Nondipping in Patients With Hypertension
To the Editor:
de la Sierra et al1 provide further information from the largest accessible ambulatory blood pressure monitoring data set. In a recent issue of Hypertension, these authors, on behalf of the Spanish Society of Hypertension Ambulatory Blood Pressure Monitoring Registry Investigators, compared the clinical characteristics of ≈43 000 hypertensive patients with (49.5%) and without (50.5%) normal blood pressure dipping. Their findings confirmed and strengthened associations reported previously, such as an increased nondipping rate among subjects with diabetes mellitus and the elderly.2 The findings of the Spanish study are of major support not only because of the large patient population but also because they demonstrate sound clinical associations with the circadian blood pressure pattern regardless of whether the subjects examined were treated or untreated and regardless of whether the mode of examination involved dipping as a categorical or as a continuous phenomenon. These strengths, unlikely to be replicated in future studies, should enable examination of suggestions hypothesized previously by smaller-scaled studies. Thus, we would appreciate the authors’ comments on several issues that evolve from their report. First, although normal dipping is defined as ≥10% nocturnal reduction in systolic blood pressure, >50% of the monitored patients had a lesser decline. Could this high rate of nondipping result from a high prevalence of daytime napping (siesta), with measurements made during these periods included in the daytime average? Second, could the timing of antihypertensive medication dosing relate to nondipping in a manner opposite to that suggested by previous trials?3 In univariable analyses, the authors showed a weak, but significant, relationship between nighttime administration of medications and decreased sleep-related dipping, whereas in multivariable models this parameter was absent. Third, the authors stated that specific classes of antihypertensive agents did not significantly affect the variables associated with nocturnal blood pressure decline. However, a direct examination of links between specific drugs and the magnitude of dipping was not reported. Previous studies suggested that dipping might be positively associated with diuretics4 and negatively linked with α-adrenergic blockers.5 Data from the Spanish registry may shed invaluable light on this issue.
de la Sierra A, Redon J, Banegas JR, Segura J, Parati G, Gorostidi M, de la Cruz JJ, Sobrino J, Llisterri JL, Alonso J, Vinyoles E, Pallares V, Sarría A, Aranda P, Ruilope LM, on behalf of the Spanish Society of Hypertension Ambulatory Blood Pressure Monitoring Registry Investigators. Prevalence and factors associated with circadian blood pressure patterns in hypertensive patients. Hypertension. 2009; 53: 466–472.
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.
Hermida RC, Ayala DE, Fernandez JR, Calvo C. Chronotherapy improves blood pressure control and reverts the nondipper pattern in patients with resistant hypertension. Hypertension. 2008; 51: 69–76.
Uzu T, Kimura G. Diuretics shift circadian rhythm of blood pressure from nondipper to dipper in essential hypertension. Circulation. 1999; 100: 1635–1638.