Self‐blood pressure monitoring as a tool to increase hypertension awareness, adherence to antihypertensive therapy, and blood pressure control

For many years, casual blood pressure (BP) taken by a sphygmomanometer in the clinic or at the physician's office has been used as the standard method for diagnosing hypertension. Even if such measurement has been the cornerstone on which our understanding of the consequences of hypertension is based, there is a huge and very consistent body of evidence indicating that casual measurements of BP may provide a very unreliable index for the evaluation of hypertension because of their variability.

The two alternative ways of measuring BP that have been most commonly used are measurements made at home by the patient himself (home or self‐BP monitoring—SBPM) and measurements by ambulatory blood pressure recorders.1

Results obtained by these methods have given closer correlation with a variety of measures of hypertensive end‐organ complications than casual or office BP.1, 2, 3 Furthermore, the prognostic studies indicate that BP measurements performed in “out‐of‐office” settings (using both home and ambulatory monitoring) are superior to office BP in predicting cardiovascular morbidity and mortality.1, 4

Moreover, SBPM is a practical, reproducible, easy‐to‐learn, and economical way to reduce some of the pitfalls of relying exclusively on readings taken in the clinic. Most current self‐monitoring electronic devices are relatively cheap, simple to operate, will remove observer bias, and allow for multiple measurements in a short time. In addition, it may be possible to reduce or to eliminate the “white‐coat effect” that influences office BP readings.1

It has been known since the classic study of Ayman and Goldshine in 1940 that home recordings are generally lower than office readings.5 These authors, working in Boston at Beth Israel Hospital, reasoned that the home environment might be more conducive to obtaining BP readings without the stress associated with an office or clinic visit, recognizing that measurements of pressure at home, outside the clinic, might provide a more accurate assessment of patients' usual BP. Clearly, these authors had identified what is now called “white‐coat” or clinic hypertension, although they did not coin these terms. They were the first to propose the concept of “self‐BP measurement”, pioneeringly suggesting that home BP monitoring was useful for (a) instructing the patients about their chronic diseases, (b) teaching physicians about the natural course of the disease and about factors that affect the disease, (c) learning the prognosis of disease, and (d) increasing the precision of determining the effectiveness of treatment.5

Nowadays, progress in technology has offered novel approaches to telemonitoring of BP values measured at a patient's home. Blood pressure telemonitoring (BPT) is a telehealth strategy that allows remote data transmission of BP and other information on patients' health status from their dwellings or from a community setting to the doctor's office or the hospital.6, 7

For all the above reasons, the use of HBPM is recommended by several national and international guidelines for the management of hypertension, in order to obtain a more representative estimate of the average BP than casual and incidental reading at the clinic or at the office.8, 9, 10, 11, 12 For the most part, the recommendations from the various organizations are similar, as outlined below, although there are some minor differences.

1. The levels of SBPM considered normal by the majority of the guidelines are a BP of <135 mm Hg systolic and 85 mm Hg diastolic.8, 9, 10, 11, 12 The 2017 US guidelines recommend a threshold at 130/80 mm Hg (office or home BP) for confirmation of uncontrolled hypertension, which is in line with normal home BP according to the European recommendations.11, 12

2. Validated automated upper‐arm cuff devices with automated storage and averaging of readings should be used.

3. The indications for SBPM include the assessment of white‐coat hypertension and the monitoring of effective BP control in conjunction with office BP measurement.

4. The success of SBPM depends on adequate patient education on the use of BP monitors and in patient training in proper measurement technique. SBPM should be done in the morning and evening before taking medication.

The home blood pressure measurements should be performed for at least 3 days and preferably for 6‐7 consecutive days with exclusion of the first day. The readings so obtained should be averaged to provide values for decision making.8, 9, 10, 11, 12

While emphasizing the above advantages of SBP, it is important to acknowledge that SBPM is usually only carried out during periods of relative relaxation and is therefore unlikely to be able to capture what happens during stressful periods. Similarly, it cannot be used to obtain information on BP levels during nighttime sleep, which have shown to be of major clinical relevance because of their demonstrated prognostic value.8, 9, 10, 11, 12 However, in recent years validated, memory‐equipped devices have been designed that can be programmed to provide nocturnal BP recordings similar to those obtained with 24‐hour ABPM.1, 13

It is likely that the use of self‐monitoring for the routine evaluation of hypertensive patients will continue to grow in the foreseeable future. This trend may be viewed as part of a general movement in which patients are playing an increasingly important role in the management of their health. In the past, the paternalistic medical model assumed that only physicians knew how to take BP, and the patient's only duty was to follow orders.

