Journal of Human Hypertension (2014) 28, 500–503 & 2014 Macmillan Publishers Limited All rights reserved 0950-9240/14 www.nature.com/jhh
ORIGINAL ARTICLE
Knowledge of blood pressure in a UK general public population J Slark1,2, MS Khan1,2, P Bentley1,2 and P Sharma1,2 Little is known about the general public’s understanding of the role of blood pressure (BP) in contributing to heart disease and stroke. This study aimed to gain a wider understanding of the knowledge and awareness of BP in a selected London population. As part of a stroke awareness campaign, members of the public were offered BP testing and were asked about their knowledge and awareness of BP. Descriptive statistics were employed to explore knowledge and awareness of BP. w2-test was run to explore the difference between knowledge and awareness of BP, and whether there was a difference in BP readings in normotensive and hypertensive participants. A total of 1019 participants (males 295; mean age 54 years, range 16–92) were recruited with a mean BP of 130/77 mm Hg. Over half (52%) of the total population was unable to correctly estimate an acceptable range of BP, and of that group 28% had a systolic BP (SBP) 4140 mm Hg. Of the 31% self-reporting hypertension and on medication, over a quarter (27%) did not know the range for acceptable BP. A third were poorly controlled with a SBP 4140 mm Hg. Mean SBP in the hypertensive participants who correctly estimated ‘acceptable BP’ was 3 mm Hg lower (147 mm Hg) than those who guessed incorrectly (150 mm Hg) (Po0.04). There remains a lack of understanding of BP in the general public population with individuals having little knowledge of an acceptable BP range. Hypertensive patients demonstrate a particularly poor understanding of BP. This study suggests that good knowledge of BP influences BP control in a hypertensive population and has important public health implications. Journal of Human Hypertension (2014) 28, 500–503; doi:10.1038/jhh.2013.136; published online 16 January 2014 Keywords: knowledge of BP; risk awareness; blood pressure; BP control
INTRODUCTION Nearly half of all strokes in patients who are on treatment for hypertension could be attributed to poorly controlled blood pressure (BP).1 Understanding why BP is so poorly controlled in the hypertensive population is an important question. Patients who recognize their increased risk for stroke are more likely to engage in stroke prevention practices than those who do not.2 However, both the general public and hypertensive patients alike do not consider hypertension as a serious health problem with only one-third recognizing that hypertension could be asymptomatic.3 Previous work in this field has demonstrated that while hypertensive patients have a general understanding of hypertension, they are less knowledgeable about specific factors related to their condition and in particular their own level of BP control.4 Patients who are aware that elevated BP levels can lead to reductions in life expectancy have been reported to have a higher compliance level with medication use and follow-up visits than patients without this awareness.5 The West London borough (population 170 000) has a population that has a highly diverse cultural and ethnic mix. Poor BP control remains a common problem that contributes to significant morbidity and mortality particularly among ethnic minority groups and lower socioeconomic communities.6 In all, 18% of adults aged between 16 and 74 years of age have no formal qualifications in the borough. The influence of educational level, poorer outcomes and levels of care delivery for ethnic minority groups are a consideration for this local population; therefore, a random study would include a large number of low education level and ethnic minority groups, 1
although this was not specifically studied as part of this project. The literature informs us that there is little knowledge or understanding of BP and its role as a major risk factor for stroke and heart disease in the general public.3,7,8 However, this study sought to gain an understanding of a general population’s knowledge of BP, including awareness of their own, in the diverse metropolitan city of London. We also sought to determine whether knowledge of an acceptable range for BP influenced BP control in both hypertensive and normotensive members of the general public. Also in light of recent changes to cardiovascular risk factor management, and the introduction of the Quality Outcomes Framework (QOF),9 this study sought to identify whether there have been changes to the level of knowledge and awareness in the hypertensive population regarding acceptable BP levels. MATERIALS AND METHODS As part of an awareness campaign about stroke, members of the public were offered BP testing and, following a verbal consent, were asked validated questions to identify their perception and understanding of BP. The questions were validated through a smaller pilot study on 12 healthy and hypertensive volunteers. The questions included asking the participant to give an estimate of a ‘normal’ BP and an estimate of their own BP reading. The use of the wording was changed to ‘estimate’ rather than ‘guess’ and from ‘normal’ to ‘acceptable’ following responses from the pilot study. BP readings were performed by a trained health professional according to British Hypertension Society (BHS) guidelines.10 All members of the public were approached to participate in BP testing, from local venues such as Town Hall, shopping centres, coffee shops, foyers and a local exhibition hall during a careers exhibition.
Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand and 2Imperial College Cerebrovascular Research Unit (ICCRU), Imperial College London, London, UK. Correspondence: Dr J Slark, Faculty of Medical and Health Sciences, University of Auckland, Building 505, Level 2, 85, Park Road, Grafton, Auckland 1142, New Zealand. E-mail: [email protected] Received 5 June 2013; revised 19 November 2013; accepted 29 November 2013; published online 16 January 2014
Knowledge of BP in the general population J Slark et al
501 The British Hypertension Society classification (2004)10 of an ‘acceptable’ BP equates to that of the European Society of Hypertension (2013),11 which states that the systolic BP (SBP) should be o140 mm Hg and the diastolic BP should be o90 mm Hg for almost all patients, in contrast to the 2007 guidelines that recommended a 140/90 mm Hg target for moderate-tolow-risk and 130/80 mm Hg for high-risk patients.11 The BHS10 classification of optimal, normal, high-normal, mild, moderate and severe hypertension are shown in Table 1.10 BP was measured using sphygmomanometry and validated electronic BP devices12 (Omron 637IT, Omron Matsusaka Co. Ltd., Kyoto, Japan) using the BHS guidelines for BP measurement (2004).10 Demographic details were documented and individuals were asked about their knowledge of ‘acceptable’ BP range and to give an example or estimate a figure. Acceptable range of BP was defined as o140/90 mm Hg and participants with a BP reading in excess of this value on three consecutive recordings were advised to see their general practitioner for further advice and investigation and were provided with specific information regarding high BP.
Aims and objectives To determine the level of knowledge of acceptable BP levels in
normotensive and hypertensive members of the general public population.
Knowledge of normal BP values is associated with lower BP readings in hypertensives 152
Measured SBP
influences BP readings in normotensive and hypertensive members of the general public population.
Hypothesis Hypertensives have a better knowledge of an acceptable BP compared
with normotensive members of the general public. Poor knowledge of ‘acceptable’ BP in hypertensive participants has
negative impact on BP control.
Power calculation The power calculation was defined using results from a similar study that defined acceptable BP as o140/90 mm Hg and identified that normotensive participants had a better awareness of normal SBP and diastolic BP values than subjects with hypertension. The mean values of BP stated as normal by hypertensives were significantly higher than those reported by normotensives. The reported difference in knowledge was 47%,13 with 95% confidence and with a 3.15-bond on error of estimation. A sample of 965 patients was required to gain an understanding of the local population’s perception of BP and allowing for a 5% refusal rate our final sample size was 1019.
Data were analysed using SPSS version.17 software (Chicago, IL, USA). Descriptive statistics were employed to explore the knowledge and awareness of BP. Independent t-test was used to identify significant differences in age and BP control between healthy and hypertensive populations. w2-test was run to explore the differences between knowledge and awareness of BP and influences BP readings in normotensive and hypertensive participants, a P-value o0.05 was considered significant. Logistic regression was run to identify the independent association of knowledge with hypertension status.
T-test p = 0.04
148
145
Know Don’t Know normal normal BP values BP values
Figure 1. Comparison between hypertensive and normotensive BP readings.
Table 1.
and normotensive members of the general public population. To observe whether differences in knowledge and awareness of BP
Analysis
150
140
To identify the awareness of personal BP readings in the hypertensive
RESULTS There were 1019 (males 29%) participants (mean age 54 years; s.d. 16–92) (Table 2). Mean BP for the total population was 130/ 77 mm Hg. The mean (s.d.) age for the hypertensive population (n ¼ 313) was 65 (12) years and for the normotensive population 50 (16.7) years (P ¼ o0.001). Only 31% of this population had an optimal BP (o120/80 mm Hg) recording on the day and 33% had mild-severe hypertension10 on BP recordings (4140/90 mm Hg). The mean SBP for the hypertensive population was 139.5 mm Hg compared with 125.4 mm Hg in the normotensive group (Po0.001) (Table 4). In total, 194 people (19%) who participated in the campaign had consistently high readings on the day according to BHS guidelines10 and were advised to see their general practitioner and were provided with written information of their BP recording to discuss with them. A total of 313
British Hypertension Society guidelines for hypertension management 2004
BP category
Optimal Normal High normal Mild hypertension (grade 1) Moderate hypertension (grade 2) Severe hypertension (grade 3)
Grades of hypertension Systolic BP (mm Hg)
Diastolic BP (mm Hg)
o120 X120 þ o130 X130 þ o139 140–159 160–179 4180
o80 X80 þ o85 X85 þ o89 90–99 100–109 4110
Lifestyle
Drug therapy
— Yes Yes Yes Yes
— Consider* Consider þ Yes Yes
Abbreviation: BP, blood pressure. *Drug therapy may be indicated for people with established cardiovascular disease, chronic renal disease or diabetes with complications at BP levels 4130/80 mmHg. þ Drug therapy is recommended for people with established cardiovascular disease and diabetes or evidence of target organ damage or a 10-year CVD risk of 420%.
