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Systolic vs Diastolic Blood Pressure Control in the Hypertensive Patients of the PAMELA Population
Giuseppe Mancia, MD;
Michele Bombelli, MD;
Arturo Lanzarotti, MD;
Guido Grassi, MD;
GianCarlo Cesana, MD;
Alberto Zanchetti, MD;
Roberto Sega, MD
Arch Intern Med. 2002;162:582-586.
ABSTRACT
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Background Previous studies have shown that in the treated fraction of the hypertensive
population, blood pressure (BP) control is less common for systolic BP (SBP)
than for diastolic BP (DBP) as measured in the physician's office. Whether
this phenomenon is artifactually attributable to a temporary increase in BP
owing to a "white-coat" effect or represents a true rarity of SBP control
in daily life is unknown.
Methods Data were obtained from the PAMELA (Pressioni Arteriose Monitorate E
Loro Associazioni) study population, which involved individuals ranging in
age from 25 to 74 years who were representative of the residents of Monza
(a city near Milan, Italy) and who were stratified according to sex. Office
(an average of 3 sphygmomanometric measurements), home (an average of morning
and evening self-measurements using a semiautomatic device), and 24-hour ambulatory
(average of measurements performed every 20 minutes during the day and at
night) BP values were obtained in all study subjects. In the treated hypertensive
patients, BP was regarded as controlled if office values were less than 140
(SBP) or 90 (DBP) mm Hg. Home and 24-hour average SBP and DBP were regarded
as controlled if the values were lower than 132/83 and 125/79 mm Hg, respectively.
Results In the study participants (n = 2051), the number of patients with hypertension
who were receiving antihypertensive treatment was 398, or approximately 42%
of all individuals with hypertension. In-office SBP control by treatment was
less frequent than DBP control (29.9% vs 41.5%, P<.05).
This was also the case when home and 24-hour SBP and DBP control was considered
(38.3% vs 54.6% and 50.8 vs 64.9%, respectively, P<.05
for both).
Conclusions In the PAMELA population, SBP control by treatment was much less frequent
than DBP control by treatment. This was the case not only for office BP values
but also for home and 24-hour BP values, demonstrating that inadequate SBP
control is not limited to artificial BP-measuring methods but occurs in daily
life.
INTRODUCTION
SEVERAL STUDIES performed in a variety of countries have shown that
blood pressure (BP) values are satisfactorily controlled by treatment in only
a small fraction of the hypertensive population.1-9
Some of these studies have also shown that control by treatment is even less
common for systolic BP (SBP) than for diastolic BP (DBP); ie, that in a number
of patients, DBP values are lower than 90 mm Hg, while SBP values remain above
140 mm Hg.10-12
This finding has important adverse implications for public health, because
in the general population SBP has been shown to be an equal or even more important
cardiovascular risk factor than DBP.13-14
Furthermore, in elderly individuals with hypertension, a reduction in SBP
by treatment has often been shown to be a more important determinant of a
patient's protection from cardiovascular disease than a reduction in DBP.15
We previously showed that a noticeable number of patients with hypertension
in an urban population living in a town (Monza) northeast of Milan, Italy,
were untreated and that among those who were treated only a small percentage
had office BP values that were lower than 140/90 mm Hg, as has been documented
in other countries.16 Herein we report the
results obtained by analyzing the status of SBP control vs DBP control by
treatment in the hypertensive fraction of the same population. This analysis
provided data on SBP and DBP control based not only on office values but also
on home and ambulatory BP values, which enabled us to determine the degree
of SBP and DBP control in conditions of daily life.
SUBJECTS AND METHODS
The data reported herein originate from the PAMELA (Pressioni Arteriose
Monitorate E Loro Associazioni) study, which was performed to gather information
on the normal values of ambulatory and home BP in a representative sample
of the population of Monza, a town in the northeast district of Milan, Italy.
