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.
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.
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.
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.
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.
Pickering TG. How should the diurnal change of blood pressure be expressed? Am J Hypertens. 1995;8:681–682.
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.R1 R2 R3 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.R1 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,R4 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.R5
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.R6 A greater afternoon fall in pressure is frequently detectable in elderly subjects due to the effect of postprandial hypotension.R7 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,R1 R2 R3 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.R8
Bursztyn M, Mekler J, Wachtel N, Ben-Ishay D. The siesta and ambulatory blood pressure monitoring. Am J Hypertens. 1994;7:217–221.
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.
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.
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.
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.
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.