Is the definition of daytime and nighttime blood pressure prognostically relevant?

Abstract

OBJECTIVES: Although the prognostic value of the day-night blood pressure (BP) changes is well established, the most appropriate method for definition of daytime and nighttime BP is still undefined. In a recent guidelines document of the European Society of Hypertension, there is no clear position in favor of one definition over other. METHODS: In the setting of the Progetto Ipertensione Umbria Monitoraggio Ambulariale study, we analyzed the prognostic impact of the day-night BP changes by using three widely used different definitions of day and night (large fixed-clock intervals, narrow fixed-clock intervals, diary) in 2934 initially untreated participants with essential hypertension. RESULTS: Three hundred and fifty-six cardiovascular events and 176 deaths over a median follow-up period of 7 years were observed. Nondippers showed a higher risk of total cardiovascular events and all-cause mortality than dippers regardless of the definition of day and night. Furthermore, the area under a receiver-operated characteristic curve analysis did not differ among the different definitions of day and night (large fixed-clock intervals, narrow fixed-clock intervals, diary) for total cardiovascular events and all-cause mortality (all P=NS). CONCLUSION: The data suggest that the prognostic value of the diurnal BP changes is comparable when day and night are defined using large fixed-clock intervals, narrow fixed-clock intervals, or actual time spent in and out of bed.