| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(Hypertension. 1999;34:818-825.)
© 1999 American Heart Association, Inc.
Scientific Contributions |
From the Department of Cardiology, Asociación Española Primera de Socorros Mutuos, Montevideo, Uruguay.
Correspondence to Hypertension Working Group, Departamento de Cardiología, Asociación Española Primera de Socorros Mutuos, Br. Artigas 1436, Montevideo 11300, Uruguay. E-mail esandoya{at}netgate.com.uy
| Abstract |
|---|
|
|
|---|
Key Words: blood pressure monitoring, ambulatory reference values hypertension, white coat blood pressure monitoring population
| Introduction |
|---|
|
|
|---|
Evidence of the risks of arterial hypertension and the benefits of its treatment are based on casual blood pressure (BP) measurements.7 8 Nevertheless, BP can be measured in different environments (clinic, home, and workplace), by different personnel (physician, nurse, or patient), and with a conventional sphygmomanometer or ABP devices. This introduces the problem of the correspondence among BP values measured in these different ways and situations, with its practical implications in the usual care of normotensive and hypertensive individuals. Correlation among ABP and the remaining BP measurement methods have been published in the above referred studies, but no one has compared the BP measured by a physician at clinic with BP measured by a nurse at clinic or at home, self-measured BP, and 24-hour ABP in the same sample. The purpose of this study was to estimate normal values of 24-hour ABP in an Uruguayan population and to perform a direct comparison of ABP results with clinic (physician and nurse), home, and self-measured BP values.
| Methods |
|---|
|
|
|---|
190 000 individuals,
roughly representative of the 1 345 000 Montevideo
inhabitants. The study was planned and performed in the Department of
Cardiology. The study protocol was approved by the
Institutional Ethics Committee. In October 1995, we randomly selected
within 6 age strata a sample of 2650 subjects >19 years of age with no
upper age limit. The selected subjects were invited to participate in
the survey by telephone and/or by letter. When the study was finished,
in June 1998, we had recruited 2070 of them (78%). All the patients
gave informed consent to participate in the study.
Blood Pressure Measurements
The clinic BP measurements by physician and nurse and the home
BP measurement by nurse were performed from Monday to Friday, after
8:00 AM and before 7:00 PM, according to
standard recommendations,9 10 with a previously validated
semiautomatic blood pressure measuring machine (Omron
HEM-705CP).11 Subjects refrained from smoking, drinking
coffee or tea, or using other stimulants
30 minutes before arriving
at the outpatient clinic. In the clinic, in a quiet warm office, the
individual was seated with the back resting against the chair and the
arm bared and supported at heart level. After 5 minutes of rest, the
first BP reading was performed. During blood pressure measurement, the
individual was instructed not to speak. A nurse or physician performed
the measurement 3 times each, with
2 minutes between each
measurement. Pulse frequency, BP, and the time of each measurement were
registered. After a few minutes, BP was measured by a physician if the
first set of measurements were performed by a nurse or vice versa.
Clinic BP measurements were performed first by a physician in 41.4% of
the visits and by a nurse in 58.6% of the visits, with
35 minutes
between both sets of measurements. During the clinic visit, the
date and time of the home visit was arranged. At home, BP was measured
by a nurse 3 times after sitting at rest for 5 minutes, with
2
minutes between each measurement. ABP monitoring was performed with
Spacelab 90207 devices. The devices were attached before individuals
left the clinic and were programmed to measure BP at 20-minute
intervals between 7:00 AM to 11:00 PM and at
40-minutes interval during the night. Individuals were instructed to
keep a diary of their asleep and awake times. The ABP study was
accepted if
20 valid measurements were recorded, otherwise it was
repeated. Self-measurement was obtained twice at home in a subset of
577 individuals (from among the last 1716 recruited subjects) by manual
self-activated ABP machine in the early morning and in the
evening after
5 minutes of rest in the sitting position. This
measurement was incorporated to our study when we knew the design
of the PAMELA study.
Other Variables
Body weight and height were registered, and a 12-lead ECG was
performed. A set of standard questions related to the knowledge,
habits, and attitudes of the individuals and their physicians was asked
by nurses. Clinical records were screened by physicians searching
for previous BP values and possible drug treatments. Some of this data
will be reported elsewhere.
