Factors behind poor blood pressure treatment control

Furthermore, the reasons for poor BP control also vary between individuals and depend on the situation. However, evidence suggests that poor medication adherence and clinical inertia are the two most important reasons behind the failure in achieving good BP control in hypertensive patients (13-16,103). These factors are introduced in the following chapters.

2.7.2.1 Poor medication adherence

Adherence to long-term medications is a large-scale problem worldwide. It is estimated that adherence to long-term therapies for chronic illnesses is, on average, 50% in developed countries and is even lower in developing countries.

(13)

Furthermore, it is commonly agreed that in hypertension, the most important factor attributable to failure in BP control is poor medication adherence (13,103).

Poor medication adherence is strongly associated with insufficient BP control and poor health outcomes, even though some studies show contradictory results regarding health outcomes (104-106).

Non-adherence to medication can be divided into three types: 1) non-initiation (primary non-adherence), 2) short persistence and 3) non-execution of the dosing regimen (106,107).

Regarding non-initiation of medication (primary non-adherence), Fischer et al.

studied 82,245 electronic prescriptions for new medications in the USA mainly in primary care settings, and found that 28.4% of patients were primarily non-adherent to new antihypertensive medication (i.e. patient did not fill new

prescription.), which was average compared to other drug classes (108). Blaschke et al. studied 36,907 patients in 95 studies with oral medication presciptions for one of a variety of medical conditions and found 4% primary non-adherence rate (107).

Short persistence for antihypertensive medication is an even more common phenomenon and accounts for the largest fall in adherence to medications (107).

Monane et al. studied hypertensive patients in the USA in outpatient settings and found that during the first treatment year, the average hypertensive patient had antihypertensive medication available only 43% of the time and 80% of patients did not achieve a good compliance level, defined as a medication possession of 80% of the time or more (109). Bloom et al. and Vrijens et al. found in separate studies, the former conducted in the USA outpatient settings and the latter combining data from 21 phase IV clinical studies from different countries, that every other hypertensive patient discontinued their antihypertensive medication during the first treatment year (110,111). In a 2012 meta-analysis of 376,162 patients and 20 studies carried out in developed countries with follow-up period ranging from 12 to 120 months, Naderi et al. concluded that every other patient on antihypertensive medication or other primary prevention drug does not take medication as prescribed (112). Adherence rates were 50% for primary and 66%

for the secondary prevention of coronary artery disease and the overall adherence rate was 57% (112). The results of the literature reviewed by Burnier et al. are even more disappointing, as they conclude that non-persistence continues to reduce the proportion of patients still engaged in taking medication for at least 5 years after the onset of medication, by which time only a small minority (10 – 15%) are still adherent to the antihypertensive medication (106).

The third type of non-adherence is non-execution of the dosing regimen.

Vrijens et al. concluded that on any given day, hypertensive patients still engaged in drug treatment left out about 10% of the scheduled doses, of which 42% were single day omissions and 43% were part of an omission lasting three or more days (“drug holidays”) (111). Blaschke et al. estimated the proportion of omissions to be 8 – 10% on any given day (107).

2.7.2.2 Clinical inertia and health care system-related barriers

In 2001, Phillips introduced the term “clinical inertia” to describe different kinds of professional-related barriers to succesful treatment, defining it as “a failure of health care providers to initiate or intensify therapy according to current

guidelines” (113). Indeed, research shows that non-adherence to therapy does not only apply to patients, but physicians also tend to lack adherence to hypertension guidelines, be satisfied with inadequate BP control and overestimate patients’ BP control (14-16). A recent study in ambulatory care units in the USA found that in 14,064 visits by hypertensive adults with BP >140/90 mmHg, treatment

intensification occurred in only 17% of primary care visits and medication initiation in newly diagnosed hypertensive patients in only 26% of visits (114).

The reasons for clinical inertia are manifold. According to Phillips, clinical inertia is “due to at least three problems: overestimation of care provided; use of ‘soft’

reasons to avoid intensification of therapy; and lack of education, training, and practice organization aimed at achieving therapeutic goals” (113). Research on this area has focused a lot on the different factors that are associated with clinical inertia. According to Milman et al., they can be divided into patient characteristics, physician characteristics and factors that impact the patient-provider interaction (115).

Patient characteristics include multiple comorbidities (especially psychiatric conditions), older age, lower life expectancy and patients who are “near-target”

(115). The same characteristics (and being female, in addition) were found to be associated with a lower likelihood of treatment intensification also in a study by Mu & Mukamal (114). Interestingly, Mu & Mukamal found that treatment

intensification was more likely with higher levels of measured BP, but prevalence among patient visits with an SBP ≥160 mmHg was still only 25% (compared to 11%

among all patient visits with an SBP ≥120 mmHg) (114).

Physician characteristics include high patient volume, time constraints, lack of knowledge about BP goals, as well as personal characteristics such as differences in risk tolerance and decision-making (115). Lack of adherence to hypertension

guidelines, satisfaction with inadequate BP control, overestimation of patients’ BP control, use of ‘soft’ reasons to avoid intensification of therapy and lack of

education, skills or motivation, as well as old habits, misleading beliefs, social- or professional role-related barriers, difficulties in priority setting, lack of trust in evidence and lack of belief in capability can also be counted as physician characteristics associated with clinical inertia (14,15,113,116,117). It is not uncommon for a health care provider to disagree with guideline

recommendations (117). In a systematic review and meta-analysis of patient and health care provider barriers to succesful hypertension treatment, Khatib et al.

identified disagreement with clinical guidelines as the most common barrier among health care providers in quantitative studies (117).

Factors that impact the patient-provider interaction and health care system-related barriers for good BP control include time constraints, lack of training and feedback given to health care providers, as well as lack of organizational

prioritization and lack of availability or other resources (113,117).