Night and Day
What Blood Pressure Matters?
There is ample evidence that ambulatory blood pressure is significantly correlated with long-term prognosis. Such prognostic value holds true even after adjustment for the traditional risk factors and, more importantly, for office blood pressure.1 Therefore, ambulatory blood pressure monitoring is very useful when facing the decision to start treatment in hypertensive patients and to perform adequate follow-up. However, even with all of the technical improvements, 24-hour recordings are not always accepted well by the patients, because it may disturb both their daytime activities and sleep quality.
A logical question arising in this respect is to what extent we need the full 24-hour recordings to assess such prognostic information. Are there periods in the 24 hours that carry a heavier weight in prognosis? In particular, do we need nighttime recordings? These are considered by many patients as the most unpleasant part of the monitoring.
This has opened a controversy in the literature about the value of nighttime blood pressure, including the discussion around the significance of dipping versus nondipping patterns. One can find as many advocates in favor of the value of nighttime blood pressure and dipping2,3 as opponents.4 In the Office Versus Ambulatory Pressure Study,1 systolic blood pressure at night significantly correlated with long-term prognosis, but the correlation was not stronger, even weaker, than that of daytime blood pressure. Reasons for such controversy may come from technical aspects but also largely from the definition of night blood pressure (preset clock time versus information coming from log books) and obviously also from the quality of sleep.
In the article by Ben-Dov et al,5 published in this issue of Hypertension, night blood pressure comes out as a strong predictor of total mortality; no data on cardiovascular mortality or morbidity are given. The study was performed on 3957 patients followed over a mean duration of 6.5 years, totalling 27 750 patient-years. Ben-Dov et al5 confirmed the superior prognostic value of 24-hour ambulatory blood pressure also after adjustment for clinic blood pressure; however, night blood pressure performed best. The novelty of this article is that sleeping periods during the day (“naps”) were included with the aid of logbooks enlarging the total sleeping time over 24 hours. Of course, this automatically opens the discussion on the quality of logbooks filled out by the patients. No matter, having such calculation of “total” sleep, the authors were able to reinforce the prognostic value of sleep blood pressure even after adjustment for office blood pressures and several risk factors. Interestingly, the article leads to a new concept wherein sleep no longer is considered as an exclusive part of the night but is expanding all the way over night and day. The sequence of night and day is perceived as a continuum of events similar to the “drive” of a tune in music; a nice example of such drive can be found in the song composed by Cole Porter, appropriately titled “Night and Day.”
What does this information mean for the management of hypertensive patients? The essential message clearly is that the better we are informed on all parts of the 24-hour blood pressure curve, the better we can estimate prognosis and adjust our management. This means monitoring during the whole 24-hour cycle, including “naps” and other activities. Measurements should be accurate using validated instruments. However, this is the ideal clinical situation; is this feasible in all of the patients all over the world?
We should keep in mind that even with all of the clinical and scientific work done over the many years by numerous clinicians and scientists, control of blood pressure remains far below what we could expect. When following the figure obtained over the years, it seems that we do not reach goal pressure any better today than 10 years ago.6 There are many reasons for this disappointing observation, such as signs and symptoms arising after treatment initiation that were lacking before, which obviously causes bad compliance; blood pressure still is not sufficiently or correctly measured in the population at large; and, worse, no follow-up to the observations is given. Ambulatory blood pressure monitoring can strongly improve on such information, but the technique is cumbersome, expensive, and not reimbursed in many parts of the world. Analysis of the different parts of the curve (eg, sleeping blood pressure) and picking out what part has more prognostic significance could enable us to record shorter segments, which probably is more acceptable to the patients. But, what part is preferable: day, night, sleeping during the day, or just shorter segments during day or night? In this respect, home blood pressure recordings may be an easier and cheaper alternative with measurements obtained over several days; however, nighttime blood pressure is not obtained with this technique, which is a pity in light of the data of Ben-Dov et al.5
We need to come to a compromise knowing that all parts of the blood pressure profile, including office pressure, can bring in important information.7 We should stop considering blood pressure at a specific time of day or night, as “the” blood pressure representative for a particular patient. Our real blood pressure includes all of the values over the 24-hour cycle; the challenge is how to best approach it.
