MORNING BLOOD PRESSURE SURGE POWER IS A BETTER PREDICTOR OF CARDIOVASCULAR DEATH OR EVENTS IN THE OHASAMA POPULATION THAN PRE-AWAKE VERSUS POST-AWAKE MEASURES

Abstract

Objective: The morning surge in blood pressure has been associated with increased cardiovascular risk. However, there has been no direct comparison to determine which method has the best prognostic value. The Ohasama study with 1522 participants, 126 cardiovascular deaths and 165 events was used to compare different methods of calculating the morning blood pressure surge (MBPS). Design and method: After adjustment for age, mean 24-hr mean BP, smoking, body mass index, sex and antihypertensive therapy, we calculated i) Cosinor curve amplitude ii) Day-night difference iii) MBPS 1 (2 hours Post-awake minus pre-awake) iv) MBPS 2 (2 hours post awake minus night minimum) v) morning rate of rise (RoR) and vii) morning surge power (rate x amplitude). The latter 2 are calculated using a logistic equation (Am Hypertens 2010;23:1074–1081). The outcome of combined cardiovascular events including death and non-fatal events were distributed into quintiles according to each MBPS measure and linear and quadratic trends determined as an indicator of a predictive ability. Results: Cosinor curve amplitude for between quintiles, linear and quadratic trends were P = 0.036,P = 0.122 and P = 0.257. Day-night difference for between quintiles, linear and quadratic trends were P = 0.113, P > 0.5 and P = 0.087. MBPS 1for between quintiles, linear and quadratic trends were P = 0.083, P > 0.5 and P = 0.074. MBPS 2 for between quintiles, linear and quadratic trends were P = 0.013, P = 0.34 and P = 0.068. Morning Power for between quintiles, linear and quadratic trends were P = 0.001, P = 0.244 and P = 0.035. MBPS1 and day night difference did not predict cardiovascular events. Cosinor amplitude and MBPS 2 showed differences between quintiles mainly due to high risk in the lowest quartile in which participants had little nocturnal dipping. By far the strongest predictor was morning BP power which showed a U-shaped relationship with combined cardiovascular events. We also observed a high correlation between adjusted morning power and MBPS1 (r = 0.50) and also with MBPS2 (r = 0.45) suggesting that these measures are reflecting some similar aspects of the morning surge. Conclusions: We conclude however, that the morning BP power is a superior and valuable predictive measure of cardiovascular risk even after adjustment for cofounders.