Original papers: Blood pressure measurementA new method for assessing 24-h blood pressure variability after excluding the contribution of nocturnal blood pressure fallBilo, Grzegorza,b,c; Giglio, Alessiab; Styczkiewicz, Katarzynab,c; Caldara, Gianlucab; Maronati, Albertob; Kawecka-Jaszcz, Kalinac; Mancia, Giuseppea,b; Parati, Gianfrancoa,bAuthor Information aDepartment of Clinical Medicine and Prevention, University of Milano-Bicocca, Italy bDepartment of Cardiology, S. Luca Hospital, IRCCS, Istituto Auxologico Italiano, Milan, Italy cI Department of Cardiology and Hypertension, Jagiellonian University Medical College, Krakow, Poland Received 15 November, 2006 Revised 19 May, 2007 Accepted 28 May, 2007 Correspondence to Gianfranco Parati, MD, Istituto Scientifico Ospedale San Luca, Istituto Auxologico Italiano, via Spagnoletto 3, 20149 - Milan, Italy Tel: +39 02 619112980; fax: +39 02 619112956; e-mail: email@example.com Some of these data were included in the proceedings of a workshop held during the 2004 European Society of Hypertension Meeting (Bilo G et al. How to improve the assessment of 24-h blood pressure variability. Blood Pressure Monitoring 2005; 10:321–323.) Journal of Hypertension: October 2007 - Volume 25 - Issue 10 - p 2058-2066 doi: 10.1097/HJH.0b013e32829c6a60 Buy Metrics Abstract Objectives To assess quantitatively the relationship between nocturnal blood pressure (BP) fall and 24-h BP variability; to propose a new method for computing 24-h BP variability, devoid of the contribution from nocturnal BP fall; and to verify the clinical value of this method. Methods and results We analysed 3863 ambulatory BP recordings, and computed: (1) the standard deviation (SD) of 24-h BP directly from all individual readings and as a weighted mean of daytime and night-time SD (wSD); and (2) the size of nocturnal BP fall. Left ventricular mass index (LVMI) was assessed by echocardiography in 339 of the patients. The 24-h SD of BP was significantly greater than the 24-h wSD. Nocturnal BP fall was strongly and directly related to 24-h SD, the relationship with 24-h wSD being much weaker and inverse. The difference between SD and wSD was almost exclusively determined by the size of nocturnal BP fall. wSD of systolic BP was significantly related to LVMI, while 24-h SD was not. Conclusion Conventional 24-h SD of BP is markedly influenced by nocturnal BP fall. The weighted 24-h SD of BP removes the mathematical interference from night-time BP fall and correlates better with end-organ damage, therefore it may be considered as a simple index of 24-h BP variability superior to conventional 24-h SD. © 2007 Lippincott Williams & Wilkins, Inc.