Knowledge of blood pressure levels and targets in patients ... - Nature

Journal of Human Hypertension (2005) 19, 769–774 & 2005 Nature Publishing Group All rights reserved 0950-9240/05 $30.00 www.nature.com/jhh

ORIGINAL ARTICLE

Knowledge of blood pressure levels and targets in patients with coronary artery disease in the USA S Cheng1,6, JH Lichtman2, JM Amatruda3, GL Smith4, JA Mattera1, SA Roumanis1 and HM Krumholz1,2,3,5 1

Center for Outcomes Research and Evaluation, Yale-New Haven Health, New Haven, CT, USA; 2Department of Epidemiology and Public Health, Yale University School of Medicine, USA; 3Section of Cardiovascular Medicine, Yale University School of Medicine, USA; 4Department of Internal Medicine, Yale University School of Medicine, USA; 5Robert Wood Johnson Clinical Scholars Program, New Haven, CT, USA

Little is known about patient awareness of nationally recommended blood pressure targets, especially among patients with cardiac disease. To examine this issue, we interviewed 738 patients hospitalized with coronary artery disease to assess their knowledge of their systolic and diastolic blood pressure levels as well as corresponding national targets. We used bivariate and multivariate analyses to determine if any patient demographic or clinical characteristics were associated with blood pressure knowledge. Only 66.1% of patients could recall their own systolic and diastolic blood pressure levels. Only 48.9% of all patients could correctly name targets for these values. Knowledge of target blood pressure levels was particularly poor among patients who were female (odds ratio (OR) 0.69; 95% confidence interval (CI) 0.49–

0.98), aged X60 years (OR 0.70, CI 0.51–0.97), without any college education (OR 0.48, CI 0.35–0.65), without a documented history of hypertension (OR 0.57, CI 0.39– 0.84), and with known diabetes (OR 0.46, CI 0.33–0.66). Patients in the highest risk group, according to Joint National Committee guidelines stratification, were no more knowledgeable about their blood pressure levels and targets than lower risk patients. A significant proportion of patients hospitalized with coronary artery disease do not know their own blood pressure levels or targets. Current blood pressure education efforts appear inadequate, particularly for certain patient subgroups in which hypertension is an important modifiable risk factor. Journal of Human Hypertension (2005) 19, 769–774. doi:10.1038/sj.jhh.1001895; published online 28 July 2005

Keywords: blood pressure; prevention; knowledge; practice guidelines; coronary artery disease

Introduction As many as 65 million adults in the United States have high blood pressure.1–3 National public health campaigns have attempted to increase awareness of high blood pressure with the aim of decreasing its prevalence. Since its inception by the National Heart, Lung, and Blood Institute (NHLBI), the National High Blood Pressure Education Program has implemented numerous patient-based and populationbased approaches to this goal over the last two decades.4–6 First published in 1977 and also sponsored by the NHLBI, the Joint National Committee (JNC) guidelines have specifically recommended that Correspondence: Dr HM Krumholz, Yale University School of Medicine, 333 Cedar St, PO Box 208088, New Haven, CT 065208088, USA. E-mail: [email protected] 6 Currently affiliated with the Johns Hopkins University School of Medicine, Baltimore, MD, USA. Received 11 March 2005; revised and accepted 19 April 2005; published online 28 July 2005

physicians educate patients about their blood pressure levels and engage patients in the effort to reach their blood pressure goals.4,7 Previous studies have evaluated the extent to which patients are aware of their hypertension,2,8–10 but little is known about the extent to which patients are aware of their blood pressure targets. Therefore, we evaluated knowledge of systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels and targets among patients hospitalized with coronary artery disease (CAD). We also sought to determine whether certain subgroups of CAD patients, defined by demographic or clinical characteristics, were particularly likely to lack knowledge of their blood pressure levels and targets.

Methods Setting and subjects

We used data from the Reinforcing Education About Cholesterol (REACH) study, a randomized trial of an

Blood pressure knowledge in CAD patients S Cheng et al 770

educational intervention designed to improve compliance with national cholesterol targets in CAD patients. The REACH study design and sampling technique have been previously described.11 Between December 1998 and January 2000, the REACH study enrolled patients aged 30–80 years who were admitted to Yale-New Haven Hospital with a new or prior diagnosis of CAD defined as: current or prior myocardial infarction (MI), current or prior coronary artery bypass graft (CABG) surgery, current or prior percutaneous coronary intervention (PCI), or a coronary artery stenosis X70% documented by cardiac catheterization. Patients were excluded if they had contraindications to taking cholesterol-lowering medication or situations or conditions that would restrict their ability to participate in an interview or benefit from an educational program.