& 2014 Macmillan Publishers Limited
Journal of Human Hypertension (2014) 500 – 503
Knowledge of BP in the general population J Slark et al
502 Table 2.
Table 4.
Population characteristics
Population characteristics Age Range Female Self-reported hypertension Self-reported taking medications for BP Did not know acceptable BP or guessed incorrectly Did not know own BP or guessed incorrectly Total clinically hypertensive
(n ¼ 1019)
%
54 years 16–92 724 313 299 259
71 31 29 52
592 334
58 33
Hypertensive compared with normotensive results
Variables Age, years Mean (s.d.)
Hypertensive, n (%)
Normotensive, n (%)
65.3 (12)
49.6 (17)
96 (30.7) 217 (69.3)) 139.5 (17.4)
199 (28.2) 507 (71.8) 125.4 (16.9)
o0.001 o0.001
o0.001 0.420
Abbreviation: BP, blood pressure.
Gender Male Female Mean (s.d.), SBP, mm Hg Mean (s.d.), DBP, mm Hg
80.9 (12.6)
74.9 (11.4)
Table 3.
Knowledge of acceptable BP Yes 168 (34.3) No 145 (27.4)
322 (65.7) 384 (72.6)
Awareness of personal BP Yes 160 (37.5) No 153 (25.8)
267 (62.5) 439 (74.2)
Knowledge of acceptable BP and awareness of own BP
Questions
No idea/guessed incorrectly (n ¼ 1019)
%
529
52
592
58
194
19
What do you think is an ‘acceptable’ BP? What do you think is your own BP reading? GP referrals made
Abbreviations: BP, blood pressure; GP, general practitioner.
participants self-reported hypertension, of whom 299 reported taking medications for BP. In all, 52% (n ¼ 529) of the total participants were unable to provide an estimated range for ‘acceptable’ BP (Table 3). Among participants who had knowledge of acceptable BP, only 34% were hypertensive (P-value 0.017). Similarly, among participants who were aware of personal BP only 38% were hypertensive (P-value o0.001). Hypertensive participants’ had 51% (OR (confidence interval 95%) 0.49 (0.37, 0.68)) lower knowledge of acceptable BP compared with the normotensive population adjusted for age and gender. Independent t-test calculated mean BP in the hypertensive participants who guessed acceptable BP correctly as SBP 147 mm Hg and those who guessed incorrectly as SBP 150 mm Hg, which had a significant P-value of 0.047 (confidence interval 95% s.d. 9.3–12.6; Figure 1). There were 334 (33%) people with a SBP of 4155 mm Hg, which may put them at an increased risk of stroke.14 DISCUSSION Our results demonstrate a poor understanding of BP in the general population in London. Known hypertensive participants have little knowledge of their own BP and are unable to estimate BP within acceptable levels. Knowledge about BP was associated with better control of it at the individual level. Hypertension is the highest modifiable risk factor for cardiovascular diseases15 and the prevalence of hypertension and diabetes is rising owing to global increases in obesity; and in conjunction with the ageing population,15 the risk to patients is very real. The diagnosis and treatment of hypertension is therefore, of paramount importance to the prevention of cardiovascular diseases such as heart disease and stroke. However, non-adherence, poor management and a lack of routine monitoring are all reasons mentioned in the literature for poor BP control in the general population.2–4,7. Patient’s understanding of acceptable BP may enable them to participate in the management of their care and be more likely to initiate behavioural changes to reduce their BP.5 It was disappointing that only one-third (34%) of the hypertensive group was able to estimate an ‘acceptable’ BP correctly Journal of Human Hypertension (2014) 500 – 503
P-value
0.017
o0.001
Abbreviations: BP, blood pressure; DBP, diastolic BP; GP, general practitioner; SBP, systolic BP.