The methodological aspects of the PAMELA study have been reported elsewhere.16-19 Briefly,
3200 individuals aged 25 to 74 years were selected from the Monza residents
according to the age (decades), sex, and socioeconomic criteria of the World
Health Organization's MONICA (Monitoring Trends and Determinants in Cardiovascular
Disease) Project, which was performed in the same geographical area.20 The individuals selected were asked by letter to
report to the local hospital on a workday morning (Monday-Friday). The participants
were interviewed and visited so that demographic data could be recorded and
information on medical history, lifestyle, cardiovascular risk factors, and
diseases could be obtained. The same information was obtained from nonparticipants
who were interviewed by telephone and found to be similar to the participants
in age, sex, socioeconomic status, and prevalence of cardiovascular risk and
diseases. A trained physician measured the participants' sitting BP 3 times
using a mercury sphygmomanometer. The sitting BP was further measured (1)
over 24 hours with an oscillometric device model 90207; SpaceLabs Inc, Redmond,
Wash) that was programmed to start the monitoring period after completion
of the office BP measurements and to automatically read BP every 20 minutes21 and (2) in the morning and in the evening at home
with a semiautomatic oscillometric device (model HP 5331; Philips, Tokyo,
Japan) whose cuff had to be positioned on the arm contralateral to that used
for ambulatory BP monitoring. The participants had to record the values shown
on the digital display of the device in a diary and give it to the investigator.
A similar number of subjects were studied during the 4 different seasons and
during the 5 different workdays.19
For each participant, the 3 clinic BP values and the 2 home BP values
were averaged, with the SBP and DBP values being averaged separately. Ambulatory
SBP and DBP values were edited from artifacts21
and averaged over the 24 hours. There were 2051 participants in the study
(64.1% of the overall sample). Home BP values were available for 1867 subjects.
Ambulatory BP data were available for 2027 subjects and were found to be adequate
(at least 70% of the 72 readings over the 24 hours were valid) in 96% of the
subjects. In the group as a whole, the valid SBP and DBP readings were 94.7%
± 2.4% (mean ± SD) and 93.5% ± 2.2%, respectively, of
the 72 readings during the 24-hour period.
The subjects with hypertension were classified as unaware or untreated
if (1) the office BP value was greater than or equal to 140 mm Hg systolic
and/or 90 mm Hg diastolic, (2) the home BP value was greater than or equal
to 132 mm Hg systolic and/or 83 mm Hg diastolic, and (3) the 24-hour average
BP value was greater than or equal to 125 mm Hg systolic and/or 79 mm Hg diastolic
with no history of antihypertensive drug treatment in the preceding 15 days.
Selection of the home and ambulatory BP values was based on previous calculation
of the upper limit of normal of the home and 24-hour average BP values for
the whole PAMELA population.17 The subjects
with hypertension were classified as treated, regardless of the BP values,
if current antihypertensive drug treatment was reported. They were further
classified as treated with SBP and DBP control if the report of current antihypertensive
treatment was accompanied by an office SBP value of less than 140 mm Hg and
an office DBP of less than 90 mm Hg, respectively. The SBP or DBP control
was also established by home (systolic, <132 mm Hg; diastolic, <83 mm
Hg) and 24-hour average (systolic, <125 mm Hg; diastolic, <79 mm Hg)
BP values. Antihypertensive treatment was reported to consist of the use of
a diuretic (23%), a  -blocker (8%), a calcium antagonist (9%), an angiotensin-converting
enzyme inhibitor (18%), or a combination of 2 drugs or other treatments (42%).
Data were also analyzed in a similar fashion for groups of different
age ranges (25-49, 50-64, and 65-74 years) and for men and women. Mean ±
SD values from the various groups were compared by 2-way analysis of variance
using the t test for unpaired observations and the
Bonferroni correction for multiple comparisons to locate between-group differences.
A P value of .05 was taken as the level of statistical
significance.
RESULTS
In the PAMELA population, the percentage of subjects with an increase
in office BP values who were unaware of their status or untreated was 26.6%
of the overall number of subjects in whom office measurements were available.
The corresponding figures for home and 24-hour BP values were 22.1% and 22.1%,
respectively.