Statistical Procedures
Age was stratified into 10-year span strata. The first stratum
covered individuals 20 to 29 years of age, and the last one comprised
individuals >69 years of age. The casual BP (clinic physician, clinic
nurse, and home nurse) values used for calculations are averages of 3
successive measurements. The self-measured values are averages of a
morning and an evening measurement. Conventional descriptive statistics
for continuous variables and proportions were calculated when
appropriate and used throughout the study for results
presentation. Student's t test for independent
samples was applied to assess differences between strata. Student's
t test for differences was applied to compare results of
different measurement methods, and bivariate Pearson correlation
matrices were calculated to obtain the correlation coefficients among
them. Bivariate linear correlation-regression was performed to assess
the relationship between the results of diverse ABP measurement results
and the physician at clinic BP values that were taken as reference
ones. This technique was also used to estimate the age-related
variations of BP. Diagnostic break points in correspondence
with 140/90 mm Hg physician at clinic BP were calculated for the
various outputs of ABP measurement as the predicted values, which were
obtained by the following equations:
![]() |
![]() |
|
| Results |
|---|
|
|
|---|
In a subgroup of 577 subjects, self-measured BP was also available. Compared with the whole sample, this subgroup was younger (40.5 years), had fewer women (52.8%), and had similar BMI (26.5 kg/m2).
Blood Pressure Findings
The results of BP measurements on the whole sample are shown in
Table 1. Results of the subdivisions in
12 age and sex strata are shown in Table 2.
|
|
Casual Blood Pressure
Casual systolic blood pressure (SBP) showed a sustained
increase through increasing age strata independent of gender. Casual
diastolic blood pressure (DBP) increased in men 59 years of
age (0.51 mm Hg/y, 95% confidence limits [CLs]: 0.42 to 0.6)
and in women 69 years of age (0.32 mm Hg/year, 95% CLs 0.27 to
0.37), P<0.0001 in both cases. We observed a slight decline
in DBP in older individuals, which was steeper in men (-0.42
mm Hg/y, 95% CLs: -0.65 to 0.19; P<0.0002 versus
-0.04 mm Hg/y, P=NS in women). At all age strata,
casual BP was higher in men than women (P<0.05), except
those individuals >69 years (P=NS). Physician and nurse at
clinic BPs were significantly different, but the difference was
clinically unimportant. When the physician took the first set of
readings, the average BP values were 126/78 mm Hg by physician
and 121/76 mm Hg (lower) by nurse (P<0.0001).
When the nurse took the first set of readings, the average values
were 125/79 mm Hg by nurse and 123/78 mm Hg (lower) by
physician (P<0.0001). We found small although significant
(P<0.05) differences between clinic BP (nurse or physician)
and nurse at home BP.
Ambulatory Blood Pressure
When systolic and diastolic ABP were
incremented as a function of age, this increase was not as steep as
that observed with casual BP; 0.36 (95% confidence limits: 0.32 to
0.40) versus 0.75 mm Hg/y (95% confidence limits: 0.69 to 0.81)
SBP and 0.17 (95% confidence limits: 0.14 to 0.20) versus 0.24
mm Hg/y DBP (95% confidence limits: 0.20 to 0.28),
P<0.005 in both. In all cases, the Pearson bivariate
correlation between clinic physician BP, clinic nurse BP, home nurse
BP, 24-hour ABP, and daytime ABP was >0.75 for SBP and >0.65 for DBP
(P<0.0001 in all). Nighttime ABP also significantly
correlated with r values >0.64 for SBP and >0.54 for DBP.
In the group as a whole, casual SBP and DBP were significantly higher
than 24-hour ABP, with a higher difference observed in men (8 to
10 mm Hg) than in women (5 to 7 mm Hg), P<0.05.
Daytime ABP was also lower than casual BP (P<0.05). In
women, this effect was not observed or, if it was, it was clinically
unimportant. When we analyzed the differences between casual
and ABP by gender and age strata, we observed similar systolic
values (or clinically unimportant differences) in women <50 years of
age and in men <40 years of age and similar diastolic
values in women <40 years of age and in men <30 years of age. Larger
differences were observed in women >49 years of age and in men >39
years of age, with the differences higher in men (P<0.05).
Table 3 shows the predicted values of ABP
that correspond to 140/90 mm Hg of physician BP as estimated by
first-degree linear regression analysis when the individuals
were classified by age and gender. The normal upper limits of mean
24-hour ABP in the whole sample (the predicted values that corresponded
to the traditional break points of 140/90 mm Hg) were 125/80
mm Hg (95% CLs: 124.5 to 125.5/79.6 to 80.4 mm Hg), with
variations between 122 to 128 mm Hg for SBP and 77 to 83
mm Hg for DBP related to gender and age. The normal upper limits of
daytime ABP in the whole sample were 129/84 mm Hg (95% CLs:
128.4 to 129.6/83.3 to 84.7 mm Hg), with age and gender-related
variations between 127 to 132 mm Hg for SBP and 81 to 86
mm Hg for DBP.
|
Self-Measurement of Blood Pressure
The observed BP values in the subgroup with self-measurement are
shown in Tables 4 (global) and
5 (by gender and age). Self-measured BP
and 24-hour ABP were very close (except in individuals >69 years of
age, in which only 5 individuals performed the self-measurement).