It is not clear yet what the compromise could be, but it should be easy and cheap and applicable to a large population. One could imagine making short bits of recordings during the 24-hour cycle in all newly discovered hypertensive patients that would allow us to find out the relationship of office blood pressure to the rest of the daytime pressure, to eventually discover “masked” hypertension,8 or make the diagnosis of dipping or no dipping. Follow-up could be done by home blood pressure recordings unless nighttime pressure needs further evaluation.
Is blood pressure more difficult to control than blood cholesterol? It seems so, because, remarkably, cholesterol control is improving.9 Clearly, the population and insurance bodies are more sensitive to the cholesterol message, because the latter largely agree to reimburse cholesterol-lowering drugs.
Our community should be better aware of the lack of good blood pressure control. The first step in this direction is better blood pressure measurement. Ambulatory techniques, made easier and better adapted to what really is relevant for the future of the patients, can help in this respect. Authorities should be informed to help us reach this important goal.
The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association.
Clement DL, De Buyzere ML, De Bacquer DA, De Leeuw PW, Duprez DA, Fagard RH, Gheeraert PJ, Missault LH, Braun JJ, Six RO, Van Der Niepen P, O’Brien E, for the Office Versus Ambulatory Pressure Study Investigators. Prognostic value of ambulatory blood pressure recordings in patients with treated hypertension. N Engl J Med. 2003; 348: 2407–2415.
Dolan E, Stanton A, Thijs L, Hinedi K, Atkins N, McClory S, Den Hond E, McCormack P, Staessen J, O’Brien E. Superiority of ambulatory over clinic blood pressure measurement in predicting mortality: the Dublin Outcome Study Hypertension. 2005; 46: 156–161.
Ohkubo T, Hozawa A, Yamaguchi J, Kikuya M, Ohmori K, Michimata M, Matsubara M, Hashimoto J, Hoshi H, Araki T, Tsuji I, Satoh H, Hisamichi S, Imai Y. Prognostic significance of the nocturnal decline in blood pressure in individuals with and without high 24-h blood pressure: the Ohasama study. J Hypertens. 2002; 20: 2183–2189.
Hansen TW, Jeppesen J, Rasmussen S, Ibsen H, Torp-Pedersen C. Ambulatory blood pressure monitoring and risk of cardiovascular disease: a population based study. Am J Hypertens. 2006; 19: 243–250.
Ben-Dov IZ, Kark JD, Ben-Ishay D, Mekler J, Ben-Arie L, Bursztyn M. Predictors of all-cause mortality in clinical ambulatory monitoring: unique aspects of blood pressure during sleep. Hypertension. 2007; 49: 1235–1241.
Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL, Jones DW, Materson BJ, Oparil S, Wright JT, Roccella EJ, and the National High Blood Pressure Education Program Coordinating Committee. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension. 2003; 42: 1206–1252.
Mancia G, Facchetti R, Bombelli M, Grassi G, Sega R. Long-term risk of mortality, associated with selective and combined elevation in office, home, and ambulatory blood pressure. Hypertension. 2006; 47: 1–8.
Pickering TG, Davidson K, Gerin W, Schwartz JE. Masked hypertension. Hypertension. 2002; 40: 795–798.
Pyorala K, Lehto S, De Bacquer D, De Sutter J, Sans S, Keil U, Wood D, De Backer G. EUROASPIRE I Group; EUROASPIRE II group. Risk factor management in diabetic and non-diabetic patients with coronary heart disease. Findings from the EUROASPIRE I and II surveys. Diabetologia. 2004; 47: 1257–1265.