title: [Significant decline in blood pressure levels after 1996--fact or artefact?].
abstract: BACKGROUND
  Since 1985, the National Health Screening Service has regularly offered men and women aged 40-42 years in all Norwegian counties except Oslo a cardiovascular disease risk factor screening. After 1996, a substantial decline in blood pressure levels was observed.
  
  
  METHODS
  Data from eight counties which were screened both in 1994-96 and 1997-99.
  
  
  RESULTS
  Mean systolic/diastolic blood pressure was 135.3/81.1 and 129.2/75.7 mm Hg in men and 126.1/75.9 and 119.4/70.3 mm Hg in women. The change in blood pressure is considered in relation to methodological aspects, such as blood pressure devices, situation, whether the measurements have been taken in ambulatory buses or indoors, and also in relation to life-style and other factors linked to blood pressure.
  
  
  CONCLUSIONS
  No reasonable explanation for the blood pressure decline has been traced.
authors.affiliation: Forskningsavdelingen Statens helseundersøkelser Postboks 8155 Dep 0033 Oslo. aage.tverdal@shus.no
authors.forename: A
authors.initials: A
authors.lastname: Tverdal
mesh_terms: D000328:Adult; D018660:Blood Pressure Monitoring, Ambulatory / Q000379:methods / Q000639:trends; D003971:Diastole; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008403:Mass Screening; D009664:Norway / Q000453:epidemiology; D015995:Prevalence; D013599:Systole