Data collection

As part of the REACH trial, baseline demographic and clinical variables from patient medical records were abstracted, including: cardiac risk factors, history of tests and procedures (cardiac catheterization, CABG, and PCI), history of cardiovascular disease (MI, angina, cerebrovascular accident, and peripheral vascular disease (PVD)), and the first SBP, DBP measurements taken after each patient’s arrival to an inpatient unit. Upon enrollment, trained research staff interviewed all participants, a mean of 3.773.4 days after admission to assess their baseline knowledge, attitudes, and behaviours related to CAD, as well as education level and antihypertensive medication use.

Blood pressure knowledge measures

For this study, we analysed baseline REACH data including responses to patient interviews. We defined knowledge of personal SBP and/or DBP levels as a positive response to the question, ‘Do you know what your blood pressure is?’ and the ability to recall a value for SBP and/or DBP measures when subsequently asked, ‘What is it?’ We defined knowledge of SBP and/or DBP target levels as a positive response to the question, ‘Can you tell me what your blood pressure level should be?’ and the ability to name a correct value for SBP and/or DBP measures when subsequently asked, ‘What should it be?’ Blood pressure target values named by patients were compared with the thencurrent JNC VI target levels: 130 mmHg SBP and 85 mmHg DBP for patients with diabetes or renal disease; 140 mmHg SBP and 90 mmHg DBP for all other patients.5 We considered SBP and/or DBP target values named by patients to be correct if they were at or below their respective JNC VI SBP and/or DBP target. Journal of Human Hypertension

Risk assessment

Considering that CAD was for some patients a new diagnosis upon admission, we identified patients’ risk group status according to patient characteristics prior to admission and criteria outlined in the JNC VI guidelines that were current at the time of the study.5 Patients were considered to be in the highrisk group if they had any one of the following criteria for target organ damage or clinical cardiovascular disease: history of angina or MI, prior coronary revascularization (CABG or PCI), history of heart failure, history of cerebrovascular accident (CVA), or history of PVD. Patients were considered to be in the intermediate-risk group if they did not meet criteria for the high-risk group and had any one of the following major risk factors: current smoker, hypercholesterolaemia, diabetes mellitus, age 460 years, or sex (female aged X55 years, or male). Patients were considered to be in the low-risk group if they did not meet criteria for either high- or intermediate-risk groups. Statistical analysis

Dependent variables in this analysis included: ability to recall personal SBP, DBP, and both SBP and DBP levels; and ability to correctly name SBP, DBP, and both SBP and DBP targets. We used w2 tests to evaluate bivariate associations between each dependent variable and patient demographic and clinical characteristics as well as JNC VI risk group status. Based on clinical relevance and the results of bivariate analyses, relevant characteristics (female sex, age 460 years, body mass index X30 kg/m2, nonwhite ethnic group, less than any college education (o13 years), no documented prior diagnosis of hypertension, documented prior diagnosis of diabetes, and not taking antihypertensive medication) were selected and entered into a logistic regression model. To assess the independent relationship of each characteristic with the different blood pressure knowledge components, a separate model was constructed for each dependent variable. Statistical analyses were conducted with SAS statistical software, version 6.12 (SAS Institute Inc., Cary, NC, USA).

Results Of the 2657 patients screened for participation in the REACH trial, there were 1172 (44.1%) eligible patients. Of these patients, 432 (36.9%) were not enrolled due to refusal or discharge before being interviewed by research staff; these patients were similar to study patients with respect to sex, age, ethnic group, admission diagnosis, and length of stay. Baseline interviews were missing for two patients. Selected characteristics of the remaining 738 patients included in our study sample are given


in Table 1. Patient diagnoses on entry into the study included: current or prior MI (52.8%), current or prior CABG (15.3%), current or prior PCI (28.1%), and history of coronary artery stenosis X70% on cardiac catheterization (64.3%). Knowledge of personal blood pressure levels