Hypertension is a chronic condition, and its ill effects on cardiovascular health often develop slowly. Therefore, systems to provide consistent surveillance and to assist patients in maintaining blood pressure control over time are critical to reducing mortality and morbidity.

Poor adherence to therapy has been recognized as one of the most important factors contributing to uncontrolled hypertension. By encouraging patients to become actively involved in their care, and by positively affecting their perceptions about the management of hypertension, SBPM offers the possibility to improve patient's compliance and adherence to lifestyle changes and/or medical treatment.1 A number of randomized controlled trials have also provided evidence of the benefits and cost‐effectiveness of programs based on implementation of home‐based BP telemonitoring.6, 7 During the diagnostic assessment of hypertension, it reduces misclassification of BP levels by identifying white‐coat hypertension and masked hypertension, and in treated hypertensive patients, telemonitoring allows a better assessment of the BP response to antihypertensive treatment and may help improving therapeutic decisions.6, 7

Besides, provided that the practitioner has more information available to make clinical decisions, SBPM also helps to reduce therapeutic inertia. In turn, all of this may potentially increase rates of BP control. Indeed, there is also some evidence that the regular use of SBPM is associated with a small but significant BP reduction compared with usual care. However, there is a considerable heterogeneity between studies and most current evidence is based on studies of relatively short duration (<12 months). Moreover, it is not enough clear whether the use of SBPM needs to be combined with additional support (education, counseling, telemedicine, or other measures) to facilitate adherence to lifestyle measures and medication.1, 10

In the current issue of Journal of Clinical Hypertension, Jo and coll14 reported the results of an observational prospective study, assessing the impact of a 3‐month self‐BP monitoring program on BP control, compliance to treatment, and awareness of hypertension. The study population consisted of a large cohort of 7751 hypertensive patients attending outpatient clinics of private and university hospital in Korea.14

The authors found that after the 3‐month period of SBPM, BP significantly decreased, the number of patients with controlled BP increased, and adherence to drug therapy and patients’ perception of BP improved.14

Even if more than 50 previous investigations and some meta‐analyses (Table 1)15, 16, 17, 18, 19, 20 explored a similar issue, the study of Jo et al is the one of the largest and the unique studies evaluating also the effect of SBPM on perception and attitude on BP of patients and physicians.14

Table 1.

Meta‐analyses investigating the effect of self‐blood pressure monitoring programs on blood pressure reduction

Study (Author)ref.	Year	No of studies included (SBP/DBP)	No of participants (SBP/DBP)	BP reduction (mm Hg)
				Systolic BP	Diastolic BP
Cappuccio F15	1996	13/16	2120/2568	4.2a	2.4 a
Glynn LN16	2010	12/14	2492/2598	2.53	1.81
Bray EP17	2010	20/23	5898/6038	3.82	1.45
Agarwal R18	2011	37/37	9446	2.63	1.68
Uhlig K 19	2013	8/9	1471/1539	3.9b	2.4b
Tucker KL20	2017	15/15	6300	3.24 c	1.50 c

Abbreviations: DBP, diastolic blood pressure; SBP, systolic blood pressure.

^a2.2/1.9 mm Hg, when allowing for publication bias.

^bAssessed at 6 mo; at 12 mo, the BP reductions were not statistically significant (1.5/0.8 mm Hg).

^cIndividual data meta‐analysis.

From a prognostic point of view, the most important finding of this paper is represented by the improvement of BP control rate after 3‐month period of SBPM. This result may be largely driven by the raised adherence to antihypertensive therapy which in turn may be explained, at least in part, by the improved awareness of the importance of BP control in both patients and physicians.14

The results of this interesting study need to be interpreted with caution, because of some limitations. Beside the intrinsic weakness due to its observational nature, the inability to account for some potentially important confounding factors, such as drug antihypertensive therapy, intensification of treatment and lifestyle factors, the nonrandomized inclusion of the participants, the absence of information about the true home BP measurement of the patients, the nonobjective estimation of the adherence to antihypertensive prescriptions, based on the frequency of drug skipping reported by the patients, and the short duration of the study are other drawbacks of this paper.14

In conclusion, the findings of the study of Jo et al support the concept that adoption and implementation of SBPM in clinical practice may give a significant contribution to BP control, because it is associated with greater adherence to pharmacological therapy and awareness of hypertensive status, when compared to conventional BP monitoring. Further studies, with a longer duration and a randomized controlled design, are warranted to validate these results.

CONFLICT OF INTEREST

The authors have no conflict of interest to declare.