(Hypertension. 1998;31:1014-1020.)
© 1998 American Heart Association, Inc.
Hypertension Optimal Treatment (HOT) Study
Home Blood Pressure in Treated Hypertensive Subjects
Sverre E. Kjeldsen;
Thomas Hedner;
Kenneth Jamerson;
Stevo Julius;
William E. Haley;
Miguel Zabalgoitia;
Amir R. Butt;
S. Noor Rahman;
Lennart Hansson;
; for the HOT Study Group
From the Division of Cardiology, Ullevaal University Hospital, Oslo,
Norway (S.E.K.); the Department of Clinical Pharmacology, Sahlgrenska
University Hospital, Gothenburg (T.H.); and Clinical Hypertension Research,
University of Uppsala, Uppsala (L.H.), Sweden; the Division of Hypertension,
University of Michigan Medical Center (Ann Arbor) (K.J., S.J.); Mayo Clinic,
Jacksonville, Fla (W.E.H.); the Division of Cardiology, University of Texas
Health Science Center at San Antonio (M.Z.); and the Division of Renal
Diseases and Hypertension, University of Texas Health Science Center at
Houston (A.R.B, S.N.R.).
Correspondence to Sverre E. Kjeldsen, MD, PhD, Division of Cardiology, Department of Internal Medicine, Ullevaal Hospital, N-0407 Oslo, Norway. E-mail sverrekj{at}ulrik.uio.no
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Abstract
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Abstract—The Hypertension Optimal
Treatment Study is a prospective trial conducted in 26 countries. The
aims are to (1) evaluate the relationship between three levels of
target office diastolic blood pressure (BP) (
80, 85, or
90 mm Hg) and cardiovascular morbidity and
mortality in hypertensive patients and (2) examine the effects on
cardiovascular morbidity and mortality of 75 mg aspirin
daily versus placebo. A total of 19 193 patients between 50 and 80
years of age had been randomized by the end of April 1994. Treatment
was initiated with felodipine 5 mg daily, and additional therapy was
given in accordance with a set protocol. The present substudy of
926 patients performed in nine countries aimed to (1) compare home with
office BP in a representative subsample of the HOT
population after the titration of treatment was completed and (2)
clarify whether the separation into the target groups could be expanded
into the out-of-office setting. The differences between office and home
measurements in diastolic BP of 0.2 mm Hg (SD, 9;
95% confidence interval, -0.36 to 0.81; P=.40) and
systolic BP of 0.5 mm Hg (SD, 15; 95% confidence
interval, -0.53 to 1.46; P=.21) were not significant.
The group differences in home BP were 1.9 mm Hg (80 versus
85) and 1.2 mm Hg (85 versus 90) for diastolic
BP (F=11.69; ANOVA, P<.0001) and 2.6 and 2.1
mm Hg for systolic BP (F=8.44, P=.0002). Thus,
office and home BPs measured with the same semiautomatic device are
comparable in treated hypertensive subjects in the HOT Study, and the
separation into the target groups based on office readings prevails
at home.
Key Words: antihypertensive agents • blood pressure monitoring • cardiovascular diseases • clinical trials • hypertension, white coat
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Introduction
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The Hypertension
Optimal Treatment (HOT) Study is a multicenter trial being conducted in
26 countries. The rationale and background have been described in
detail previously.1 The HOT Study is conducted in
accordance with the PROBE design.2 The main aim
is to evaluate the relationship between three levels of target
diastolic BP (80, 85, or 90 mm Hg) and
cardiovascular morbidity and mortality in hypertensive
patients. In addition, the study will examine the effects on morbidity
and mortality of a low dose (75 mg daily) of
acetylsalicylic acid or double-blind
placebo.1
When the inclusion of patients was stopped on April 30, 1994,
19193 patients between 50 and 80 years of age had been
randomized. Basic antihypertensive treatment was initiated with the
calcium channel blocker felodipine (5 mg daily). If target blood
pressure was not reached, additional antihypertensive therapy was given
in accordance with a set protocol.1 Details of
the patient characteristics at randomization,
cardiovascular risk profiles, and early BP results have
previously been published.3 4
Home BP monitoring can easily be taught and learned, and it has a high
reproducibility and sensitivity of
measurement.5 6 Because of the lack of
prospective mortality/morbidity data, home BP monitoring cannot be used
alone to decide whether treatment is indicated,7
and treatment decisions must still be based on repeated standard clinic
BP readings. Home BP has been investigated in a large study of
normotensive and untreated hypertensive
subjects.8 However, large studies of home BP in
treated hypertensive patients have not been done. This is particularly
feasible in the HOT Study because of the standardization of
measurements of BP with a semiautomatic device and the subsequent
possibility to train subjects at every office visit. Therefore, the aim
of the present study was to compare home BP with office BP in a
large and representative subsample of the HOT Study
population after the titration of antihypertensive treatment. The study
also aimed to clarify whether the separation of subjects into the three
main groups (80, 85, or 90 mm Hg) based on office readings
could be expanded into the out-of-office setting.
