Relations between white coat effects and left ventricular mass index or arterial stiffness: role of nocturnal blood pressure dipping.
BACKGROUND
Whether independent relationships between white coat effects (office minus day (office-day blood pressure (BP))) and organ damage or arterial stiffness may be explained by associations with an attenuated nocturnal BP dipping, has not been determined.


METHODS
In 750 participants from a sample of African ancestry, office and 24-hour BP, carotid-femoral pulse wave velocity (PWV) (applanation tonometry and SphygmoCor software) (n = 662), and left ventricular mass indexed to height(2.7) (LVMI) (echocardiography) (n = 463) were determined.


RESULTS
Office-day systolic BP (SBP) was correlated with day minus night (day-night) SBP, percentage night divided by day (night/day) SBP, and night SBP (P < 0.0005), and these relationships persisted with adjustments for confounders, including day SBP (P < 0.005). With adjustments for 24-hour SBP and additional confounders, office-day SBP was associated with LVMI (P < 0.01) and PWV (P < 0.0001). With adjustments for day SBP and additional confounders, day-night SBP, percentage night/day SBP, and night SBP were related to PWV (P < 0.05) but not to LVMI (P > 0.44). The relationships between office-day SBP and LVMI or PWV persisted with adjustments for either day-night or percentage night/day SBP (LVMI: P = 0.01; PWV: P < 0.0001) or night SBP (LVMI: P < 0.01; PWV: P = 0.0001), and in product of coefficient mediation analysis with appropriate adjustments, neither indexes of nocturnal BP dipping nor nocturnal BP per se contributed toward the impact of office-day BP on LVMI or PWV (P > 0.09).


CONCLUSIONS
In a group of African ancestry, although white coat effects are independently associated with an attenuated nocturnal decrease in SBP, neither decreased BP dipping nor nocturnal BP contribute toward the independent relationships between white coat effects and LVMI or arterial stiffness.
Cardiovascular Pathophysiology and Genomics Research Unit, School of Physiology, Faculty of Health Scienes, University of the Witwatersrand, Johannesburg, South Africa;
Muzi J
MJ
Maseko
Cardiovascular Pathophysiology and Genomics Research Unit, School of Physiology, Faculty of Health Scienes, University of the Witwatersrand, Johannesburg, South Africa; angela.woodiwiss@wits.ac.za.
Angela J
AJ
Woodiwiss
Cardiovascular Pathophysiology and Genomics Research Unit, School of Physiology, Faculty of Health Scienes, University of the Witwatersrand, Johannesburg, South Africa; School of Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
Carlos D
CD
Libhaber
Cardiovascular Pathophysiology and Genomics Research Unit, School of Physiology, Faculty of Health Scienes, University of the Witwatersrand, Johannesburg, South Africa;
Richard
R
Brooksbank
Cardiovascular Pathophysiology and Genomics Research Unit, School of Physiology, Faculty of Health Scienes, University of the Witwatersrand, Johannesburg, South Africa;
Olebogeng H I
OH
Majane
Cardiovascular Pathophysiology and Genomics Research Unit, School of Physiology, Faculty of Health Scienes, University of the Witwatersrand, Johannesburg, South Africa; angela.woodiwiss@wits.ac.za.
Gavin R
GR
Norton
D000328:Adult; D001794:Blood Pressure; D002940:Circadian Rhythm; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D063177:Pulse Wave Analysis; D014463:Ultrasonography; D059289:Vascular Stiffness; D059466:White Coat Hypertension / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*
blood pressure; hypertension; left ventricular mass index; nocturnal blood pressure dipping; pulse wave velocity; white coat effects.