compared with 66% in the normotensive group. It is possible that hypertensives are more familiar with higher BP readings. Selected BP readings may have been higher due to the participant’s recent activities but this is likely to be the same if recorded in a busy clinical environment. As health professionals undertook BP measurements, the results could also have been influenced by a ‘white coat’ reaction. The study identified that hypertensives were 51% less likely to know an acceptable BP range than normotensive patients. The study did not correct for other factors that may have affected this association such as level of patient education, time since hypertensive diagnosis, contact with the general practitioner and other life style factors that suggest an interest in health. These factors may influence whether people more interested in their own health are more likely to engage with healthy behaviours—thus, have a normal BP and know what an acceptable BP range is. However, when asked about their own BP, only 38% of the hypertensive group compared with 62% of normotensives were able to estimate it correctly (Table 4). This is despite a generous 10 mm Hg margin either side of the estimate, which clinically is a significant number in terms of BP control.16 From the readings, it appears one-third (31%) of the hypertensive population’s BP was uncontrolled with a SBP X140 mm Hg. The lack of public and patient awareness of the importance of hypertension control for general good health and stroke prevention is well documented.2–4 The data from this project support these findings and concur with Egan et al.17 who found that nearly half (46%) of their American hypertensive population did not know their own BP either. Despite populations from different countries, the two studies suggest the link between knowledge and control of BP is substantial and more importantly in older hypertensive patients who seem to have little knowledge of BP despite having a diagnosis of the condition. Despite previous studies highlighting the lack of knowledge about BP in hypertensive patients,17 10 years on this problem remains. This study is unique as it provides local health services with valuable information about the knowledge and perception of BP in its local population. Therefore, future awareness and information campaigns can be focused towards known hypertensive’s knowledge and they have been given access to health professionals regarding their BP. This study has identified that this population group have little insight into their condition and understanding of what their BP should acceptably be. & 2014 Macmillan Publishers Limited
Knowledge of BP in the general population J Slark et al
503 A number of limitations need to be noted in this study: as primarily, ethnicity was not recorded, but with the majority of subjects of European descent, our results should be interpreted with caution in different ancestral groups. Our population was disproportionately largely comprised of women and this may have occurred because of the location of venues chosen. Those who are knowledgeable about BP may simply be knowledgeable about all health issues and live a healthier lifestyle compared with the hypertensive cohort in this study. It is important to note that the elevated BP recordings on the day may be due to the environmental aspects of the study location and the ambulant subject population being assessed. Subjects were approached in a consecutive order to eliminate bias. Our study shows the importance of continued BP education. Knowledge is important because it is associated with better BP control and education strategies to improve patient knowledge should be encouraged in clinical practices.
What is known about the topic Hypertension is the highest modifiable risk factor for stroke. Awareness of blood pressure (BP) as a risk factor for stroke is poor in the general population. Hypertensives in the general population do not realise that BP is asymptomatic and do not consider it as a major health problem. It is suggested that those with awareness and knowledge of BP are more likely to participate in lifestyle behaviours to control their BP than those who are less knowledgeable. What this study adds This study adds knowledge of the awareness and understanding of BP in a London population to inform health information programmes for the general public. This study highlights important information regarding knowledge of acceptable BP in hypertensive members of the public and suggests knowledge of BP influences BP control in this population.
CONFLICT OF INTEREST JS and MSK have no conflict of interest. PS and PB hold Department of Health Senior Fellowships.
& 2014 Macmillan Publishers Limited
REFERENCES 1 Li C, Engstroem G, Hedblad B, Berglund G, Janzon L. Blood pressure control and risk of stroke: a population-based prospective cohort study. Stroke 2005; 36: 725–730. 2 Samsa G, Cohen S, Goldstein L, Bonito A, Duncan P, Enarson C et al. Knowledge of risk among patients at increased risk of stroke. Stroke 1997; 28: 916–921. 3 Volpe M, Dedhiya SD. Physicians, patients and public knowledge and perception regarding hypertension and stroke: a review of survey studies. Curr Med Res Opin 2006; 22(7): 1319–1330. 4 Oliveria S, Chen R, McCarthy B, Davis C, Hill M. Hypertension knowledge, awareness and attitudes in a hypertensive population. J Gen Intern Med 2005; 20: 219–225. 5 Balazovjech I, Hnilica Jr. P. Compliance with antihypertensive treatment in consultation rooms for hypertensive patients. J Hum Hypertens 1993; 7: 581–583. 