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Methods
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Subjects
In the main study, a total of 19193 hypertensive
patients of any race aged 50 to 80 years were randomized in 26
countries. Details of their characteristics at randomization have
previously been published.3 The average mean±SD
randomization BP in patients untreated at enrollment was
169±14/106±3 mm Hg; in the treated patients, after at least 2
weeks of washout, the mean±SD BP was 170±14/105±3 mm Hg. The
three target BP groups were well matched at the outset of the
study.3
There were no additional criteria for participation in the home BP
substudy except for patient willingness. For practical reasons, the
study was limited to 88 centers from a total of 1921 participating
centers in the HOT Study. The sample (n=926) that participated in the
substudy contained a higher percentage of previously treated subjects
(66% versus 52%); otherwise, characteristics were comparable with
those of the subjects in the main study (Table 1
). The distribution of the 926 patients
between countries was as follows: Canada 72, Greece 34, Hungary 36,
Israel 10, The Netherlands 19, Norway 109, Spain 124, Sweden 82, and
United States 440 patients.
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Table 1. Characteristics of Hypertensive Patients1
in the
Main Part of the HOT Study Compared With Subjects in the Home Blood
Pressure Substudy
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Protocol
Patients in the HOT Study were recruited after giving informed
consent provided that the substudy had been approved by the local
ethics committee in the respective country. BP was measured at
enrollment and then at two qualifying visits at least 7 days apart. The
diastolic BP had to be in the range of 
100 to 115
mm Hg at both qualifying visits. A number of exclusion criteria were
specified.1 All patients started active
antihypertensive treatment with felodipine, 5 mg once daily. In treated
patients, this was preceded by a washout period of at least 2 weeks. If
the target BP was not reached, additional antihypertensive therapy with
either an angiotensin-converting enzyme
inhibitor or a ß-adrenoceptor blocking agent was given.
Further dosage adjustments were made in accordance with a set
protocol.1 As a fifth and final step, a
diuretic could be added. After 6 months,3
the percentages of patients who had achieved their randomized target
clinic diastolic BP were 57%, 71%, and 83% for the
target groups at 80, 85, or 90 mm Hg, respectively, and
after 12 months they were 57%, 72%, and 84%,
respectively.4 The distribution of the dose steps
in the three target groups was fairly
similar.3 4
BP and HR have been measured in the sitting position with a newly
calibrated semiautomatic oscillometric device with a digital readout
(Visomat OZ, D2 International, Hestia Pharma GmbH). The accuracy of
this device has been extensively validated (in 407 normotensive and
hypertensive subjects) against standard sphygmomanometer readings
according to the recommendations of the British Hypertension
Society,9 with the conclusion that this device
provides accurate and reliable measurements of
BP.10 Measurements were done in the same arm each
time and with a cuff of appropriate size relative to the patient's
arm. The cuff was kept at the heart level, and the arm was supported at
the time of the measurement. In the office, three measurements were
made at least 15 seconds apart, after 5 minutes of rest, and the
averages were calculated for statistical analysis. Visits took
place at the same time of the day, usually in the morning, and the
measurements were performed at the end of the dosing interval by the
same person.
Home assessments were performed over 7 consecutive days with the same
kind of semiautomatic device after appropriate training of the
participating patients. After the subjects sat for 5 minutes, both in
the morning before leaving home and in the afternoon after returning
home, BPs and HR were taken three times, and the measurements were
registered on special case record forms. Conditions for
measurements were thus comparable at home and in the investigator's
office; however, measurements were not standardized for intake of
antihypertensive medication. The averages of all measurements at home
have been used for comparisons with the respective office measurements.