Differences between casual BP, self-measured BP, and 24-hour ABP were
smaller in women than in men (P<0.05) and smaller than the
lower BP values (P<0.05). In all cases, the Pearson
bivariate correlation between clinic physician BP, clinic nurse BP,
home nurse BP, self-measured BP, 24-hour ABP, and daytime ABP was
>0.60 for SBP and >0.50 for DBP (P<0.001 in all). In
addition, nighttime ABP significantly correlated with r
values >0.64 for SBP and >0.59 for DBP. Self-measured BP and 24-hour
ABP were significantly correlated with r>0.79 for SBP and
r>0.69 for DBP (P<0.001 in both). Table 6 compares our results with those from
other ABP population studies.
|
Physician measured BP
140/90 mm Hg was present in 26.1% of
the sample (as stated, subjects under antihypertensive therapy were
excluded in this study). Prevalence rose to 33.2% if calculated on the
2070 surveyed subjects (BP
140/90 mm Hg or antihypertensive
therapy).
| Discussion |
|---|
|
|
|---|
Casual SBP increased with age independent of gender. Casual DBP increased at the ages 69 and 59 years in women and men, respectively; after these ages, we observed a decline. In agreement with other studies, men had significantly higher casual BPs than women,6 except in individuals >69 years of age. We observed no difference in clinic BP whether it was measured by physician (124/79 mm Hg) or by nurse (123/78 mm Hg), but we observed BP differences related to the order in which measurements were performed. When BP was first measured by a physician, the mean BP values were higher than those obtained by the nurse (126/78 versus 121/76 mm Hg); when the first measurement was performed by a nurse, the mean BP values were slightly higher than those read by physician (125/79 versus 123/78 mm Hg). Thus, the effect of the order in which the BP measurements are performed could be more important that the role of the person who performs them. These results are different than those observed in other studies. This could be explained by different environmental conditions (early evidence on the white coat phenomenon was obtained through measurements performed at a hospital),12 social prestige of physicians and nurses in different countries, and nontypical ambulatory medical practice conditions in this survey. BP measurements at home by nurses showed slightly higher values than those obtained at clinic by physician and by nurse, mainly SBP in young people, but these differences are not clinically important. ABP and home values were similar to those observed in the Belgian study.
We found that the 24-hour ABP average value of 125/80 mm Hg (95% CLs: 124.5 to 125.5/79.6 to 80.4) is the upper limit for discrimination between normal and hypertensive individuals that best correlates with 140/90 mm Hg on casual BP measurements. These ABP normality values that ranged from 122 mm Hg (younger women) to 128 mm Hg (older men) for SBP and 77 mm Hg (20 to 29 years) to 83 mm Hg (50 to 59 years men) for DBP are shown in Table 3. Daytime limits were 127 to 131 mm Hg for SBP and 81 to 86 mm Hg for DBP. To assess the relationship between casual BP and ABP, we choose 140/90 mm Hg as a well-established upper limit for clinic BP normality, which was used in the PAMELA study. With the use of these upper limits of normal ABP, white coat hypertension was present in 23.3% of our sample. If 135/85 mm Hg was used as the normal upper limit, the prevalence of white coat hypertension would rise to 50.2%.
We observed ABP values identical to those of the PAMELA study, and ABP values almost identical to those shown in other ABP population studies (Table 6), except for the Danish study. In the Danish study, a higher 24-hour SBP was observed, which is possibly related to the cold climate and older age of participants. In the Japanese study, the individuals, although older, showed a lower BMI than that found in the subjects of other studies including ours. Other small differences could be explained by different ages or gender proportions in the studies. In the PAMELA study, the clinic BP was slightly higher than our observations; this could be because in the Italian study, BP was only measured in the clinic in morning when, according to known circadian patterns, BP reaches high values. This small difference could also be due to the different proportion of individuals receiving antihypertensive therapy among the samples, which was higher in our population (348/1921) than in the PAMELA study (213/1651), P<0.0001. We found that 24-hour ABP values were lower than casual BP values in subjects, except in younger subjects, in whom similar values, or clinical unimportant differences, were observed. Daytime and nighttime periods for ABP analyses were defined according to the patient's diary, instead of arbitrarily established periods, and this could explain the small differences observed with the other population studies. In contrast with results observed in the PAMELA study, in which differences between 24-hour ABP and self-measured increased with age, we did not observed such increases, but our data could be biased by the underrepresentation of older individuals in the self-measurement subgroup.