6 Bosworth HB, Dudley T, Olson MK, Volis CI, Powers B, Goldstein MK et al. Racial differences in blood pressure control: potential explanatory factors. Am J Med 2006; 119(70): E9–15. 7 Samal D, Greisenegger S, Auff E, Lang W, Lalouschek W. The relation between knowledge about hypertension and education in hospitalized patients with stroke in Vienna. Stroke 2007; 38: 1304–1308. 8 Cellentano A, Palmeiri V, Arezzi E, Sabatella M, Guillaro B, Brancati C et al. Cardiovascular secondary prevention: patient’s knowledge of cardiovascular risk factors and their attitude to reduce the risk burden, and the practice of family doctors. The ‘help your heart stay young’ study. Ital Heart J 2004; 5: 767–773. 9 Campell SM, Reeves D, Kontopantelis E, Sibbald B, Roland M. Effects of pay for performance on the quality of primary care in England. N Engl J Med 2009; 361(4): 368–378. 10 Williams B, Poulter MR, Brown MJ, Davis M, McInnes GT, Potter JF et al. British Hypertension Society guidelines for hypertension management 2004 (BHS-IV): summary. BMJ 2004; 328(7440): 634–640. 11 Zanchetti A. European Society of Hypertension-European Society of Cardiology Guidelines Committee. European Society of Hypertension-European Society of Cardiology guidelines for the management of arterial hypertension. J Hypertens 2003; 21: 1011–1053. 12 Altunkan S, Oztas K, Altunkan E. Validation of the OMRON 637IT wrist BP measuring device with a position sensor according to the international protocol in adults and obese adults. Blood Press Monit 2006; 11(2): 79–85. 13 Wizner B, Gryglewska B, Gasowski J, Kocemba J, Grodzick T. Normal BP values as perceived by normotensive and hypertensive subjects. J Hum Hypertens 2003; 17: 87–91. 14 McMahon S, Rodgers A. Blood pressure, antihypertensive treatment and stroke risk. J Hypertens 1994; 12(SUPP 10): S5–S14. 15 World Health Organization. Cardiovascular diseases. Fact sheet No. 317. http:// www.who.int/mediacentre/factsheets/fs317/en/. Accessed on 19 April 2013. 16 Mancia G. Blood pressures reduction and cardiovascular disease outcomes: past, present and future. Am J Cardiol 2007; 100(SUPP): 3J–9J. 17 Egan BM, Lackland DT, Cutler NE. Awareness, knowledge and attitudes of older Americans about high BP. Arch Intern Med 2003; 163: 681–687.
Journal of Human Hypertension (2014) 500 – 503
ORIGINAL ARTICLE
Knowledge of blood pressure in a UK general public population J Slark1,2, MS Khan1,2, P Bentley1,2 and P Sharma1,2 Little is known about the general public’s understanding of the role of blood pressure (BP) in contributing to heart disease and stroke. This study aimed to gain a wider understanding of the knowledge and awareness of BP in a selected London population. As part of a stroke awareness campaign, members of the public were offered BP testing and were asked about their knowledge and awareness of BP. Descriptive statistics were employed to explore knowledge and awareness of BP. w2-test was run to explore the difference between knowledge and awareness of BP, and whether there was a difference in BP readings in normotensive and hypertensive participants. A total of 1019 participants (males 295; mean age 54 years, range 16–92) were recruited with a mean BP of 130/77 mm Hg. Over half (52%) of the total population was unable to correctly estimate an acceptable range of BP, and of that group 28% had a systolic BP (SBP) 4140 mm Hg. Of the 31% self-reporting hypertension and on medication, over a quarter (27%) did not know the range for acceptable BP. A third were poorly controlled with a SBP 4140 mm Hg. Mean SBP in the hypertensive participants who correctly estimated ‘acceptable BP’ was 3 mm Hg lower (147 mm Hg) than those who guessed incorrectly (150 mm Hg) (Po0.04). There remains a lack of understanding of BP in the general public population with individuals having little knowledge of an acceptable BP range. Hypertensive patients demonstrate a particularly poor understanding of BP. This study suggests that good knowledge of BP influences BP control in a hypertensive population and has important public health implications. Journal of Human Hypertension (2014) 28, 500–503; doi:10.1038/jhh.2013.136; published online 16 January 2014 Keywords: knowledge of BP; risk awareness; blood pressure; BP control
INTRODUCTION Nearly half of all strokes in patients who are on treatment for hypertension could be attributed to poorly controlled blood pressure (BP).1 Understanding why BP is so poorly controlled in the hypertensive population is an important question. Patients who recognize their increased risk for stroke are more likely to engage in stroke prevention practices than those who do not.2 However, both the general public and hypertensive patients alike do not consider hypertension as a serious health problem with only one-third recognizing that hypertension could be asymptomatic.3 Previous work in this field has demonstrated that while hypertensive patients have a general understanding of hypertension, they are less knowledgeable about specific factors related to their condition and in particular their own level of BP control.4 Patients who are aware that elevated BP levels can lead to reductions in life expectancy have been reported to have a higher compliance level with medication use and follow-up visits than patients without this awareness.5 The West London borough (population 170 000) has a population that has a highly diverse cultural and ethnic mix. Poor BP control remains a common problem that contributes to significant morbidity and mortality particularly among ethnic minority groups and lower socioeconomic communities.6 In all, 18% of adults aged between 16 and 74 years of age have no formal qualifications in the borough. The influence of educational level, poorer outcomes and levels of care delivery for ethnic minority groups are a consideration for this local population; therefore, a random study would include a large number of low education level and ethnic minority groups, 1
