(Hypertension. 1998;32:377-378.)
© 1998 American Heart Association, Inc.
Effect of Daytime Sleep on Blood Pressure Monitoring in HARVEST Study Results
Michael Bursztyn
Hypertension Unit, Department of Medicine,
Hadassah University Hospital, Mount-Scopus,
Jerusalem, Israel
To the Editor:
In their recent report on target organ damage in white coat and
sustained stage I hypertensive subjects from the HARVEST study,
Palatini et al1 have made a significant
contribution by applying different cutoff points for normotension and
by matching for ambulatory blood pressure of the normotensives and
white coat hypertensives by one of the chosen values. Nevertheless,
there is still one caveat. By choosing daytime instead of 24-hour
ambulatory blood pressure, Palatini et al ignore the potential
contribution to blood pressure load of nocturnal blood pressure.
Perhaps even more important is the potential confounding effect of the
siesta (daytime sleep, afternoon nap), which is not an uncommon
practice in the Mediterranean area (including Italy, where the
above-mentioned study took place), Latin America, and other countries.
We have found that 30% of those referred for 24-hour ambulatory blood
pressure monitoring follow the practice of the
siesta.2 Inclusion of daytime-sleep blood
pressure in daytime blood pressure significantly diminishes its average
value.2 3 4 5 This is because during the siesta, in
our2 3 4 and other
studies,5 6 blood pressure declines to nocturnal
levels. If the prevalence of the siesta is not evenly distributed
between normotensives, white coat, and sustained hypertensives, it may
affect the HARVEST study results, since the normotensive subjects in
that study (medical staff and their relations) may be quite different
from the population-recruited hypertensives in having less opportunity
to practice the siesta.
This caveat may be circumvented by applying corresponding 24-hour
ambulatory blood pressure values instead of daytime values. Another
option is reporting actual awake blood pressure values from patients'
activity diaries instead of the average daytime values, which may
include those recorded during the siesta, as was done in other
studies.2 3 4 5 6 7 8 Either of these options will
eliminate the powerful effects of the siesta on daytime ambulatory
blood pressure.
References
1.
Palatini P, Mosmino P, Sandosantaso M, Mos L, Dal
Fallo M, Zanata G, Pessina AC. Target organ damage in stage I
hypertensive subjects with white coat and sustained hypertension:
results from the HARVEST Study. Hypertension.
1998;31(pt 1):57–63.
2.
Bursztyn M, Mekler J, Wachtel N, Ben-Ishay D. The
siesta and ambulatory blood pressure monitoring: comparability of the
afternoon nap and night sleep. Am J Hypertens. 1994;7:217–221.[Medline]
[Order article via Infotrieve]
3.
Bursztyn M, Mekler J, Ben-Ishay D. The siesta and
ambulatory blood pressure: is waking up the same in the morning and
afternoon? J Hum Hypertens. 1996;10:287–292.[Medline]
[Order article via Infotrieve]
4.
Bursztyn M, Mekler J, Ben-Ishay D. The siesta and
ambulatory blood pressure in hypertensive diabetics: attenuated decline
during day and nighttime sleep. J Hypertens.
1996;14(suppl 1):S184. Abstract.
5.
Mulcahy D, Wright C, Sparrow J, Cunningham D, Curcher
D, Purcell H, Fox K. Heart rate and blood pressure consequences of an
afternoon siesta (Snooze Induced Excitation of Sympathetic Triggered
Activity). Am J Cardiol. 1993;71:611–614.[Medline]
[Order article via Infotrieve]
6.
Stergiou GS, Malakos JS, Zourbaki AS, Achimastos AD,
Mountokalakis TD. Blood pressure during the siesta: effect on 24-h
ambulatory blood pressure analysis. J Hum Hypertens. 1997;11:125–131.[Medline]
[Order article via Infotrieve]
7.
Piexoto-Filho AJ, Mansoor GA, White WB. Effects of
actual versus arbitrary awake sleep times on analysis of
24-hour blood pressure. Am J Hypertens. 1995;8:676–680.[Medline]
[Order article via Infotrieve]
8.
Pickering TG. How should the diurnal change of blood
pressure be expressed? Am J Hypertens. 1995;8:681–682.[Medline]
[Order article via Infotrieve]
Response
Paolo Palatini;
; Paolo Mormino
Department of Clinical and Experimental Medicine,
University of Padova,
Padova, Italy
In response to the letter from Dr Bursztyn regarding the
possible influence of afternoon sleep on the calculation of daytime
blood pressure, the following data and comments are relevant.
The presence of an afternoon dip during 24-hour blood pressure
monitoring, not necessarily related to the siesta, has been found in
several countries, even outside the Mediterranean area or Latin
America.1 2 3 In an analysis of a large
database contributed by several countries, a profound afternoon dip was
found in persons from Australia and China, and a less pronounced one in
persons from France and Italy.1 No afternoon
blood pressure decline was found in subjects studied in Belgium,
Germany, Ireland, Japan, Sweden, and the United States. However, it has
to be pointed out that these data were not collected from random
population samples, and thus they are not truly
representative for each country. Moreover, they may be
influenced by the age and gender distributions of the study
participants.