The number of subjects with hypertension who were treated was 398. As
shown in Figure 1, (1) office SBP
and DBP values were controlled in only 21.1% of the cases and (2) SBP control
was less frequent than DBP control. Although the percentages were somewhat
greater (Figure 1), similar findings
were observed when SBP and DBP control was based on home and 24-hour BP values.
This observation is further illustrated in Figure 2 which shows individual office, home, and 24-hour BP values
in the treated subjects with hypertension. Figure 3 and Figure 4
show the data separately for sex and age. For office, home, and 24-hour BP
values, systolic control was invariably less frequent than diastolic control
in both women and men (Figure 3).
Office, home, and 24-hour SBP control became progressively less frequent as
age increased (Figure 4), whereas
DBP control did not show any age-related change.
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Figure 1. The white part of the circles
represents the percentage of treated hypertensive subjects in the PAMELA (Pressioni
Arteriose Monitorate E Loro Associazioni) population with both systolic (S)
and diastolic (D) blood pressure (BP) control, SBP control only, and DBP control
only. The shaded part of the circle represents the percentage of treated hypertensive
subjects with uncontrolled SBP and DBP, SBP only, or DBP only. Control was
defined based on upper limits of office BP values (S,  140 mm Hg; D, 90
mm Hg), home BP (S, 132 mm Hg; D, 83 mm Hg) or 24-hour average BP
values (S, 125 mm Hg; D, 79 mm Hg). The upper limits of home and 24-hour
average BP values were derived from previous analysis of the data from the
entire population. There were 398 treated hypertensive subjects, 339 and 390
of whom also underwent monitoring of home and 24-hour average BP values, respectively.
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Figure 2. Individual systolic (S) and diastolic
(D) blood pressure (BP) values in all treated hypertensive subjects of the
PAMELA (Pressioni Arteriose Monitorate E Loro Associazioni) study. The horizontal
and vertical lines indicate the upper normal limits for office, home, and
24-hour SBP and DBP values.
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Figure 3. Percentage of treated hypertensive
men and women (HTs) with systolic (S) or diastolic (D) blood pressure (BP)
control based on office, home, or 24-hour values.
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Figure 4. Percentage of treated hypertensive
patients (HTs) with systolic (S) or diastolic (D) blood pressure (BP) control
grouped according to 3 different age ranges.
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COMMENT
The PAMELA study has shown that in subjects who were identified as hypertensive
by screening a large sample of an urban population living in the northeast
district of Milan, BP control by treatment is rare.16
It has also shown that this is the case not only for office values but also
for home and ambulatory values; therefore, this phenomenon is attributable
not to a "white-coat" effect causing a temporary increase in BP22
but to a true rarity of BP control in daily life. The present analysis of
the PAMELA data adds 2 pieces of evidence to these results: (1) the rare BP
control of the treated hypertensive subjects of the PAMELA population is more
commonly attributable to an inadequate reduction of SBP than of DBP; (2) once
again, the rare BP control involves not only office values but home and ambulatory
BP values as well. Therefore, we may conclude that in the hypertensive fraction
of the PAMELA population (1) an effective decrease in SBP is unquestionably
less common than an effective reduction of DBP and (2) this also occurs when
BP is measured at home or in ambulatory conditions, thus indicating that SBP
control is indeed less common than DBP control in daily life.16
Our data are in line with the results of previous studies that have
also observed a less frequent SBP than DBP control in treated patients with
hypertension, although data were based only on office BP values.10-12
Therefore, it is important to discuss 2 possible explanations for a phenomenon
that mainly accounts for the poor rate of overall BP control that has consistently
been reported in various populations. One explanation is that current hypertensive
drugs are less effective in lowering SBP than DBP, because the alteration
involved in an SBP elevation, ie, an increase in arterial stiffness,23 is less easily reversible than the alteration that
is involved in a DBP elevation, ie, an increase in arteriolar resistance to
blood flow.23 The second explanation is that
physicians titrate antihypertensive treatment of DBP and terminate further
therapeutic efforts once DBP values are lower than 90 mm Hg, even when SBP
values are higher than 140 mm Hg. It should be emphasized that both these
explanations may be valid, because large-scale studies of isolated systolic
hypertension have shown that drug treatment based on SBP reduction rarely
lowers SBP values below 140 mm Hg.24-26
Furthermore, in the large number of patients with systodiastolic hypertension
who were recruited for the Hypertension Optimal Treatment (HOT) study,27 a reduction of DBP well below 90 mm Hg (average value,
83 mm Hg) was achieved, even when the SBP remained above 140 mm Hg. This finding
was also noted among the hypertensive patients in the International Nifedipine
GITS (gastrointestinal therapeutic system) Study: Intervention as a Goal in
Hypertension Treatment (INSIGHT) study, in which the average DBP value was
reduced by treatment to 82 mm Hg, while the SBP value remained only slightly
below 140 mm Hg.28 This finding suggests that
DBP control may be achieved at smaller doses and/or with a lesser number of
drugs than SBP control, which may require more aggressive drug treatment.
