x x x x x 60 no

(following diets, executing lifestyle changes, etc.) as well. Explanation of adherence by the WHO also reflects this concept. The WHO definition of adherence is the following: "the extent to which a person's behaviour—taking medication, following a diet, and/or executing lifestyle changes—corresponds with agreed recommendations from a health-care provider" (WHO, 2003). This definition accurately highlights the importance of the patient's active role in their own health-care, which emphasises that the relationship between the patient and the health-care provider should be based on a partnership, instead of a one-

Recently, medication adherence has become the preferred term instead of medication compliance. The primary difference between compliance and adherence is that compliance reflects the patient as a passive recipient of medical advice. Furthermore, compliance has also been viewed as a judgmental term when applied to patient behaviour. Thus,

Most studies in adherence research have focused on medication-taking behaviour. Therefore, the following is a brief overview of the methodology of the assessment of medication adherence in COPD. There are a number of ways to assess adherence; nevertheless, there is not a gold standard because each method has strengths and limitations

The easiest way to assess medication adherence within clinical settings is to collect information from the patient themselves through questionnaires or patient diaries (Agh et al., 2011; Dolce et al., 1991; George et al., 2005, 2006a; Laforest et al., 2010). However, it should be mentioned that self-reporting methods may overestimate a patient's drug-taking behaviour (Dompleing et al., 1992; Rand et al., 1992, 1995). Using postal administration can help to obtain data that are more objective because patients are normally intimidated by their health-care providers and tend to give them the expected answers (Agh et al., 2011). Another commonly used method is the analysis of electronic pharmacy records (Breekveldt-Postma et al., 2007; Cramre et al., 2007; Jung et al., 2009). Retrospective database analysis is rapid and inexpensive. Nevertheless, this approach may also be inaccurate. It evaluates the prescriptions written by physicians or the prescriptions filled by patients, but not the

medication adherence will be the preferred term from this point forward.

**Days persistent** (gap: 30 days)\* **Persisted 180 days\*\***

(1 month = 30 days)

**Patients Months** 

sided paternal relationship.

medication intake directly.

(Table 3).

**2.2 Methods of measuring adherence** 

\*: Patients persisted an average of 120 days ((120+180+60)/3) \*\*: 33% (1/3) of the patients were persistent for 180 days │x│: medication supplied,││: medication not supplied Table 2. Calculation of medication persistence