The averages of the morning measurements have also been compared with
the averages of the afternoon measurements.
Assessments of BP and HR at home were performed at a time when the
titration of antihypertensive medication in the study had been
finalized, ie, at least 6 months after randomization. An automatic
device was given to the patient after a scheduled visit for the
majority of patients at 6 (n=168), 12 (n=462), 18 (n=191), or 24 (n=67)
months; the home measurements were then performed shortly thereafter
(on average 4 days later) and in most subjects (n=890) on consecutive
days. In each patient, the data from the home assessments were compared
with BP and HR taken at the regular scheduled visit to the office of
the investigator that was nearest in time to, and usually preceded, the
home measurements. Nine patients were excluded from the home-office
comparison because the exact time for home measurements had not been
written on the registration form. One patient had not written the
diastolic BPs on the form, and four had not registered
HRs.
The home BP data was edited by one of the investigators (S.E.K.)
according to an a priori protocol for the purpose of cleaning the
data for clearly erroneous recordings. This was done before any
statistical analysis. Approximately 3% of all
recordings were considered erroneous (single numbers
incompatible with life or way out of range with all others in the same
patient, diastolic BP almost identical to systolic
BP or higher, HRs compatible with a paroxysmal
tachycardia); the accompanying BPs and HRs taken
simultaneously were deleted. Not all patients had all
measurements taken at all 14 occasions, leaving nearly 34000
measurements of both BPs and HR for analysis.
Statistics
To study the repeatability of the method, the within-individual
SD both in mm Hg and as a percentage of the total mean was
calculated. The average bias of one method relative to the other was
estimated by the mean difference and a 95% CI of the mean difference
between the two methods. To study how well the two methods were likely
to agree for an individual, the limit of agreement (mean±2 ·
SDiff) was calculated.11
For comparison between home and office BP, Wilcoxon's signed
rank test for matched pairs was used. Pearson correlation coefficients
(r) were calculated. Methods of BP measurement were also
compared by plotting the difference between two methods for each
subject against the average of BP measured by the two techniques. A
one-way ANOVA was used for the overall test between target groups.
Tukey-Kramer studentized range test12 was used
for pairwise post hoc comparisons between target groups.
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Results
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Within-individual SD for home BP for all patients (n=926) was as
follows for (1) calculations between all days: diastolic BP
4.7 mm Hg (5.7%), systolic BP 7.3 mm Hg (5.3%),
and HR 4.5 bpm (6.0%); (2) calculations between morning and afternoon
on the same day: diastolic BP 6.5 mm Hg (7.9%),
systolic BP 9.8 mm Hg (7.1%), and HR 6.6 bpm (8.8%);
and (3) calculations between three measurements at the same occasion:
diastolic BP 4.8 mm Hg (5.8%), systolic BP
7.8 mm Hg (5.7%), and HR 3.5 bpm (4.7%).
The difference found in diastolic BP of 0.2±9.0
mm Hg between home and office measurements was not statistically
significant (Table 2); neither could any
significant difference between home and office be related to previous
treatment status (treated versus untreated), age, race, or level of
serum cholesterol or serum creatinine at
randomization (data not shown). However, for the target group
randomized to clinic diastolic BP 90, there was a
slightly lower diastolic BP measured at home. This
difference between office and home readings was significant (Table 2),
as was the case for readings taken by female subjects (
1.16
mm Hg; 95% CI, 0.26 to 2.06 mm Hg; P=.003; n=418)
and patients with body mass index <28.1 kg/m2
(0.85 mm Hg; 95% CI, 0.00 to 1.70; P=.047;
n=395).
One-way ANOVA between the target groups showed differences for
diastolic BP measured in the office (F=30.93,
P<.0001), as well as at home (F=11.69,
P<.0001). For the three diastolic BP target
groups, the differences in office measurements between the groups were
3.0 mm Hg (80 versus 85, P<.05), 1.8 mm Hg
(85 versus 90, P<.05), and 4.8 mm Hg (80 versus
90, P<.05). These differences were fairly comparable to
the differences between the groups obtained during home BP
measurements: 1.9 mm Hg (80 versus 85, P<.05),
1.2 mm Hg (85 versus 90, NS), and 3.1 mm Hg (80
versus 90, P<.05), respectively.
