title: Is Isolated Nocturnal Hypertension A Reproducible Phenotype?
abstract: BACKGROUND
  Isolated nocturnal hypertension (INH), defined as nocturnal without daytime hypertension on ambulatory blood pressure (BP) monitoring (ABPM), has been observed to be associated with an increased risk of cardiovascular disease (CVD) events and mortality. The aim of this study was to determine the short-term reproducibility of INH.
  
  
  METHODS
  The Improving the Detection of Hypertension Study enrolled a community-based sample of adults (N = 282) in upper Manhattan without CVD, renal failure, or treated hypertension. Each participant completed two 24-hour ABPM recordings (ABPM1: first recording and ABPM2: second recording) with a mean ± SD time interval of 33 ± 17 days between recordings. Daytime hypertension was defined as mean awake systolic/diastolic BP ≥ 135/85 mm Hg; nocturnal hypertension as mean sleep systolic/diastolic BP ≥ 120/70 mm Hg; INH as nocturnal without daytime hypertension; isolated daytime hypertension (IDH) as daytime without nocturnal hypertension; day and night hypertension (DNH) as daytime and nocturnal hypertension, and any ambulatory hypertension as having daytime and/or nocturnal hypertension.
  
  
  RESULTS
  On ABPM1, 26 (9.2%), 21 (7.4%), and 50 (17.7%) participants had INH, IDH, and DNH, respectively. On ABPM2, 24 (8.5%), 19 (6.7%), and 54 (19.1%) had INH, IDH, and DNH, respectively. The kappa statistics were 0.21 (95% confidence interval (CI) 0.04-0.38), 0.25 (95% CI 0.06-0.44), and 0.65 (95% CI 0.53-0.77) for INH, IDH, and DNH respectively; and 0.72 (95% CI 0.63-0.81) for having any ambulatory hypertension.
  
  
  CONCLUSIONS
  Our results suggest that INH and IDH are poorly reproducible phenotypes, and that ABPM should be primarily used to identify individuals with daytime hypertension and/or nocturnal hypertension.
authors.affiliation: Department of Medicine, Columbia University Medical Center, New York, USA; ma2947@cumc.columbia.edu.
authors.forename: Marwah
authors.initials: M
authors.lastname: Abdalla
authors.affiliation: Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, USA;
authors.forename: Jeff
authors.initials: J
authors.lastname: Goldsmith
authors.affiliation: Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama, USA;
authors.forename: Paul
authors.initials: P
authors.lastname: Muntner
authors.affiliation: Department of Medicine, Columbia University Medical Center, New York, USA;
authors.forename: Keith M
authors.initials: KM
authors.lastname: Diaz
authors.affiliation: Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, California, USA;
authors.forename: Kristi
authors.initials: K
authors.lastname: Reynolds
authors.affiliation: Department of Medicine, Columbia University Medical Center, New York, USA; Applied Behavioral Medicine Research Institute, Stony Brook University, Stony Brook, New York, USA.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Schwartz
authors.affiliation: Department of Medicine, Columbia University Medical Center, New York, USA;
authors.forename: Daichi
authors.initials: D
authors.lastname: Shimbo
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory / Q000379:methods*; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D010641:Phenotype; D015203:Reproducibility of Results; D012890:Sleep / Q000502:physiology*
keywords: ambulatory blood pressure; isolated nocturnal hypertension; reproducibility.