although this was not specifically studied as part of this project. The literature informs us that there is little knowledge or understanding of BP and its role as a major risk factor for stroke and heart disease in the general public.3,7,8 However, this study sought to gain an understanding of a general population’s knowledge of BP, including awareness of their own, in the diverse metropolitan city of London. We also sought to determine whether knowledge of an acceptable range for BP influenced BP control in both hypertensive and normotensive members of the general public. Also in light of recent changes to cardiovascular risk factor management, and the introduction of the Quality Outcomes Framework (QOF),9 this study sought to identify whether there have been changes to the level of knowledge and awareness in the hypertensive population regarding acceptable BP levels. MATERIALS AND METHODS As part of an awareness campaign about stroke, members of the public were offered BP testing and, following a verbal consent, were asked validated questions to identify their perception and understanding of BP. The questions were validated through a smaller pilot study on 12 healthy and hypertensive volunteers. The questions included asking the participant to give an estimate of a ‘normal’ BP and an estimate of their own BP reading. The use of the wording was changed to ‘estimate’ rather than ‘guess’ and from ‘normal’ to ‘acceptable’ following responses from the pilot study. BP readings were performed by a trained health professional according to British Hypertension Society (BHS) guidelines.10 All members of the public were approached to participate in BP testing, from local venues such as Town Hall, shopping centres, coffee shops, foyers and a local exhibition hall during a careers exhibition.
Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand and 2Imperial College Cerebrovascular Research Unit (ICCRU), Imperial College London, London, UK. Correspondence: Dr J Slark, Faculty of Medical and Health Sciences, University of Auckland, Building 505, Level 2, 85, Park Road, Grafton, Auckland 1142, New Zealand. E-mail: [email protected] Received 5 June 2013; revised 19 November 2013; accepted 29 November 2013; published online 16 January 2014
Knowledge of BP in the general population J Slark et al
501 The British Hypertension Society classification (2004)10 of an ‘acceptable’ BP equates to that of the European Society of Hypertension (2013),11 which states that the systolic BP (SBP) should be o140 mm Hg and the diastolic BP should be o90 mm Hg for almost all patients, in contrast to the 2007 guidelines that recommended a 140/90 mm Hg target for moderate-tolow-risk and 130/80 mm Hg for high-risk patients.11 The BHS10 classification of optimal, normal, high-normal, mild, moderate and severe hypertension are shown in Table 1.10 BP was measured using sphygmomanometry and validated electronic BP devices12 (Omron 637IT, Omron Matsusaka Co. Ltd., Kyoto, Japan) using the BHS guidelines for BP measurement (2004).10 Demographic details were documented and individuals were asked about their knowledge of ‘acceptable’ BP range and to give an example or estimate a figure. Acceptable range of BP was defined as o140/90 mm Hg and participants with a BP reading in excess of this value on three consecutive recordings were advised to see their general practitioner for further advice and investigation and were provided with specific information regarding high BP.
Aims and objectives To determine the level of knowledge of acceptable BP levels in
normotensive and hypertensive members of the general public population.
Knowledge of normal BP values is associated with lower BP readings in hypertensives 152
Measured SBP
influences BP readings in normotensive and hypertensive members of the general public population.
Hypothesis Hypertensives have a better knowledge of an acceptable BP compared
with normotensive members of the general public. Poor knowledge of ‘acceptable’ BP in hypertensive participants has
negative impact on BP control.
Power calculation The power calculation was defined using results from a similar study that defined acceptable BP as o140/90 mm Hg and identified that normotensive participants had a better awareness of normal SBP and diastolic BP values than subjects with hypertension. The mean values of BP stated as normal by hypertensives were significantly higher than those reported by normotensives. The reported difference in knowledge was 47%,13 with 95% confidence and with a 3.15-bond on error of estimation. A sample of 965 patients was required to gain an understanding of the local population’s perception of BP and allowing for a 5% refusal rate our final sample size was 1019.
Data were analysed using SPSS version.17 software (Chicago, IL, USA). Descriptive statistics were employed to explore the knowledge and awareness of BP. Independent t-test was used to identify significant differences in age and BP control between healthy and hypertensive populations. w2-test was run to explore the differences between knowledge and awareness of BP and influences BP readings in normotensive and hypertensive participants, a P-value o0.05 was considered significant. Logistic regression was run to identify the independent association of knowledge with hypertension status.