The difference in systolic BP measured in the office compared
with at home averaged 0.5±15.3 mm Hg for all patients and was
not statistically significant (Table 2
). There were minimal differences
between office and home systolic BP measurements with respect
to previous treatment status, age, race, or level of serum
creatinine at randomization (data not shown). For the
treatment group targeted at 90 mm Hg, the lower
systolic BP at home compared with office was significant (Table 2), which was also the case for women (1.69 mm Hg; 95% CI,
0.13 to 3.25; P=.012; n=419), patients with body mass index
<28.1 kg/m2 (2.08 mm Hg; 95% CI, 0.58
to 3.58; P=.007; n=395), and patients with serum
cholesterol 6.1 mmol/L (1.58 mm Hg; 95%
CI, -0.09 to 3.26; P=.015; n=376).
One-way ANOVA between target groups showed differences for
systolic BP in the office (F=19.49, P<.0001) and at
home (F=8.44, P=.0002). For the three diastolic
BP target groups, the differences between the groups during office
measurements were 4.2 mm Hg (80 versus 85,
P<.05), 3.3 mm Hg (85 versus 90,
P<.05), and 7.5 mm Hg (80 versus 90,
P<.05), which is fairly comparable to the differences
between the groups during home BP measurements: 2.6 mm Hg (80
versus 85, P<.05), 2.1 mm Hg (85 versus 90,
NS), and 4.7 mm Hg (80 versus 90, P<.05),
respectively.
HR averaged 1.7 bpm higher in the office compared with at home (SD
8.6), and this difference, although rather small, was statistically
significant (Table 2). This office-home difference in HR was stable
among the three different BP target groups and in relation to the
various demographic variables at randomization (data not shown).
For the three diastolic BP target groups, the differences
in HR between the groups during office measurements were 1.7 bpm (80
versus 85, NS) and 0.5 bpm (85 versus 90, NS). These differences
were largely comparable to the differences between the groups during
home measurements: 1.8 bpm (80 versus 85, P<.05) and
0.3 bpm (85 versus 90, NS), respectively.
For all patients there were statistically significant correlations
(P<.0001 for all) between office and home measurements for
diastolic BP (r=.35), systolic BP
(r=.45), and for HR (r=.73). These correlations
are shown in Fig 1, whereas the plots of
the differences between office-home against the means of office and
home for each patient are shown in Fig 2.
The coefficients of regression for systolic BP
(P<.05) and for HR (P<.001) between differences
in office-home and mean (office-home) are significant. The variance
explained is 0.4% for systolic BP and 4% for HR.
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Figure 1. For all patients (n=914) these plots show
significant correlations (P<.0001 for all) between
systolic BP in the office and at home (r=.45), for
diastolic BP in the office and at home (r=.35), and
similarly for HR (r=.73).
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Figure 2. For all patients (n=914) these plots show the
differences between office-home against the means of office and home
for each patient. The standard deviations are drawn in.
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There was a significant (P<.0001) mean±SD decrease of
1.2±5.5 mm Hg in diastolic BP from morning
(83.1±8.4 mm Hg) to afternoon (81.9±8.2 mm Hg).
Corresponding values for systolic BP were 137.5±14.6 and
136.6±15.0 mm Hg (P<.001) and for HR 73.9±10.9 and
76.2±11.1 bpm (P<.0001). There were significant
correlations (P<.0001 for all) between average measurements
in the morning and in the afternoon for diastolic BP
(r=.78), systolic BP (r=.84), and HR
(r=.87) (Fig 3). Fig 4 shows the plots of the differences
between afternoon-morning against the means of afternoon and morning
for each patient. There are not any significant coefficients of
regression for BPs or HR between differences in afternoon-morning and
mean (afternoon-morning).
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Figure 3. For all patients (n=926) these plots show
significant correlations (P<.0001 for all) between
average measurements in the morning and in the afternoon for
systolic BP (r=.84), diastolic BP
(r=.78), and HR (r=.87).
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Figure 4. For all patients (n=926) these plots show the
differences between afternoon-morning against the means of afternoon
and morning for each patient. The standard deviations are drawn
in.
