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Original Investigation
August 14, 2019

Association of Daytime and Nighttime Blood Pressure With Cardiovascular Disease Events Among African American Individuals

Author Affiliations
  • 1Department of Family Medicine and Community Health, Duke University, Durham, North Carolina
  • 2Department of Epidemiology, University of Alabama at Birmingham, Birmingham
  • 3Department of Biostatistics, University of Alabama at Birmingham, Birmingham
  • 4Department of Medicine, Columbia University, New York, New York
  • 5Department of Mathematics and Statistics, University of West Florida, Pensacola
  • 6Department of Population Health, New York University School of Medicine, New York
  • 7Mississippi Center for Obesity Research, University of Mississippi Medical Center, Jackson
JAMA Cardiol. Published online August 14, 2019. doi:10.1001/jamacardio.2019.2845
Key Points

Question  Among African American individuals, are daytime and nighttime blood pressure levels measured outside the clinic associated with cardiovascular disease independent of blood pressure levels measured inside the clinic?

Findings  In this cohort study of 1034 African American individuals, higher daytime and nighttime systolic blood pressures were associated with an increased risk for cardiovascular disease events independent of blood pressure levels measured in the clinic.

Meaning  Measurement of daytime and nighttime blood pressure using ambulatory monitoring during a 24-hour period may help identify African American individuals who have an increased cardiovascular disease risk.

Abstract

Importance  Little is known regarding health outcomes associated with higher blood pressure (BP) levels measured outside the clinic among African American individuals.

Objective  To examine whether daytime and nighttime BP levels measured outside the clinic among African American individuals are associated with cardiovascular disease (CVD) and all-cause mortality independent of BP levels measured inside the clinic.

Design, Setting, and Participants  This prospective cohort study analyzed data from 1034 African American participants in the Jackson Heart Study who completed ambulatory BP monitoring at baseline (September 26, 2000, to March 31, 2004). Mean daytime and nighttime BPs were calculated based on measurements taken while participants were awake and asleep, respectively. Data were analyzed from July 1, 2017, to April 30, 2019.

Main Outcomes and Measures  Cardiovascular disease events, including coronary heart disease and stroke, experienced through December 31, 2014, and all-cause mortality experienced through December 31, 2016, were adjudicated. The associations of daytime BP and nighttime BP, separately, with CVD events and all-cause mortality were determined using Cox proportional hazards regression models.

Results  A total of 1034 participants (mean [SD] age, 58.9 [10.9] years; 337 [32.6%] male; and 583 [56.4%] taking antihypertensive medication) were included in the study. The mean daytime systolic BP (SBP)/diastolic BP (DBP) was 129.4/77.6 mm Hg, and the mean nighttime SBP/DBP was 121.3/68.4 mm Hg. During follow-up (median [interquartile range], 12.5 [11.1-13.6] years for CVD and 14.8 [13.7-15.6] years for all-cause mortality), 113 CVD events and 194 deaths occurred. After multivariable adjustment, including in-clinic SBP and DBP, the hazard ratios (HRs) for CVD events for each SD higher level were 1.53 (95% CI, 1.24-1.88) for daytime SBP (per 13.5 mm Hg), 1.48 (95% CI, 1.22-1.80) for nighttime SBP (per 15.5 mm Hg), 1.25 (95% CI, 1.02-1.51) for daytime DBP (per 9.3 mm Hg), and 1.30 (95% CI, 1.06-1.59) for nighttime DBP (per 9.5 mm Hg). Nighttime SBP was associated with all-cause mortality (HR per 1-SD higher level, 1.24; 95% CI, 1.06-1.45), but no association was present for daytime SBP (HR, 1.13; 95% CI, 0.97-1.33) and daytime (HR, 0.95; 95% CI, 0.81-1.10) and nighttime (HR, 1.06; 95% CI, 0.90-1.24) DBP.

Conclusions and Relevance  Among African American individuals, higher daytime and nighttime SBPs were associated with an increased risk for CVD events and all-cause mortality independent of BP levels measured in the clinic. Measurement of daytime and nighttime BP using ambulatory monitoring during a 24-hour period may help identify African American individuals who have an increased cardiovascular disease risk.

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