T-test p = 0.04
148
145
Know Don’t Know normal normal BP values BP values
Figure 1. Comparison between hypertensive and normotensive BP readings.
Table 1.
and normotensive members of the general public population. To observe whether differences in knowledge and awareness of BP
Analysis
150
140
To identify the awareness of personal BP readings in the hypertensive
RESULTS There were 1019 (males 29%) participants (mean age 54 years; s.d. 16–92) (Table 2). Mean BP for the total population was 130/ 77 mm Hg. The mean (s.d.) age for the hypertensive population (n ¼ 313) was 65 (12) years and for the normotensive population 50 (16.7) years (P ¼ o0.001). Only 31% of this population had an optimal BP (o120/80 mm Hg) recording on the day and 33% had mild-severe hypertension10 on BP recordings (4140/90 mm Hg). The mean SBP for the hypertensive population was 139.5 mm Hg compared with 125.4 mm Hg in the normotensive group (Po0.001) (Table 4). In total, 194 people (19%) who participated in the campaign had consistently high readings on the day according to BHS guidelines10 and were advised to see their general practitioner and were provided with written information of their BP recording to discuss with them. A total of 313
British Hypertension Society guidelines for hypertension management 2004
BP category
Optimal Normal High normal Mild hypertension (grade 1) Moderate hypertension (grade 2) Severe hypertension (grade 3)
Grades of hypertension Systolic BP (mm Hg)
Diastolic BP (mm Hg)
o120 X120 þ o130 X130 þ o139 140–159 160–179 4180
o80 X80 þ o85 X85 þ o89 90–99 100–109 4110
Lifestyle
Drug therapy
— Yes Yes Yes Yes
— Consider* Consider þ Yes Yes
Abbreviation: BP, blood pressure. *Drug therapy may be indicated for people with established cardiovascular disease, chronic renal disease or diabetes with complications at BP levels 4130/80 mmHg. þ Drug therapy is recommended for people with established cardiovascular disease and diabetes or evidence of target organ damage or a 10-year CVD risk of 420%.
& 2014 Macmillan Publishers Limited
Journal of Human Hypertension (2014) 500 – 503
Knowledge of BP in the general population J Slark et al
502 Table 2.
Table 4.
Population characteristics
Population characteristics Age Range Female Self-reported hypertension Self-reported taking medications for BP Did not know acceptable BP or guessed incorrectly Did not know own BP or guessed incorrectly Total clinically hypertensive
(n ¼ 1019)
%
54 years 16–92 724 313 299 259
71 31 29 52
592 334
58 33
Hypertensive compared with normotensive results
Variables Age, years Mean (s.d.)
Hypertensive, n (%)
Normotensive, n (%)
65.3 (12)
49.6 (17)
96 (30.7) 217 (69.3)) 139.5 (17.4)
199 (28.2) 507 (71.8) 125.4 (16.9)
o0.001 o0.001
o0.001 0.420
Abbreviation: BP, blood pressure.
Gender Male Female Mean (s.d.), SBP, mm Hg Mean (s.d.), DBP, mm Hg
80.9 (12.6)
74.9 (11.4)
Table 3.
Knowledge of acceptable BP Yes 168 (34.3) No 145 (27.4)
322 (65.7) 384 (72.6)
Awareness of personal BP Yes 160 (37.5) No 153 (25.8)
267 (62.5) 439 (74.2)
Knowledge of acceptable BP and awareness of own BP
Questions
No idea/guessed incorrectly (n ¼ 1019)
%
529
52
592
58
194
19
What do you think is an ‘acceptable’ BP? What do you think is your own BP reading? GP referrals made
Abbreviations: BP, blood pressure; GP, general practitioner.
