Interventions used to improve control of blood pressure in patients with hypertension

Background

High blood pressure (hypertension) is an important public health problem in terms of associated stroke and cardiovascular events. It is mostly of unknown aetiology, is easy to diagnose and is readily preventable by blood pressure reduction. Extensive epidemiological data have strengthened the well‐recognised relationship between blood pressure and cardiovascular disease risk and have confirmed the importance of systolic BP as a determinant of risk (Prospective Studies Collaboration 2002). Evidence from randomized trials has shown that effective drug treatment reduces the risk of cardiovascular morbidity and mortality (Collins 1994; Gueyffier 1999). However, there is ongoing concern that the benefits demonstrated in randomized trials of antihypertensive drug treatment are not implemented in everyday clinical practice (Burnier 2002). Community‐based studies throughout the world show that blood pressure goals are achieved in only 25 to 40% of the patients who take antihypertensive drug treatment (Burnier 2002; Hyman 2001; Chobanian 2001; Smith 1990), a situation that has remained unchanged for the last 30 years (Wilber 1972).

The quality of care patients with hypertension receive from health professionals has a clear impact on their risk of suffering a cardiovascular event. Observational studies in the UK have shown that inadequate control of blood pressure and poor follow‐up is associated with a significant risk of stroke and avoidable vascular deaths (Du 1997; Payne 1993). In terms of the process of care that hypertensive patients receive, characteristics of the patient, health professional and the healthcare system in which they are given their medical care have been implicated in poor blood pressure control. Lack of adherence to medication and not having a primary care physician were associated with poor blood pressure control in a US study (Shea 1992). More recent studies have shown that frequent contact with health care professionals does not guarantee better blood pressure control unless there is more vigorous use of antihypertensive drugs (Hyman 2001; Berlowitz 1998), and that individual practitioners vary substantially in their clinical performance when managing hypertension in the community (Frijling 2001). These observations have led some commentators to suggest that poor control of blood pressure in the community may be due to ineffective management and inadequate practice organisation, described jointly as "clinical inertia" (Phillips 2001). Use of self monitoring of blood pressure by patients and professionals has gained popularity and is now recommended in certain patients in some national and international guidelines. A recent meta‐analysis of randomised trials on the subject did suggest a benefit in terms of mean blood pressure and blood pressure control (Cappuccio 2004).

Whilst there is a strong evidence‐base for the benefits of antihypertensive drug therapy (Collins 1994; Blood 2000; Staessen 2001), there is little clear evidence as to how care for hypertensive patients should be organized and delivered in the community to help improve blood pressure control. This systematic review aims to update and build upon previous reviews (Ebrahim 1998; Fahey 2006), to summarize the evidence from randomized controlled trials that evaluate different models of care that have been used to improve the control and follow‐up of patients with hypertension.

Objectives

The objectives of this review are to:

(1) Evaluate which models of care are effective in improving "control" of high blood pressure;

(2) Evaluate the effectiveness of reminders on improving the follow‐up of patients with hypertension.

Methods

Results

Discussion

Key findings from this review 
 The main finding from this systematic review is to a large extent dominated by the findings from the largest RCT, the HDFP study (Hypertension 1979; Hypertension 1979a; Hypertension 1982). Though partly intended as a trial to assess the value of systematic identification of hypertensive patients (Davis 2001), the key ingredients of how patients with established hypertension and taking antihypertensive drug treatment were managed‐ free care, registration, recall and regular review in tandem with a rigorous stepped care approach to antihypertensive drug treatment‐ should be emphasized as this multi‐faceted intervention was effective in terms of reaching blood pressure goals and reducing all‐cause mortality. It is interesting to note that a two‐year post trial surveillance study showed that blood pressure control was attenuated when the stepped‐care arm of the study was discontinued. This lack of control was associated with a decline in the use of antihypertensive medication (Hypertension 1986).

The other significant finding from this review is that self‐monitoring was associated with a decline in systolic blood pressure (2.5 mmHg) and diastolic blood pressure (1.8 mmHg). Although this blood pressure reduction does not appear substantial in clinical terms, it appears to be nonetheless a useful adjunct to care and is likely to lead to a reduction in cardiovascular events. Further evaluation in larger RCTs and prospective studies including cardiovascular outcomes are warranted. Other interventions assessed in this systematic review did not produce clear results. None of the other interventions were associated with large, clinically important, reductions in either systolic or diastolic pressure, see MetaView. Education alone, directed either to patients or health professionals appears unlikely to influence control of blood pressure as a single intervention, as results were highly heterogeneous or of marginal clinical importance. Use of health care professionals such as nurses and pharmacists, though producing significantly heterogeneous results, did have mainly favourable effects, and merit further definitive evaluation in larger RCTs. Lastly, reminders (postal, computer or telephone based) were associated with an improvement in the follow‐up and control of patients with hypertension but produced heterogeneous results in terms of systolic and diastolic blood pressure. This finding is consistent with the organisational structure of the HDFP study and re‐iterates the importance of systematic recall systems when organising care for hypertensive patients.

