title: Twenty-four hour ambulatory blood pressure in the population.
abstract: OBJECTIVE
  To establish a population-based 24-h ambulatory blood pressure (ABP) reference material with day/night mean BP calculated by standardized and true bedtimes.
  
  
  METHODS
  A cross-sectional study of 200 randomly selected subjects (20 men and 20 women in each 10-year age interval 20-70 years) in Linköping, Sweden.
  
  
  METHODS
  University Hospital of Linköping, Sweden.
  
  
  RESULTS
  Participation rate was 67%. Mean supine clinic BP (CBP) and 24-h-ABP values for the whole material were 123 +/- 13/79 +/- 8 mmHg and 120 +/- 10/73 +/- 7 mmHg, respectively. White coat BP phenomenon increased with age (systolic CBP/ABP ratio versus age, r = 0.35, P < 0.0001). Seventeen participants had a night/day mean arterial blood pressure ratio > 0.9 (non-dipper) when calculated from their own time-notations. If standardized day (06.00-23.00) and night (23.00-06.00) limits were used, 24 subjects were non-dippers. Of these, only eight were 'true'. 'True' non-dippers had a similar day-time mean arterial ABP as 'true' dippers (92.4 +/- 11 mmHg versus 91.9 +/- 13 mmHg, P = 0.92) while night-time BP was higher (89.9 +/- 13 mmHg versus 74.1 +/- 7 mmHg, P < 0.0001).
  
  
  CONCLUSIONS
  Population-based ABP reference values have been defined. We found 9% non-dippers and that standardized day/night-time limits may lead to misclassification. This could be due to gender- and age-differences in sleeping habits, which was also shown in this study. The frequency of white coat BP phenomenon increases with age.
authors.affiliation: Department of Endocrinology, Faculty of Health Sciences, University Hospital, Linköping, Sweden.
authors.forename: F
authors.initials: F
authors.lastname: Nyström
authors.forename: O
authors.initials: O
authors.lastname: Malmström
authors.forename: B E
authors.initials: BE
authors.lastname: Karlberg
authors.forename: K P
authors.initials: KP
authors.lastname: Ohman
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D000553:Ambulatory Care; D001795:Blood Pressure Determination / Q000379:methods*; D002940:Circadian Rhythm; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012044:Regression Analysis; D012727:Sex Characteristics