Self-measured BP was lower than home BP measured by nurse and very close to 24-hour ABP, which was similar to results reported in the PAMELA study. The self-measurement subgroup was younger than the entire population; this fact could explain the lower BP values observed and the differences between casual, self-measured, and 24-hour ABP. The self-measurement was performed when the participants activated the ambulatory device. This procedure has the advantage of eliminating the interdevice sources of error. Another potential bias source is related to inter-arm differences in BP, which was also eliminated in our study. Nevertheless, the procedure used for self-measurement of BP had the disadvantage of being under used by older subjects.
This is the first ABP population study that performed a direct comparison between physician at clinic BP, nurse at clinic BP, nurse at home BP, 24-hour ABP, daytime ABP, and self-measured BP (the last one in a subgroup). This direct comparison in a large study shows that clinic BP is similar when measured by nurse or by physician, and the differences between them are related to the sequence of measurements and not to the person that performs the measurement. This comparison also shows that home BP measured by nurse is similar to clinic BP and higher than self-measured BP. These results are clinically relevant because they mean that nurse or physician BP readings are equivalent for usual practice. Normal BP values of 140/90 mm Hg are adequate for nurse readings at home but too high for self-measured BP. Our data show that in an adult randomly selected population, in which individuals receiving antihypertensive therapy are excluded, a 24-hour ABP upper limit of normality is 125/80 mm Hg, which is similar to self-measured BP and lower than physician or nurse measured BP.
In conclusion, our study shows that 24-hour ABP average values of 125/80 mm Hg and daytime ABP average values of 129/84 mm Hg are suitable upper limits for normality. Higher limits would yield an artificially higher prevalence of white coat hypertension. Most subjects showed higher blood pressure levels when measurements were performed by healthcare personnel at clinic or at home than when self-measured at home. Our data on the relationships between casual BP and ABP readings confirm most results published to date and show the marked similarity between groups from all over the world. This data should be considered in everyday practice when several BP measurement methods are available. The present population is now being further followed to assess normal ABP values, taking into account the incidence of cardiovascular events.
|
|
| Acknowledgments |
|---|
Received May 8, 1999; first decision June 15, 1999; accepted July 26, 1999.
| References |
|---|
|
|
|---|
2.
Imai Y, Nagai K, Sakuma M, Sakuma H, Nakatsuka H,
Satoh H, Minami N, Munakata M, Hashimoto J, Yamagishi T, Watanabae N,
Yabe T, Nishiyama A, Abe K. Ambulatory blood pressure of adults in
Ohasama, Japan. Hypertension. 1993;22:900912.
3. O'Brien E, Murphy J, Tyndall A, Atkins N, Mee F, McCarthy G, Staessen J, Cox J, O'Malley K. Twenty-four-hour ambulatory blood pressure in men and women aged 17 to 80 years: the Allied Irish Bank Study. J Hypertens. 1991;9:355360.[Medline] [Order article via Infotrieve]
4. Staessen J, Fagard Rh, Lijnen PJ, Thijs L, Van Hulle S, Vyncke G, Amery A. Ambulatory blood pressure and blood pressure measurement at home: progress report on a population study. J Cardiovasc Pharmacol. 1994;23(suppl 5):S5S11.
5. Mancia G, Sega R, Bravi C, De Vito G, Valagussa F, Cesana G, ZanchettiA. Ambulatory blood pressure normality: results from the PAMELA study. J Hypertens. 1995;13:13771390.[Medline] [Order article via Infotrieve]
6. Rasmussen SL, Torp-Pedersen C, Borch-Johnsen K, Ibsen H. Normal values for ambulatory blood pressure and differences between casual blood pressure and ambulatory blood pressure: results from a Danish population survey. J Hypertens. 1998;16:14151424.[Medline] [Order article via Infotrieve]
7. MacMahon S, Peto R, Cutler J, Collins R, Sorlie P, Neaton J, Abbott R, Godwin J, Dyer A, Stamler J. Blood pressure, stroke, and coronary heart disease, I: prolonged differences in blood pressure: prospective observational studies corrected for the regression dilution bias. Lancet. 1990;335:765774.[Medline] [Order article via Infotrieve]
8. Collins R, Peto R, MacMahon S, Hebert P, Fiebach NH, Eberlein KA, Godwin J, Qizilbash N, Taylor JO, Hennekens CH. Blood pressure, stroke, and coronary heart disease, II: short-term reductions in blood pressure: overview of randomized drug trials in their epidemiological context. Lancet. 1990;335:827838.[Medline] [Order article via Infotrieve]
9. Perloff D, Grim C, Flack J, Frohlich ED, Hill M, McDonald M, Morgenstern BZ. Human blood pressure determination by sphygmomanometry. Circulation. 1993;88(pt 1):24602470.