Of the total sample, only 69.1 and 66.4% could recall a value for their SBP and DBP levels, respectively, and there was no significant difference between patients’ ability to recall SBP vs DBP values (P ¼ 0.300) (Table 2). Overall, only 66.1% of patients could recall values for both their SBP and DBP levels. Patients were less likely to recall their blood pressure levels if they were female (odds ratio (OR) 0.64, confidence interval (CI) 0.45–0.92), nonwhite (OR 0.30, CI 0.18–0.50), and without any college education (OR 0.34, CI 0.24–0.47). Having any of the JNC VI

major risk factors listed in Table 1 did not enhance patients’ knowledge of any of their personal blood pressure measures. Even patients considered high risk according to JNC VI criteria were not any more knowledgeable about their personal blood pressure levels than lower risk patients. Patients with a history of diabetes mellitus were less likely than those without diabetes to recall their SBP (62.1 vs 72.1%, P ¼ 0.070), DBP (59.8 vs 69.2%, P ¼ 0.014), and both SBP and DBP (59.8 vs 68.8%, P ¼ 0.019) blood pressure levels (data not shown in Table 2). Patients with especially poor knowledge of their personal blood pressure levels were those without either or both of their own SBP or DBP measures at goal (Table 4). Bivariate analysis also showed no association between personal blood pressure knowledge and having a documented history of hypertension or being on anti-hypertensive medication. However, in logistic regression models controlling for the effect of patient characteristics listed in Table 2, patients without a documented history of hypertension were less likely to recall their SBP (OR 0.65, CI 0.43–0.98).

Table 1 Sample characteristics n (%) Total Women Age (mean7s.d.) Body mass index kg/m2 (mean7s.d.) o25 25–30 X30

738 (100.0) 214 (29.0) 63.379.7 29.676.2 147 (20.7) 290 (40.9) 273 (38.5)

Ethnic group White Black Other

662 (90.3) 43 (5.9) 28 (3.8)

Education (mean years7s.d.) Less than any college (o13 years) At least some college (X13 years)

13.473.3 359 (50.4) 354 (49.6)

JNC VI major risk factors Smoker Hypercholesterolaemia Diabetes mellitus Age 460 years Female aged X55 years or male Any JNC VI major risk factor

140 523 224 449 705 736

(19.1) (71.4) (30.6) (60.8) (95.5) (99.7)

JNC VI target organ damage Angina or myocardial infarction Coronary revascularization Heart failure Cerebrovascular accident Peripheral vascular disease Any JNC VI target organ damage

640 251 109 61 112 661

JNC risk category A—Low B—Intermediate C—High

1 (0.1) 72 (9.8) 661 (90.1)

Documented history of hypertension On antihypertensive medication

530 (72.3) 434 (61.3)

(87.3) (34.3) (14.9) (8.3) (15.3) (90.1)

JNC ¼ Joint National Committee on Prevention, Detection, Evaluation, and treatment of high blood pressure; s.d. ¼ standard deviation.

Table 2 Knowledge of personal blood pressure levels compared between patient subgroups Recalled a value Systolic

Diastolic

Both

n (%)

n (%)

n (%)

510 (69.1)

490 (66.4)

488 (66.1)

Total Sex Women Men

126 (59.8)* 120 (56.1)* 119 (55.6)* 382 (72.9) 370 (70.6) 369 (70.4)

Age (years) o60 X60

305 (67.9) 205 (70.9)

292 (65.0) 198 (68.5)

291 (64.8) 197 (68.2)

Body mass index (kg/m2) o25 25–o30 X30

95 (64.6) 209 (72.1) 184 (67.4)

92 (62.6) 200 (69.0) 178 (65.2)

92 (62.6) 200 (69.0) 176 (64.5)


479 (72.4)* 461 (69.6) 17 (39.5) 15 (34.9) 10 (35.7) 10 (35.7)

Education Less than any college (o13 years) At least some college (X13 years) Documented history of hypertension No documented history of hypertension On antihypertensive medication Not on medication

459 (69.3)* 16 (34.9) 10 (35.7)

208 (57.9)* 196 (54.6)* 195 (54.3)* 290 (81.9)

283 (79.9)

282 (79.7)

376 (70.9)

361 (68.1)

360 (67.9)

130 (64.0)

125 (61.6)

124 (61.1)

310 (71.4)

299 (68.9)

298 (68.7)

187 (68.3)

182 (66.4)

181 (66.1)

*Po0.01. Journal of Human Hypertension


Table 3 Knowledge of blood pressure targets compared between patient subgroups Named a correct target

Total Sex Women Men

Systolic

Diastolic

Both

n (%)

n (%)

n (%)

376 (50.9)

411 (55.7)

361 (48.9)

90 (42.1)* 102 (47.7)* 82 (38.3)* 286 (54.6) 309 (59.0) 279 (53.2)

Age (years) o60 X60

216 (48.1) 160 (55.4)

246 (54.8) 165 (57.1)

206 (45.9)** 155 (53.6)