Context of other studies 
 There are elements identified from this review that appear to be associated with improved blood pressure control and are consistent with findings from observational studies and previous systematic reviews. In a large community‐based study, patients who received intensive antihypertensive drug therapy were significantly more likely to have reduced systolic blood pressure of 6.3 mmHg compared to an increase of 4.8 mmHg in those who received less intensive antihypertensive drug therapy (Berlowitz 1998). A more recent observational study showed that antihypertensive drug therapy was initiated or changed in only 38% of episodes of care, despite documented uncontrolled hypertension for at least six months (Davis 2001; Oliveria 2002). Lack of practice organisation is associated with a failure to achieve treatment surrogate goals in hypertension, diabetes and secondary prevention of coronary heart disease (Phillips 2001). A recent systematic review of self monitoring also produced similar findings of modest but potentially important benefit in systolic and diastolic blood pressure (Cappuccio 2004 errat). This is important in light of the fact that self monitoring is now practiced by up to two thirds of the hypertension population in the US and Europe (Pickering 2008). We have found substantially more RCT evidence in terms of hypertension management than a recent systematic review that examined interventions used in disease management programmes for patients with chronic illness (Weingarten 2002). In that review, eight hypertension‐related RCTs were cited, which provided some evidence of benefit in terms of education directed at the patient and provider (health professional) (Weingarten 2002). In this systematic review of 72 RCTs, the subset of RCTs where the intervention was directed at the patient (n=20) or physician (n=10) does not support this finding, showing no clinically important evidence for patient or health professional education as an effective implementation strategy in the management of hypertension.

Study limitations 
 There are several shortcomings that need to be highlighted in this systematic review. The HDFP study was designed as an intervention that would identify newly diagnosed hypertensive patients and then start or modify antihypertensive treatment in those with untreated as well as uncontrolled hypertension (Davis 2001). A consequence of this study design is that a differential number of people were receiving antihypertensive drug treatment in the two arms. At follow‐up in year five, 81.2% of patients in the stepped care arm were taking antihypertensive medication compared to 64.2% of patients in the referred care arm (see details on included studies). So though it appears that the systematic follow‐up and stepped care approach in HDFP is an important element in effective clinical care and prompts rigorous antihypertensive drug treatment, it is not possible to distinguish between the independent effect of these interventions on blood pressure control. Several other RCTs included both treated and untreated hypertensive patients and had differential rates of antihypertensive drug prescribing (Vetter 2000; Midanik 1991; Rudd 2004; Ornstein 2004; Contreras 2005), with rates of prescribing at higher levels in the intervention arm at follow‐up. Secondly, many RCTs contained multi‐faceted interventions that did not fit into a single intervention category. For example, several RCTs that were included under categories of patient education, physician education, health professional led care and organisation of care also incorporated some form of reminder intervention such as postal reminders or computer generated feedback (Dickinson 1981; Hamilton 1993; Hawkins 1979; Takala 1979; Takala 1983). Consequently, it has been difficult to attribute how far single elements that make up complex interventions exert their independent effect on blood pressure control. In terms of self monitoring, it is well established that "office" blood pressure readings are around 10/5mmHg higher when compared to ambulatory or self monitored readings (Staessen 1997; Staessen 2004; Williams 2004). Several of the RCTs did not make any recommendations about the need for adjustment of target blood pressure readings when self monitoring was the intervention being assessed, nor did they appear to anticipate lower blood pressure readings in the self monitoring group (Bailey 1998; Johnson 1978; Pierce 1984; Baqu‚Äö 2005). This may have attenuated the impact of self monitoring on blood pressure control because of failure to intensify treatment. Poor adherence to therapy is thought to be associated with poor control of blood pressure (Shea 1992) and medication adherence in hypertension is estimated to be only around 50% to 70% (Ebrahim 1998). Yet only a few trials examined the relationship between adherence to medication and control of blood pressure (Haynes 1976; Johnson 1978; Sackett 1975; Schroeder 2005; Sookaneknun 2004; de Castro 2006; Wetzels 2007) despite the significant influence that adherence may have on blood pressure control. Future studies will need to be designed to assess the relationship between poor adherence and poor response to antihypertensive drugs in patients with good adherence. Cluster design was used in 14 of the 71 randomized controlled trials that met the inclusion criteria. The majority (8) of these trials correctly adjusted for clustering effect. However, in those six trials that did not, the potential exists for unit of analysis errors. However, sensitivity analysis excluding those studies did not significantly alter our main results. Lastly, not all RCTs reported on the outcomes of blood pressure achieved or blood pressure control. This has meant that the relevant a priori outcomes have not been reported for all included RCTs, and pooling of data from all RCTs has not been possible. Two further trials were identified which were published outside the search dates and thus were not included in the analysis. The first was a 2 × 2 randomized controlled trial with two year follow‐up comparing two self‐management interventions for improving BP control among 636 hypertensive patients in two university‐affiliated primary care clinics (Bosworth 2009). Patients received usual care, a behavioral intervention (bimonthly tailored nurse‐administered telephone intervention targeting hypertension‐related behaviours), home BP monitoring three times weekly, or the behavioral intervention plus home BP monitoring. Combined home BP monitoring and tailored behavioral telephone intervention improved BP control, systolic BP, and diastolic BP at 24 months relative to usual care. The success of this combination of self‐monitoring and nurse‐led care appears to consolidate some of the findings of our review. The second was a randomized controlled trial in 14 community pharmacies in Edmonton, Alberta, Canada, of 227 patients with diabetes who had BPs higher than 130/80 mm Hg on two consecutive visits two weeks apart (McLean 2008). In patients who had diabetes and hypertension that were relatively well controlled, a pharmacist and nurse team based intervention resulted in a clinically important improvement in BP.

Authors' conclusions

What's new

History

Protocol first published: Issue 2, 2002
 Review first published: Issue 1, 2005

Data and analyses

Characteristics of studies

Contributions of authors

All authors contributed to the design, article review, data extraction, analysis and write up of the review.

Sources of support

Declarations of interest

None declared.

New search for studies and content updated (conclusions changed)