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The numbers of patients who had home and office BPs within ±10
mm Hg, home BP >10 mm Hg higher than office BP, and office BP
>10 mm Hg higher than home BP were 700, 98, and 116 for
diastolic BP and 477, 207, and 231 for systolic BP,
respectively.
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Discussion
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The present substudy to the HOT trial of 926 patients in nine
countries aimed to compare home BP with office BP in a
representative subsample after the titration of
treatment and to clarify whether the separation in main BP target
groups (80, 85, or 90 mm Hg) observed in the office could
be expanded into the out-of-office setting. Small office-home
differences in measured diastolic and systolic BPs
were not significant. However, HR was significantly higher in the
office compared with at home. For the three BP target groups, the
differences between the groups during home BP measurements were
1.9 mm Hg (80 versus 85) and 1.2 mm Hg (85 versus
90) for diastolic BP and 2.6 and 2.1 mm Hg for
systolic BP, respectively.
Some previous large-scale trials in mild-to-moderate
hypertension13 14 have undoubtedly included
substantial numbers of borderline and white coat hypertensive subjects
with low risk. Our results show that the patients in the HOT Study have
comparable treated ("target") BPs in the doctor's office and at
home based on self-measurements. Only when subgroups were
analyzed could some barely significant differences of minor
clinical relevance be found. These data suggest that the HOT Study
investigators randomized established hypertensive patients with high
risk and in need of antihypertensive therapy. In such a population of
middle-aged and elderly hypertensives, when judging from average
values, unexpectedly low out-of-office BPs are rare. Furthermore, it is
not hazardous to lower BP to the study target and even 80
mm Hg. Our results also show that separation into the three BP target
groups based on office readings prevails in the out-of-office setting,
which increases the likelihood of detecting differences between the
groups in cardiovascular events in the main HOT
Study.
Ambulatory BPs over 24 hours may be somewhat lower than self-measured
BP at home.15 16 17 18 The reason for this difference
seems to be that the former technique includes nighttime BP, which is
lower than daytime BP in most subjects.19 Awake
ambulatory BP, however, compares rather well to self-assessed home BP
in a large study,8 suggesting that the home BPs
measured in the present study, although not directly compared, are
representative for daytime BP.
Devices for home BP monitoring have been extensively tested. The
National High Blood Pressure Education Program of the United States
concluded20 that all three types of devices
(mercury, aneroid, and electronic) are reasonably accurate for home
use, provided they are properly calibrated and individuals using them
appropriately trained. However, Evans et al,21
who also tested a range of equipment types (mercury, aneroid, and
electronic), found that 11 (48%) of the 23 devices they tested were
inconsistent with duplicates of the same devices and failed the
standards for automated devices of the Association for the Advancement
of Medical Instrumentation. Fewer than 25% of the devices were
considered suitable for home use on the basis of accuracy, reliability,
and ease of use. Thus, care must be taken in the choice of device, and
training is required for all devices.21
In the present study, only newly calibrated devices were used, and
all subjects were properly trained for home BP measurements. To achieve
acceptable readings, the patients went through the measurement
procedure repeatedly at the clinic visits before taking home
measurements. The accuracy of the home measurements could be noted by
(1) the low within-individual SDs for home BP, (2) the
consistency of the main results with small variation of the
home findings and SDs compared with the office readings, and (3) the
rather strong correlations between morning and afternoon registrations
taken by the patients themselves.
Despite the higher HR measured in the office compared with at home,
there was no clear evidence in the HOT Study that the patients had any
white coat effect or alerting reaction on BP when in the treated state.
It may be possible that with treatment of more established
hypertension, as in the HOT Study, the difference between home and
office measurements decreases compared with other groups of
hypertensive patients.22 23 24 25 Thus, it would be
expected that the proportion of patients with white coat hypertension
and even white coat effect would be low. There is also a stability
factor of several months or years of evaluation that may have excluded
borderline or white coat individuals, and there may be a habituation to
office BP measurements with time.26 However, it
may also be speculated whether the use of a semiautomatic device with
digital readout by itself dampens the white coat effect and makes it
insignificant. If this is the case, this technique for measurement of
BP could preferentially be used in the screening for subjects in future
large-scale clinical hypertension trials.
In conclusion, office and home BPs are comparable in treated
hypertensive subjects in the HOT Study, and the separation into target
groups based on office readings prevails in the out-of office
setting.