Body mass index (kg/m2) o25 25–30 X30

74 (50.3) 161 (55.5) 125 (45.8)

79 (53.7) 173 (59.7) 141 (51.7)

72 (49.0)** 156 (53.8) 118 (43.2)


348 (52.6)** 382 (57.7)* 334 (50.5)** 15 (34.9) 15 (34.9) 15 (34.9) 10 (35.7) 11 (39.3) 9 (32.1)

Education Less than any college (o13 years) At least some college (X13 years)

153 (42.6)* 164 (46.7)* 144 (40.1)* 218 (61.6)

239 (67.5)

213 (60.2)

Documented history of hypertension No documented history of hypertension

381 (53.0)

312 (58.9)* 272 (51.3)**

92 (45.3)

96 (47.3)

86 (42.4)

On anti-hypertensive medication Not on medication

231 (53.2)

258 (59.5)

223 (51.4)

140 (51.1)

148 (54.0)

133 (48.5)

Knowledge of blood pressure targets

Of the patients who demonstrated knowledge of their own SBP, DBP, and both SBP and DBP levels, a majority could correctly name their target levels (65.9% for SBP, 75.3% for DBP, and 65.4% for both values). Of the total sample, however, only 50.9 and 55.7% of all patients could correctly name their SBP and DBP targets, respectively, and the difference between patients’ ability to correctly name SBP vs DBP targets was not significant (P ¼ 0.07) (Table 3). Overall, only 48.9% of patients could correctly name both their SBP and DBP targets. Patients were less likely to name both their blood pressure targets if they were female (OR 0.69, CI 0.49–0.98), aged 460 years (OR 0.70, CI 0.51–0.97), and without any college education (OR 0.48, CI 0.35–0.65). Having any of the JNC VI major risk factors or being considered high risk according to JNC VI criteria was not associated with any knowledge of targets. However, patients without a documented history of hypertension were less likely to correctly name their SBP target and less likely to correctly name both their SBP and DBP targets overall (Table 3; OR 0.57, CI 0.39–0.84). Patients with diabetes were less likely than those without diabetes to know both their SBP and DBP targets (34.8 vs 55.0%, P ¼ 0.001). In logistic analyses, diabetes independently predicted poor knowledge of SBP targets, in particular (OR 0.48, CI 0.34–0.67). Patients with their own blood pressure measures at goal did not have enhanced knowledge of their targets except for those with their DBP at goal with regard to knowing their DBP target (Table 4).

Discussion Our study demonstrates that only a fraction of individuals hospitalized with CAD know their

*Po0.01, **Po0.05.

Table 4 Personal and target blood pressure knowledge compared with blood pressure control status Recalled a personal value

Named a correct target

Systolic

Diastolic

Both

Systolic

Diastolic

Both

n (%)

n (%)

n (%)

n (%)

n (%)

n (%)

Measured SBP At goal Not at goal

200 (43.9)** 28 (10.2)

303 (66.7) 177 (64.6)

189 (41.5)** 25 (9.1)

235 (51.5) 137 (50.0)

250 (54.8) 157 (57.3)

226 (49.6) 131 (47.8)

Measured DBP At goal Not at goal

221 (33.3)** 7 (10.8)

438 (66.2) 42 (64.6)

208 (31.3)** 6 (9.2)

334 (50.3) 38 (58.5)

363 (54.7)* 44 (67.7)

319 (48.0) 38 (58.5)

Both measured SBP and DBP At goal Not at goal

198 (44.0)** 30 (10.7)

300 (67.0) 180 (64.3)

187 (41.6)** 27 (9.6)

231 (51.3) 141 (50.4)

246 (54.7) 161 (57.5)

222 (49.3) 135 (48.2)

SBP ¼ systolic blood pressure; DBP ¼ diastolic blood pressure. *Po0.05, **Po0.01. Journal of Human Hypertension


