title: The effect of race and sleep-disordered breathing on nocturnal BP "dipping": analysis in an older population.
abstract: OBJECTIVE
  BP normally drops (or "dips") by approximately 10% at nighttime; however, in a number of illnesses there is an increased amount of "nondipping" of nocturnal BP. This study examined whether nondipping in older African Americans and older white subjects is related to the presence of sleep-disordered breathing (SDB) and hypertension.
  
  
  METHODS
  Prospective study with a convenience sample.
  
  
  METHODS
  All data were collected in the subjects' homes.
  
  
  METHODS
  Seventy self-defined African Americans with complaints of snoring or excessive daytime sleepiness, and 70 age-matched and gender-matched white subjects.
  
  
  RESULTS
  Sleep was recorded for 2 nights, with 1 night of oximetry. BP was recorded on a separate 24-h period. African Americans had higher dipping ratios than white subjects even after accounting for covariates such as respiratory disturbance index (RDI), oxygen desaturation index (ODI), body mass index, and average 24-h mean arterial pressure (p = 0.025). Higher values of RDI (R(2) = 0.0686, p = 0.021) and ODI (R(2) = 0.042, p < 0.03) were correlated with higher dipping ratios in both African Americans and white subjects. However, there was a three-way interaction such that higher RDIs were correlated primarily with nondipping in African Americans receiving antihypertensive medication (R(2) = 0.0373, p = 0.022).
  
  
  CONCLUSIONS
  These results demonstrated that African Americans tend to be "nondippers," while white subjects tended to be "dippers." This nondipping was not a result of weight, gender, or of having SDB. The analyses also confirmed that, in both races, the dipping ratio was greatest in those with SDB and hypertension. The third hypothesis, that RDI would be greatest in the nondipping hypertensive subjects, was true only for the African Americans.
authors.affiliation: Department of Psychiatry, University of California, San Diego, CA, USA. sancoliisrael@ucsd.edu
authors.forename: Sonia
authors.initials: S
authors.lastname: Ancoli-Israel
authors.forename: Carl
authors.initials: C
authors.lastname: Stepnowsky
authors.forename: Joel
authors.initials: J
authors.lastname: Dimsdale
authors.forename: Matthew
authors.initials: M
authors.lastname: Marler
authors.forename: Mairav
authors.initials: M
authors.lastname: Cohen-Zion
authors.forename: Sherella
authors.initials: S
authors.lastname: Johnson
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D044383:Black People; D001795:Blood Pressure Determination; D015992:Body Mass Index; D016022:Case-Control Studies; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000175:diagnosis / Q000208:ethnology*; D007022:Hypotension / Q000208:ethnology*; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D012016:Reference Values; D018570:Risk Assessment; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D012891:Sleep Apnea Syndromes / Q000150:complications / Q000175:diagnosis / Q000208:ethnology*; D044465:White People; D001741:Black or African American