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Selected Abbreviations and Acronyms
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| BP |
= |
blood pressure |
| CI |
= |
confidence interval |
| HOT |
= |
Hypertension Optimal Treatment Study |
| HR |
= |
heart rate |
| PROBE |
= |
Prospective Randomized Open Blinded End Point |
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Appendix 1
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The HOT Study is organized as follows: Executive
Committee: L. Hansson and A. Zanchetti (Chairmen), S.G.
Carruthers, K.H. Rahn, S. Julius, J. Ménard, H. Wedel, B.
Dahlöf, D. Elmfeldt, S. Westerling; Steering
Committee: D. Clement, Belgium, F. Fyhrqvist, Finland, B-G
Hansson, Sweden, H. Ibsen, Denmark, K. Jamerson, United States, S.E.
Kjeldsen, Norway, R. Kolloch, Germany, P. Larochelle, Canada, G.
Leonetti, Italy, G. McInnes, UK, J.-M. Mallion, France, T. Rosenthal,
Israel, L. Ruilope, Spain, F. Skrabal, Austria, P. Toutouzas, Greece,
B. Waeber, Switzerland, H. Wesseling, The Netherlands, J.-R. Zhu,
People's Republic of China; National Coordinators: R.
Sanchez, Argentina, E. Kékes, Hungary; Substudy
Committee: T. Hedner, G. Mancia, D. Elmfeldt; Safety
Committee: J.D. Swales, S. Pocock, J.L. Rodicio; Clinical
Event Committee: L. Rydén, C. DalPalù, H. Holzgreve;
Audit Committee: L.H. Lindholm, J.K. McKenzie;
Coordinating Group: J. Allgén, I. Warnold, S.
Westerling; Data Managers at Study Coordinating Center: J.
Lindquist, N-G. Pehrsson, A. Holmner, S. Lilja.
The following HOT investigators participate in the home BP substudy:
Canada (72 patients): S. Arndt, T. Atkinson, C. Caron, D.
Carswell, J. Cousill, D. Eddy, A. Kelly, R. Luton, P.P. Mohindra, S.
Nawaz, T. O'Callahan, D. Phaneuf, D. Ross, L. Salgado, D. Saunier, L.
Scholar, B. Thompson; Greece (34 patients): K. Kifnidis, C.
Panagoulis, K. Siamopoulos, D. Tsigas; Hungary (36
patients): C. Farsang, L. Matos, A. Tahy, I. Varga; Israel
(10 patients): A. Cantor, E. Paran; The Netherlands (19
patients): P.V.H.M. Bots, R. van Dehn, H.J.J. van der Heijden, K.J.
Lugtmeier, I.C. Spelled; Norway (109 patients): J. Bakken,
Ø. Berg, J.E. Billington, V. Borstad, T. Bredvold, A. Dehli, A.
Dyrdal, A. Fangberget, S. Hoff, H. Istad, M. Jervan, T. Kurås,
K. Michelsen, R. Nahoui, D. Nilsen, T. Risanger, T. Torjussen, E. Ture,
T. Tvedten, T. Uhre, M. Zennegg; Spain (124 patients): L.S.
Adite, G.G. Barrera, R.D. Belinchón, M.L. Broseta, F.L. Corral,
J. Closas, M.L.H. Elices, E.U. Fernández, M.A. Gertrudis, F.J.A.
Lara, A. Minguez, J.M.M. Muñoz, J.C.L. Peral, J.B. Rubio, J. de
Castro Simón, J. Soler, J.T. Tamarit, A. Valades, O.G. Vallejo,
J. Vila; Sweden (82 patients): A.-C. Barrie, H. Bjartell, G.
Ekblad, K. Juul, B. Nyman, M. Perkmar, B. Sjöblom, G.
Tygesén, B. Tyter; and United States (440 patients):
W.B. Haley, D.W. Jones, S. Oparil, N. Rahman, A.R. Butt, S. Yarows, M.
Zabalgoitia.
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Acknowledgments
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This work was supported in part by a grant-in-aid from Astra.
Nils-Gunnar Pehrsson at the HOT Coordinating Center at Östra
Hospital in Götenburg, Sweden, is acknowledged for data
processing and statistical work.
Received July 2, 1997;
first decision August 20, 1997;
accepted December 4, 1997.
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Abstract
Introduction
