Objective: To review the literature to examine critically the assertion that night-time blood pressure is a better predictor of echocardiographic left ventricular mass than daytime blood pressure, and that left ventricular mass is inversely related to the day-night blood pressure difference.
Study selection: Published studies in which left ventricular mass (index) of normotensive or hypertensive individuals, or both, was related to automated blood pressure measurement during the day and night, or their difference, or both.
Results of data analysis: The meta-analysis of 19 comparative studies, involving 1223 participants, indicates that the weighted correlation coefficient for the relationship between left ventricular mass (index) and systolic night-time blood pressure (0.44; 95% confidence limit 0.39-0.48) is not significantly different from the correlation with systolic daytime blood pressure (0.48; 95% confidence limit 0.44-0.52; P > 0.2). The corresponding correlation coefficients for diastolic blood pressure both average 0.37. In half of the eight studies in which the association between left ventricular mass (index) and the day-night difference in blood pressure was analysed, investigators found no significant relationship between those variables; in the others, the variance of the mass (index) that can be explained by the blood pressure difference is 15% at the most.
Conclusion: The overall analysis suggests that night-time blood pressure is not a significantly better predictor of left ventricular mass than daytime blood pressure is, and that the relationship to the day-night blood pressure difference is not a unanimous finding and is only ever weakly significant.