10. American Society of Hypertension. Recommendations for routine blood pressure measurement by indirect cuff sphygmomanometry. Am J Hypertens.. 1192;5:207209.[Medline] [Order article via Infotrieve]
11. Grupo de Hipertensión. Asociación Española. Validación de un equipo electrónico para medir la presión arterial. Rev Urug Cardiol. 1996;11:9093.
12.
Mancia G, Parati G, Pomidosi G, Grassi G, Casadei R,
Zanchetti A. Alerting reaction and rise in blood pressure during
measurement by physician and nurse. Hypertension. 1987;9:209215.
This article has been cited by other articles:
![]() |
A. Adiyaman, D. G. Dechering, J. Boggia, Y. Li, T. W. Hansen, M. Kikuya, K. Bjorklund-Bodegard, T. Richart, L. Thijs, C. Torp-Pedersen, et al. Determinants of the Ambulatory Arterial Stiffness Index in 7604 Subjects From 6 Populations Hypertension, December 1, 2008; 52(6): 1038 - 1044. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. W. Hansen, L. Thijs, J. Boggia, Y. Li, M. Kikuya, K. Bjorklund-Bodegard, T. Richart, T. Ohkubo, J. Jeppesen, C. Torp-Pedersen, et al. Prognostic Value of Ambulatory Heart Rate Revisited in 6928 Subjects From 6 Populations Hypertension, August 1, 2008; 52(2): 229 - 235. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. M. Cusumano and M. C. Gonzalez Bedat Chronic Kidney Disease in Latin America: Time to Improve Screening and Detection Clin. J. Am. Soc. Nephrol., March 1, 2008; 3(2): 594 - 600. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Kikuya, T. W. Hansen, L. Thijs, K. Bjorklund-Bodegard, T. Kuznetsova, T. Ohkubo, T. Richart, C. Torp-Pedersen, L. Lind, H. Ibsen, et al. Diagnostic Thresholds for Ambulatory Blood Pressure Monitoring Based on 10-Year Cardiovascular Risk Circulation, April 24, 2007; 115(16): 2145 - 2152. [Abstract] [Full Text] [PDF] |
||||
![]() |
K M English Stenting the mildly obstructive aortic arch: useful treatment or oculo-inflatory reflex? Heart, November 1, 2006; 92(11): 1541 - 1543. [Full Text] [PDF] |
||||
![]() |
L. Quaranta, F. Gandolfo, R. Turano, F. Rovida, T. Pizzolante, A. Musig, and E. Gandolfo Effects of Topical Hypotensive Drugs on Circadian IOP, Blood Pressure, and Calculated Diastolic Ocular Perfusion Pressure in Patients with Glaucoma. Invest. Ophthalmol. Vis. Sci., July 1, 2006; 47(7): 2917 - 2923. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Sega, R. Facchetti, M. Bombelli, G. Cesana, G. Corrao, G. Grassi, and G. Mancia Prognostic Value of Ambulatory and Home Blood Pressures Compared With Office Blood Pressure in the General Population: Follow-Up Results From the Pressioni Arteriose Monitorate e Loro Associazioni (PAMELA) Study Circulation, April 12, 2005; 111(14): 1777 - 1783. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. I. Feig and R. J. Johnson Hyperuricemia in Childhood Primary Hypertension Hypertension, September 1, 2003; 42(3): 247 - 252. [Abstract] [Full Text] [PDF] |
||||
![]() |
F. Fontana, P. Bernardi, G. Lanfranchi, M. S. Pisati, and E. Merlo Pich Blood Pressure Response to Hyperventilation Test Reflects Daytime Pressor Profile Hypertension, February 1, 2003; 41(2): 244 - 248. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Hypertension Home | Subscriptions | Archives | Feedback | Authors | Help | AHA Journals Home | Search Copyright © 1999 American Heart Association, Inc. All rights reserved. Unauthorized use prohibited. |