Several other points deserve to be mentioned. First, in the PAMELA study
office, home and ambulatory SBP control was less frequent than DBP control
in both treated men and treated women. By and large, however, BP control was
more frequent in women than in men. This outcome confirms and extends the
results of previous studies that were based only on office BP values,10-12 which have suggested
this phenomenon to be attributable not to a sex difference in the efficacy
of antihypertensive drugs but to a greater compliance by women to antihypertensive
treatment. Second, in the PAMELA study patients, the percentage of treated
subjects with SBP control was progressively less from the youngest to the
oldest age stratum, regardless of whether office, home, or ambulatory BP was
considered. This result is unlikely to be accounted for by the fact that the
compliance of elderly patients to treatment is less than that of younger patients,
because DBP control was similar at all ages. It is more likely to depend on
the fact that (1) physicians may adopt a less aggressive therapeutic attitude
when they face a BP increase in the elderly (because of lack of full perception
of its risk and/or fear of a "J curve" phenomenon) and (2) in the elderly
the BP increase is more frequently systolic, ie, the component of the BP profile
that may be more difficult to normalize, possibly because of the limited reversibility
of an increase in arterial stiffness. Third, in the treated hypertensive patients
of the PAMELA population, SBP and DBP were more frequently found to be controlled
when home or ambulatory rather than office BP normalization was considered,
despite the very stringent criteria adopted to define the normal values for
home and ambulatory BP.17 This result may depend
on the fact that in some patients office BP may appear not to be normalized
by treatment because of the temporary increase in BP values that is caused
by a white-coat effect.22 Thus, when the prevalence
of uncontrolled hypertension in a population is being investigated, office
BP measurements may be complemented by BP measurements obtained outside the
office to avoid an overestimation as a result of this phenomenon.
The very low frequency of SBP control in the hypertensive population
has an obvious adverse significance for public health. Because SBP is now
recognized as being an equal or even more important cardiovascular risk factor
than DBP,13-14 its more common
lack of control means that the population in general will remain at a high
risk for cardiovascular complications. Furthermore, a more common reduction
in DBP values than in SBP values induces an increase in pulse pressure, ie,
an increase in a variable that has recently been shown to be a possible independent
risk factor for cardiovascular disease.29
AUTHOR INFORMATION
Accepted for publication July 17, 2001.
Corresponding author and reprints: Giuseppe Mancia, MD, Clinica Medica,
Università di Milano-Bicocca, Ospedale San Gerardo, Via Donizetti 106,
20052 Monza, Italy.
From Clinica Medica (Drs Mancia, Bombelli, Lanzarotti, Grassi, and
Sega) and Clinica del Lavoro (Dr Cesana), Università di Milano-Bicocca,
Ospedale San Gerardo, Monza, Italy; and Istituto Auxologico Italiano (Drs
Mancia, Grassi, and Zanchetti) and Centro Fisiologia Clinica e Ipertensione,
Università Milano (Drs Mancia, Grassi, and Zanchetti), Milano, Italy.
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