The reach and limitations of medication treatment adherence for - PDF document

The reach and limitations of medication treatment adherence for hypertension control among patients of the Family Health Strategy: a case study for a midsize city in Brazil Authors Gilvan Guedes, Kenya Noronha, Monica Viegas Andrade, Julia Calazans, Carlos Alberto Dias, Djenane Oliveira, Kirla Detoni, PRELIMINARY VERSION PLEASE DO NOT QUOTE Abstract Although the Family Health Strategy (FHS) has increased the access to public health services in Brazil, some health outcomes among its users are still below the desired standards. One advocated cause for this mismatch is treatment adherence. Many studies suggest that increased levels of medication treatment adherence promote better health outcomes, reducing burden on patients and pressure on the health system. Some scholars, however, argue that the ability of adherence to correctly improve health depends on a more subtle set of variables, such as absence of drug interaction, drug regimen complexity; patients perceived experience with the drugs, absence of clinical inertia, and a comprehensive system of pharmaceutical care that facilities access and compliance. The understanding of the relation between treatment adherence and health outcomes, including its reach and limitations, is key for improving patients’ well -being, especially for symptomless chronic diseases such as hypertension. Based on novel data for patients with hypertension, users of the public primary care system in a mid-size city in Brazil, we analyze: (1) the extent to which medication treatment adherence can improve BP (BP) control ( reach ), and (2) the likely causes for why a large group of highly adhered patients find themselves with high levels of BP ( limitation ). Our data come from a probabilistic, stratified sample of 641 FHS users, 40 years and older, under drug treatment for hypertension for at least 6 months, interviewed in 2014 and followed up in 2016. To provide insights on the reach of treatment adherence we make use of a combination of descriptive statistics and structural equation modeling applied to the 2014 data. The limitations of treatment adherence and their likely causes were addressed using the longitudinal data for those highly adhered in the baseline survey, both within and out of the BP goal. Detailed information on patients' drug use and dosage was collected, as well as their personal experience with the drugs. Our results suggest that adherence is important for BP control, even after accounting for mediation effects of motivational drivers, physical activities, and smoking habits. However, the association is somewhat weak since a large proportion of the adhered patients are out of the BP goal. The longitudinal data will allow us to address the limitations of drug treatment adherence. Altogether, our findings support the importance of the public provision of health services, but highlight the need for the inclusion of persistent pharmaceutical care practices for treatment adherence to reach its full potential. Keywords: hypertension, drug treatment adherence, public primary care system, Brazil

1. Introduction Hypertension is an important risk factor for coronary heart disease and stroke. The 2008 World Health Organization data show a global prevalence of hypertension at around 40% among adults 25 years and over, corresponding to 7.5 million deaths (12.8%) and 57 million (3.7%) disability adjusted life years (DALYS). Studies in Brazil estimate that between 14% and 36% of adults are diagnosed with hypertension (Lessa et al 2006, Nunes-Filho et al 2007, Duncan et al 2012). Data from the Brazilian Ministry of Health reveal that in 2012 alone 154,919 hospitalizations related to hypertension were registered, leading to non-negligible costs to the Public Health System (SUS, in Portuguese). The high prevalence and low rates of blood pressure (BP) control make hypertension one of the main risk factors for kidney, cardiovascular, and cerebrovascular diseases (Miranzi et al 2008, James et al 2014). Current anti-hypertensive drugs are cost-effective, although BP control therapy may be costly for patients (Heisler et al 2008, Bernard et al 2014). In Brazil, the provision of anti-hypertensive medication for free or at a very low cost by the Public Health System through the Popular Pharmacy Program eliminates most financial barriers to medication. Thus, why so many individuals with hypertension have persistent high BP despite the large and relatively cheap availability of effective anti-hypertensive medication? Three main explanations are given in the literature: clinical inertia (Heisler et al 2008), drug interactions due to the pharmacological regimen complexity (MacDonell et al 2013, Rajpura and Nayak 2014), and poor medication treatment adherence (Krousel-Wood et al 2004). Clinical inertia refers to the failure from providers to properly increase medication dose or the number of drugs in response to persistently high BP (Giugliano and Esposito 2011, Gil-Guillen et al 2010). Studies suggest that it is mainly driven by a safeguard in clinical practice (Giugliano and Esposito 2011) and by limited information available for the providers on the history of patients’ treatment adherence (Heisler et al 2008). The second driver, polypharmacy, is also likely to result in low levels of efficacy to control BP, especially when drug interactions request undetected drug intensification (Heisler et al 2008). Treatment adherence, as the third and most important factor for BP control, is the cause of up to 50% of treatment failures and is associated with disease progression, avoidable hospitalizations, disability, and death (Stephenson 1999, Sokol et al 2005). Due to its importance for BP control, ways to leverage medication treatment adherence has been subjec t of research since the 1960’ s (DiMatteo et al 2002). Scholars, however, have been increasingly recognizing the limitations of adherence to pharmacological therapy alone to fight raised BP. A major challenge in addressing the association between adherence and BP control is that most of their drivers are shared. For this reason, understanding what causes persistent high BP leads to the understanding of the causes of poor treatment adherence. Clinical inertia, on the providers ’ side, and patients’ experience with the medication (including beliefs on necessity and adverse effects), on the users ’ side, are recognized to render poor levels of adherence (Heisler et al 2008, Riegel and Dickson 2016, Molloy et al 2014, Rajpura and Nayak 2014, Clifford et al 2008, Horne Weinman 1999).