Soolim Jeong, Braxton A. Linder, McKenna A. Tharpe, Zach J. Hutchison, Meral N. Culver, Olivia I. Nichols, Thomas E. Fuller-Rowell, Austin T. Robinson. Auburn University, Auburn, AL.

BACKGROUND: Night-to-day blood pressure (BP) ratio and BP dipping pattern are prognostic of future cardiovascular events and morbidities. Prior studies have demonstrated racial disparities in night-to-day BP ratio and BP dipping in middle-aged and older adults, but when these disparities emerge remains unclear. Therefore, the purpose of this investigation was to determine whether racial disparities in night-to-day BP ratio and BP dipping exist in healthy young adults using ambulatory blood pressure monitoring (ABPM). METHODS: 41 adults (19M/22F) including 16 Black (age 21.4±0.6 yrs, BMI 25.4±4.3 kg/m2, screening BP 108±10/66±10 mmHg; Mean±SD) and 25 White (age 21.2±0.7 yrs, BMI 25.2±3.8 kg/m2, screening BP 106±9/62±7 mmHg) adults participated in this study. For ABPM (Suntech Oscar2), participants wore a 24-hour brachial cuff on their upper left arm which measured BP every 20 minutes during awake hours and every 30 minutes during sleep hours (self-reported). We defined daytime as 1000 to 2000 and nighttime as 0000 to 0600. Participants with at least 20 daytime and 7 nighttime readings (n=41) were included in the analysis. Primary outcomes included night-to-day BP ratio (nighttime/daytime BP) and nocturnal BP dipping (awake-asleep mmHg). We instructed participants to wear a waist-worn accelerometer (ActiGraph GT3X-BT) for seven days to assess moderate-vigorous physical activity (MVPA) and step count to account for ABPM differences due to physical activity. Statistical procedures included multivariate analysis of variance with Hotelling’s trace, and Pearson’s correlation (a priori α<0.05). RESULTS: Significant racial differences (Black vs White) existed for night-to-day BP ratios whereby Black participants had a higher brachial systolic BP ratio (0.92±0.06 vs 0.86±0.05, p<0.001), diastolic BP ratio (0.87±0.08 vs 0.78±0.10, p=0.002), central systolic BP ratio (p=0.003), and central diastolic BP ratio (p=0.002). Racial differences also existed for BP dipping whereby Black participants had a lower nighttime brachial systolic BP dip (7±6 vs 11±5 mmHg, p=0.008) and diastolic BP dip (11±8 mmHg vs 18±8 mmHg, p=0.017). Daily time spent in MVPA (7.5±3.0%) and steps (6581±3652) were not correlated with ABPM primary outcomes nor different between racial groups (p>0.05 for all). CONCLUSIONS: These preliminary findings suggest a racial disparity in night-to-day BP ratio and BP dipping in healthy young adults.

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