participants self-reported hypertension, of whom 299 reported taking medications for BP. In all, 52% (n ¼ 529) of the total participants were unable to provide an estimated range for ‘acceptable’ BP (Table 3). Among participants who had knowledge of acceptable BP, only 34% were hypertensive (P-value 0.017). Similarly, among participants who were aware of personal BP only 38% were hypertensive (P-value o0.001). Hypertensive participants’ had 51% (OR (confidence interval 95%) 0.49 (0.37, 0.68)) lower knowledge of acceptable BP compared with the normotensive population adjusted for age and gender. Independent t-test calculated mean BP in the hypertensive participants who guessed acceptable BP correctly as SBP 147 mm Hg and those who guessed incorrectly as SBP 150 mm Hg, which had a significant P-value of 0.047 (confidence interval 95% s.d. 9.3–12.6; Figure 1). There were 334 (33%) people with a SBP of 4155 mm Hg, which may put them at an increased risk of stroke.14 DISCUSSION Our results demonstrate a poor understanding of BP in the general population in London. Known hypertensive participants have little knowledge of their own BP and are unable to estimate BP within acceptable levels. Knowledge about BP was associated with better control of it at the individual level. Hypertension is the highest modifiable risk factor for cardiovascular diseases15 and the prevalence of hypertension and diabetes is rising owing to global increases in obesity; and in conjunction with the ageing population,15 the risk to patients is very real. The diagnosis and treatment of hypertension is therefore, of paramount importance to the prevention of cardiovascular diseases such as heart disease and stroke. However, non-adherence, poor management and a lack of routine monitoring are all reasons mentioned in the literature for poor BP control in the general population.2–4,7. Patient’s understanding of acceptable BP may enable them to participate in the management of their care and be more likely to initiate behavioural changes to reduce their BP.5 It was disappointing that only one-third (34%) of the hypertensive group was able to estimate an ‘acceptable’ BP correctly Journal of Human Hypertension (2014) 500 – 503
P-value
0.017
o0.001
Abbreviations: BP, blood pressure; DBP, diastolic BP; GP, general practitioner; SBP, systolic BP.
compared with 66% in the normotensive group. It is possible that hypertensives are more familiar with higher BP readings. Selected BP readings may have been higher due to the participant’s recent activities but this is likely to be the same if recorded in a busy clinical environment. As health professionals undertook BP measurements, the results could also have been influenced by a ‘white coat’ reaction. The study identified that hypertensives were 51% less likely to know an acceptable BP range than normotensive patients. The study did not correct for other factors that may have affected this association such as level of patient education, time since hypertensive diagnosis, contact with the general practitioner and other life style factors that suggest an interest in health. These factors may influence whether people more interested in their own health are more likely to engage with healthy behaviours—thus, have a normal BP and know what an acceptable BP range is. However, when asked about their own BP, only 38% of the hypertensive group compared with 62% of normotensives were able to estimate it correctly (Table 4). This is despite a generous 10 mm Hg margin either side of the estimate, which clinically is a significant number in terms of BP control.16 From the readings, it appears one-third (31%) of the hypertensive population’s BP was uncontrolled with a SBP X140 mm Hg. The lack of public and patient awareness of the importance of hypertension control for general good health and stroke prevention is well documented.2–4 The data from this project support these findings and concur with Egan et al.17 who found that nearly half (46%) of their American hypertensive population did not know their own BP either. Despite populations from different countries, the two studies suggest the link between knowledge and control of BP is substantial and more importantly in older hypertensive patients who seem to have little knowledge of BP despite having a diagnosis of the condition. Despite previous studies highlighting the lack of knowledge about BP in hypertensive patients,17 10 years on this problem remains. This study is unique as it provides local health services with valuable information about the knowledge and perception of BP in its local population. Therefore, future awareness and information campaigns can be focused towards known hypertensive’s knowledge and they have been given access to health professionals regarding their BP. This study has identified that this population group have little insight into their condition and understanding of what their BP should acceptably be. & 2014 Macmillan Publishers Limited
Knowledge of BP in the general population J Slark et al
503 A number of limitations need to be noted in this study: as primarily, ethnicity was not recorded, but with the majority of subjects of European descent, our results should be interpreted with caution in different ancestral groups. Our population was disproportionately largely comprised of women and this may have occurred because of the location of venues chosen. Those who are knowledgeable about BP may simply be knowledgeable about all health issues and live a healthier lifestyle compared with the hypertensive cohort in this study. It is important to note that the elevated BP recordings on the day may be due to the environmental aspects of the study location and the ambulant subject population being assessed. Subjects were approached in a consecutive order to eliminate bias. Our study shows the importance of continued BP education. Knowledge is important because it is associated with better BP control and education strategies to improve patient knowledge should be encouraged in clinical practices.
What is known about the topic Hypertension is the highest modifiable risk factor for stroke. Awareness of blood pressure (BP) as a risk factor for stroke is poor in the general population. Hypertensives in the general population do not realise that BP is asymptomatic and do not consider it as a major health problem. It is suggested that those with awareness and knowledge of BP are more likely to participate in lifestyle behaviours to control their BP than those who are less knowledgeable. What this study adds This study adds knowledge of the awareness and understanding of BP in a London population to inform health information programmes for the general public. This study highlights important information regarding knowledge of acceptable BP in hypertensive members of the public and suggests knowledge of BP influences BP control in this population.
CONFLICT OF INTEREST JS and MSK have no conflict of interest. PS and PB hold Department of Health Senior Fellowships.
& 2014 Macmillan Publishers Limited
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