from the Ambulatory Blood Pressure in Referred Hypertensive

1There is longitudinal evidence that blood pressure (BP) recorded with ambulatory monitoring is more closely related to cardiovascular outcomes than clinic BP.1,2 Although the individual’s average values are considered of primary impor-tance in assessing risk of events, it is possible that other ambu-latory BP parameters might also be influential. Several studies have explored the association between ambulatory BP variabil-ity (BPV) and fatal or nonfatal cardiovascular events (CVE), but the extent to which knowledge of baseline BPV provides clini-cally meaningful risk information beyond mean ambulatory BP level and traditional risk factors in hypertension is unclear.3–13 In addition, it is not clear which ambulatory period is more predic-tive of future events. Daytime BPV is influenced by random BP fluctuations related to physical activities or occasional stress-ors that may occur during daily life. During sleep, BP is less affected by occasional triggers and high BPV may better reflect pathophysiological conditions such as baroreflex dysfunc-tion, arterial stiffness, or sleep apnea. Thus, we designed this study to investigate the contribution of ambulatory daytime and night-time BPVs to mean ambulatory BP and traditional risk factors in cardiovascular disease risk classification using dat