blood pressure levels and targets. Despite numerous widespread initiatives promoting patient awareness of blood pressure levels and targets,5,12 only twothirds of patients in this study could recall both their own SBP and DBP levels, and only half could correctly name both their SBP and DBP targets as defined by JNC guidelines. While the most recent National Health and Nutrition Examination Survey (NHANES) similarly found that just over two-thirds of adults with hypertension were aware of their condition,2,5 the present study extends previous work by investigating knowledge of nationally recommended targets in a CAD patient sample. Opportunities to improve blood pressure education clearly exist among high-risk patients. In this study, a prior diagnosis of cardiovascular disease, major JNC VI risk factors, or increased JNC VI risk status did not enhance patients’ knowledge of their blood pressure levels or targets. Despite ongoing emphasis on the need to improve awareness and treatment of hypertension in high-risk patients, particularly those with diabetes,13,14 our data indicate that these patients are not benefiting from blood pressure counselling and education any more than low-risk patients. Although population studies have suggested that women are more aware of their hypertension than men,2,8–10,15 women in this study were less likely than men to have blood pressure knowledge and, in multivariate analyses, female sex independently predicted an inability to recall personal blood pressure levels and to name correct blood pressure targets. Women historically have been less aware of their cardiovascular risk than men,16,17 and women with CAD may constitute a group with less health status knowledge than women in the general population. We found that nonwhites and patients aged X60 years were also lacking in blood pressure knowledge. Population studies offer conflicting data on the significance of black ethnic group and older age with respect to hypertension awareness,2,8–10,15 but there is strong agreement regarding the importance of improving awareness and treatment in these patient groups.18–22 Although previous work has not shown an association between education level and hypertension awareness,8–10,15 we found that lack of any college education was independently associated with poor knowledge of personal blood pressure levels and targets. These data support the possibility of an interaction between education or literacy level23 on risk factor knowledge. In this study, knowledge was particularly poor in patients whose admission blood pressure measures were not at goal. Although admission blood pressure measures may have varied from patients’ average prehospital measures, our findings suggest that opportunities to enhance blood pressure knowledge are especially great among patients with uncontrolled or difficult to control hypertension. Our assessment of personal blood pressure knowledge was based on patients’ ability to recall values

for their own SBP and DBP measures. We used this conservative method for evaluating personal blood pressure knowledge since patients’ blood pressure measures before hospitalization were unavailable, and patients’ measures during admission were not considered to be representative of their out-ofhospital measurements. Previous studies have shown that the validity of self-reported hypertension awareness in the community is relatively high,24 and we would expect the validity of selfreported personal blood pressure knowledge to be similar. Since the completion of the study, the JNC 7 guidelines have been introduced with lower recommended targets.6 We compared the self-reported results with recommended targets at the time of the patient questionnaires, and do not anticipate that rates of patient knowledge would be improved by applying the current target levels to their responses. Our data were collected 4–6 years ago, but since no new major educational interventions regarding blood pressure have occurred in the interim, our results likely reflect the current situation regarding blood pressure knowledge. Our findings were limited to patients admitted to the hospital and their acute condition, or treatments for their condition, could have compromised their ability to demonstrate health knowledge. This sampling technique may have contributed to the low rates of blood pressure knowledge we report, although studies to date have found similarly low rates of hypertension awareness among nonhospitalized patients.5,25 Such comparable results also suggest that our findings, while limited to a single centre, are likely to be supported by further population-based investigations of blood pressure knowledge. However, the generalizability of our results is limited by the fact that nonwhites comprised less than 10% and women only 30% of our study sample. Studies in more diverse patient samples are needed to further elucidate blood pressure knowledge in these groups. Our study sample was also subject to a selection bias imposed by exclusion as well as inclusion criteria of the REACH trial. In particular, our sample did not include patients who were unable to provide informed consent or be interviewed, and patients deemed unable to participate in or benefit from an educational program. However, including such patients would likely have resulted in even lower knowledge rates, further supporting the overall findings of this study. Despite ongoing efforts to educate patients about the importance of lowering high blood pressure, this study demonstrates that a significant proportion of CAD patients lack knowledge of their blood pressure levels and targets. Blood pressure knowledge is especially poor among women, nonwhites, and individuals without any college education. More targeted blood pressure educational interventions may be needed to reach these patient subgroups and improve upon overall efforts to decrease the prevalence of hypertension (Table 5). Journal of Human Hypertension


Table 5 Existing knowledge and new findings What is known on this topic: Only two thirds of adults with hypertension in the general population are aware of their condition

K

What this study adds: Specific knowledge of blood pressure targets as well as personal blood pressure levels is poor among high-risk individuals K Individuals with increased cardiovascular risk are no more likely than their counterparts to have blood pressure knowledge K Only two-thirds of adults with coronary artery disease are able to recall their own systolic and diastolic blood pressure levels K Only half of adults with coronary artery disease are able to name their systolic and diastolic blood pressure targets K

Acknowledgements This study was supported by a grant from Pfizer. Dr Lichtman is a Goddess Fund Career Development Scholar. There are no relationships that could be perceived as real or apparent conflict(s) of interest with regard to the subject matter of this manuscript.

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