Response to Timing of Antihypertensive Therapy and Circadian Blood Pressure Pattern
We thank Almirall et al1 for their interest in our article.2 In the present answer to their letter, we provide data from the Spanish Ambulatory Blood Pressure Monitoring Registry regarding clinical differences among patients depending on the time that they received their medication (Table). As shown, several differences were evident among groups, with respect to age, duration of hypertension, prevalence of diabetes mellitus, and history of previous cardiovascular disease, with all of these factors being more prevalent in patients receiving all or part of their medication at night. The same groups also had higher values of 24-hour, daytime, and nighttime systolic blood pressures, although night: day ratio was only increased in those who received medication both in the morning and at bedtime. As we suggested in our main article,2 the timing of antihypertensive treatment had no great influence on the magnitude of dipping and other variables influencing risk (eg, age, diabetes mellitus, previous cardiovascular events, or blood pressure itself); they all seemed to have influence on both the amount of dipping and also on the time that the medication was given to the patient. A blunted dipping because of low daytime blood pressure as a consequence of more advance cardiovascular disease has also been suggested by another prospective database.3 This does not necessarily reject the previous hypothesis raised in controlled clinical trials regarding a reversal of the nondipping pattern by switching treatment from the morning to bedtime.4 The Spanish Ambulatory Blood Pressure Monitoring Registry1 is a cross-sectional epidemiological survey, and no inference on causality is allowed. As Almirall et al1 clearly pointed out in their letter, the impact of chronotherapy, not merely on the circadian pattern, but also on the cardiovascular outcome, is still an open question and needs to be answered in a prospective, controlled clinical trial.
Sources of Funding
The Spanish Ambulatory Blood Pressure Monitoring Registry has been funded through an unrestricted grant from Lacer Laboratories, Spain.
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