International Journal of Cardiology 87 (2003) 9–28 www.elsevier.com / locate / ijcard C ircadian heart rate and blood pressure variability considered for resear and patient care a , b c b b * ´ Ram B.Singh , Germaine Cornelissen , AndiWeydahl , Othild Schwartzkopff , George Katinas , b d e f g KuniakiOtsuka , Yoshihiko Watanabe , ShokiYano ,HidekiMori , Yuhei Ichimaru , h i j j a k Gen Mitsutake , DanielPella ,Lu Fanghong , Ziyan Zhao , Reema S. Rao ,Anna Gvozdjakova , b Franz Halberg a Medical Hospital and Research Center , CivilLines , Moradabad 10 ( UP), 244001 India b Halberg Chronobiology Center , University of Minnesota , Minneapolis , MN , USA c Finnmark College , Alta , Norway d Tokyo Women ’ s Medical University , Tokyo , Japan e Hokkaido Institute of Public Health , Sapporo , Japan f AmoriPrefectural Central Hospital , Amori , Japan g Schoolof Home Economics and Science , Tokyo , Japan h University of Manitoba , Winnipeg , Manitoba , Canada i 2 nd Internal Clinic , PJ Safarik University , Kosice , Slovakia j Institute of Materia Medica , Shandong , China k Pharmacobiochemical Laboratory , Bratislava , Slovakia Received 3 April 2001;received in revised form 25 January 2002; accepted 25 March 2002 Abstract Objectives : To review mechanisms of circadian variations in heart rate variability (HRV) and blood pressure variability (BPV) and mortality and morbidity due to cardiovascular diseases (CVD). Methods : Results from 7-day / 24-h HRV and BPV are interpreted by gender and age-specified reference values in the context of a Medline search. Results : Abnormal HRV and BPV measured around the clock for 7 days provides information on the risk of subsequent morbid events in subjects without obvious heart disease and without abnormality outside the conventional (in the sense of chronobiologically unquantified) physiological range. Meditation, b-blo inhibitors, n-3 fatty acids and estrogens may have a beneficial influence on HRV, butthere is no definitive outcome-validated therapy. Low HRV has been associated with a risk of arrhythmias and arrhythmic death, unstable angina, myocardial infarction, progression of heartfailure and atherosclerosis. BPV may be characterized by treatable circadian-hyper-amplitude-tension (CHAT), which can be transient ‘24-h CHAT’or ‘7-day-CHAT’, MESOR-hypertension and / or an unusually-timed (odd) circadian acrophase (ecphasia), all associated with an increased risk of stroke, stroke death, myocardial infarction, and kidney disease. Conclusions : Precise insight into the patho-physiology in time of HRV and BPV is needed with development of a consensus on best measures of HRV for clinical p to determine when a 7-day record interpreted chronobiologically suffices and when it does not, for detection within as well conventional normal range, for diagnostic clinical practice and to direct therapy of risk greater than that associated with hypertension, smoking or any other risk factor.  2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords : Heartrate variability; Blood pressure variability; Circadian variation; Sudden death *Corresponding author. Tel.: 191-591-417-437. E-mailaddress : icn@mickyonline.com (R.B. Singh). 0167-5273 / 02 / $ – see front matter  2002 Elsevier Science Ireland Ltd. All rights reserved. P I I : S 0 1 6 7 - 5 2 7 3 ( 0 2 ) 0 0 3 0 8 - X