As far as the HARVEST study participants are
concerned,4 it is worthwhile noting that they
live in a highly industrialized area (northeast Italy) that has the
lowest rate of unemployment for Italy (<5%). Persons living in this
region, especially the young, are no longer used to having a siesta, as
those in the southern part of Italy or other Mediterranean countries
still do. Thus, it is unlikely that the results we recently obtained in
a group of 18- to 45-year-old white coat hypertensive subjects are due
to the impact of an afternoon nap on the calculation of daytime blood
pressure.5
This conclusion is reinforced by a recent analysis of the
ambulatory blood pressure data in the HARVEST population.
Analysis of the hourly averages showed that the lowest
afternoon blood pressure values were reached from 1 PM to 4
PM in both the white coat hypertensive subjects (cutoff
point for daytime blood pressure, 130/80 mm Hg; n=150) and the
normotensive subjects (n=95). The average of the blood pressure
readings recorded during these 3 hours did not differ between the 2
groups, being 121.2±9.4/72.0±8.8 mm Hg in the white coat
hypertensive subjects and 120.9±11.9/71.8±7.8 mm Hg in the
normotensive subjects (P>0.8 for both systolic and
diastolic blood pressures). A modest decline in
diastolic blood pressure was observed during this time of
day in comparison with average daytime blood pressure calculated from
the remaining daytime hours (-1.4 mm Hg in white coat
hypertensive subjects and -2.8 mm Hg in normotensive subjects),
and there was virtually no change in systolic blood pressure
(+0.6 and +0.1 mm Hg, respectively). During the period of 1
PM to 4 PM, both diastolic and
systolic blood pressures were well above the values
recorded during nighttime (106.9±8.8/65.5±6.0 in white coat
hypertensive subjects and 105.7±10.1/63.6±8.2 in normotensive
subjects). Thus, even though we are unable to say how many of our study
participants, if any, had an afternoon sleep, it seems unlikely that
the prevalence of the siesta was unequally distributed between the
groups. Therefore, the low daytime blood pressure found in the HARVEST
study in the subjects with white coat hypertension cannot be ascribed
to a possible effect of an afternoon nap.
As for the possible impact of a different nighttime blood pressure on
the left ventricle of the normotensive and the white coat hypertensive
subjects, as suggested by Dr Burzstyn we also examined 24-hour blood
pressure and found no significant differences between the 2 groups.
Average 24-hour blood pressure was 117.9±6.5/72.3±4.9 mm Hg in
the white coat hypertensive subjects and 116.2±10.2/71.3±8.1
mm Hg in the normotensive subjects (NS).
The early afternoon is associated with a transient decline in alertness
in adults, a phenomenon that may cause a short-lasting slight decrease
in blood pressure in persons not taking a nap.6 A
greater afternoon fall in pressure is frequently detectable in elderly
subjects due to the effect of postprandial
hypotension.7 The siesta (postlunch sleep) is
less practiced in recent times than it used to be, especially in highly
developed countries where only a short pause from work, if any, is
taken after lunch. Today, the siesta is still practiced mostly in hot
countries,1 2 3 especially during the summer.
Certainly, this is not a common habit in the towns where the HARVEST
study is conducted, where summer temperature ranges from 17°C to
28°C.8
References
1.
Staessen J, O'Brien ET, Atkins N, Amery AK, for
the Ad Hoc Working Group. Short report: ambulatory blood pressure in
normotensive compared with hypertensive subjects. J
Hypertens. 1993;11:1289–1297.[Medline]
[Order article via Infotrieve]
2.
Bursztyn M, Mekler J, Wachtel N, Ben-Ishay D. The
siesta and ambulatory blood pressure monitoring. Am J
Hypertens. 1994;7:217–221.
3.
Stergiou GS, Malakos JS, Zourbaki AS, Achimastos AD,
Mountokalakis TD. Blood pressure during siesta: effect on 24-h
ambulatory blood pressure profiles analysis. J Hum
Hypertens. 1997;11:125–131.
4.
Palatini P, Pessina AC, Dal Palù C. Ambulatory
Recording Venetia Study (HARVEST): a trial on the predictive
value of ambulatory blood pressure monitoring for the development of
fixed hypertension in patients with borderline hypertension. High
Blood Pressure. 1993;2:11–18.
5.
Palatini P, Mormino P, Santonastaso M, Mos L, Dal
Follo M, Zanata G, Pessina AC. Target organ damage in stage I
hypertensive subjects with white coat and sustained hypertension:
results from the Harvest Study. Hypertension. 1998;31:57–63.[Abstract/Free Full Text]
6.
Mulcahy DM, Wright C, Sparrow J, Cunningham D, Curcher
D, Purcell H, Fox K. Heart rate and blood pressure consequences of an
afternoon siesta (Snooze-Induced Excitation of Sympathetic Triggered
Activity). Am J Cardiol. 1993;71:611–614.
7.
Lipsitz LA, Nyquist RP, Wei JY, Rowe JW. Postprandial
reduction in blood pressure in the elderly. N Engl J
Med. 1983;309:81–87.[Abstract]
8.
Winnicki M, Canali C, Accurso V, Dorigatti F,
Giovinazzo P, Palatini P. Relation of 24-hour ambulatory blood pressure
and short-term blood pressure variability to seasonal changes in
environmental temperature in stage I hypertensive subjects: results of
the HARVEST trial. Clin Exp Hypertens. 1996;18:995–1012.
