Does treatment adherence correlates with health related quality of life? findings from a cross sectional study

The concepts of health-related quality of life (HRQoL) and medication adherence are frequently used in clinical research for assessing pharmaceutical care and treatment outcomes [1]. Adherence to drug treatment usually refers to the extent to which patients follow the instructions of their physician or other health care providers [2]. HRQoL is the assessment of physical, psychological and social dimensions of health that are influenced by an individuals experiences, beliefs, expectations and perceptions [3]. In a broader context, medication adherence is a transitional outcome variable while HRQoL is an ultimate outcome representing conclusions following a course of care [1]. This entails that a change in adherence is likely to occur first, which is subsequently followed by a change in HRQoL while assessing treatment or interventional outcomes [4]. Therefore, it can be predicted that patients who adhere to their treatment regimen should experience improvements in HRQoL and vice versa. Nevertheless, it is not wise to rule out other factors affecting medication adherence and HRQoL. For example, in the case of chronic diseases like diabetes or hypertension, adherence might be positively associated with side effects and perhaps lower HRQoL. On the contrary, for acute diseases, adherence to medication might be associated with a swift advancement in improving HRQoL. It is now known that in terms of quality of life, chronically ill individuals show lower quality of life and are less adherent to their medication [5, 6].

Within this context, hypertension is a chronic disease that requires lifelong treatment. The success of therapy is thereby affected by the impact of the drug regime on the patients well-being [7, 8]. Consequently, comprehensive assessment of therapy must include assessment of medication adherence and HRQoL along with the evaluation of traditional bio-physiological measures. Antihypertensive therapies should be compared for their efficacy in controlling blood pressure and also improving or at least maintaining HRQoL [9]. Regardless of the nature of studies relating HRQoL in hypertension, it is frequently reported that hypertensive patients have decreased HRQoL [10, 11]. In the presence of evidence based guidelines [12, 13], a challenge faced by the healthcare providers is that even in the controlled state, hypertensive patients were reported to have decreased HRQoL [14].

In the current literature, few studies have attempted to measure the association between medication adherence and HRQoL. Moreover, results from such studies provide conflicting results [1, 15–17]. This may be because of the variations in assessing HRQoL and medication adherence, as well as the study population being examined [18]. In addition, more or less, such studies are often produced and reported from developed nations. Considering the unavailability of information from developing countries, the association between medication adherence and HRQoL was examined. The aim of this study was to examine the relationship between adherence and HRQoL in a hypertensive population attending public hospitals in the city of Quetta, Pakistan.

The results from the present study show a weak or negligible negative correlation between medication adherence and HRQoL. The participants were also reported with decreased HRQoL and poor treatment adherence to medications. Similar results were reported in a meta analysis where hypertension patients were reported with decreased HRQoL [10]. In another study among hypertensive patients, lower medication adherence was associated with poor HRQoL in a population based survey in Brazil [14].

With the exception of the negative association, the current study findings agree with those in the literature [1, 16, 26, 27]. However, Carbello et al. concluded that certain HRQoL domains are closely related to medication adherence in an HIV population [28]. These findings were again supported by Takemura and colleagues, who concluded that better adherence is associated with better HRQoL in their study among asthmatic patients in Japan [29].

The negative association between medication adherence and HRQoL is explainable using the theoretical model of Self-Regulation [30]. Interest and involvement of patients in improving one's own health is the key determinant of a successful medical treatment. Medication adherence is an important component of disease state management; however, it is one phase of the entire process. HRQoL, on the other hand, encircles a complex web of psychosocial characteristics that can impact a patients ability to manage their chronic disease and does not depend on a single factor. In the majority of cases, the patient observes their own behaviour and evaluates how this behaviour affects their current health status. Only if the desired results are not realised, a change in personal behaviour is initiated. If the patients are satisfied with the outcomes, they maintain status quo. A weak association from the current study is in line with the recognition that HRQoL is affected by a number of factors and is not limited to medication adherence only.

A possible explanation of this negative association can be attributed to the measurement of medication adherence and HRQoL. Although there is no gold standard for adherence and HRQoL measurement [31, 32], it is always advisable to use a disease/population specific instrument. This can result in a response to small changes in medication adherence and HRQoL and perhaps can give a stronger association. Even though Cote et al. used four different instruments of HRQoL assessment (RAND-12, SF-12, HUI-2 and HUI-3) and the Morisky Medication Adherence Scale (MMAS) for assessing medication adherence, proposed a disease-specific instrument, which is in line with our suggestions [1].

The negative association that was observed here may be linked to the frequency and class of antihypertensive medication used by the patients. The efficacy of antihypertensive agents is unquestionable but certain side effects are always associated with the therapy [33, 34]. Side effects in adherents can be one possible reason for the decreased HRQoL. Moreover, different antihypertensive agents affect HRQoL in a different way. Even medications from the same pharmacological class, with the same efficacy and safety profile, show different impact on HRQoL [7]. For example, a study involving two different calcium channel blockers, nifedipine and amlodipine, concluded that nifedipine had a positive effect on overall quality of life compared with no change in the amlodipine group [35].

In this context, the duration of the disease itself is very important in interpreting the association between medication adherence and HRQoL. Patients who are recently diagnosed with hypertension may experience an increased HRQoL for the first few months of therapy. However, for chronic hypertensive patients, adherence to medication might not improve HRQoL. Subsequently, HRQoL in chronic patients can be observed as maintained but this preservation is never taken as improved by the patients. This is supported by the current study results, where 146 (37.9%) and 124 (32.3%) of the respondents had hypertension for more than five years and within three to five years, respectively, and reported decreased HRQoL.

The current findings revealed that the study cohort was dominated by age group of 2837years (48.3%) and patients with bachelors level of education (40.0%). However, both treatment adherence and HRQoL are multifactor phenomenon and success or failure of therapy and overall health status are not dependent on a single factor [2, 3]. Factors such as gender, low socioeconomic status, prescribed drugs, posology, lack of social support, poor patient provider relationship, cost, forgetfulness, and presence of psychological problems should also be kept in mind and evaluated before coming to a conclusion regarding treatment adherence and its effect on HRQoL.

In general, the weak correlation between medication adherence and HRQoL reflects no apparent relationship. The absence of an association indicates other factors affecting HRQoL during the course of care. Further investigations of the relationship between medication adherence and HRQoL using disease-specific instruments are warranted.

FS and NUH conducted the survey and drafted the initial manuscript. MAH, AAS and AAG designed and supervised the study. MA, HA and MF helped in statistical analysis, interpretation and manuscript revision. All authors read and approved the final manuscript.