title: Establishing the prevalence of hypertension. Influence of sampling criteria.
abstract: OBJECTIVE
  To compare the prevalence of systemic hypertension in two different populations: a representative sample of the adult urban population of Porto Alegre, and individuals who sought blood pressure measurement in a hypertension prevention and control campaign.
  
  
  METHODS
  A cross-sectional study was carried out involving a representative sample of the adult urban population of Porto Alegre and a population sample obtained from a hypertension prevention and control campaign, which included all the individuals who sought the blood pressure assessment unit at the Hospital das Clínicas in Porto Alegre. The following parameters were investigated: history of hypertension, use of antihypertensive drugs, age, and sex. Adjustments for age and sex in the prevalence rates were performed to make them comparable.
  
  
  RESULTS
  Hypertension prevalence, defined as values > or =160/95 mmHg or treatment with antihypertensive drugs, was higher in the campaign sample (42%) as compared with the population sample (24%). Among those who were aware of their hypertensive condition and were under medication, 54% of the campaign sample and 62% of the representative population sample maintained their pressure levels <160/90 mmHg.
  
  
  CONCLUSIONS
  Prevalence rates of hypertension differed a lot in the campaign sample and in the representative population sample, showing that the sampling criterion may influence assessment of risk factors and bias the association between risk factors and health aggravations.
authors.affiliation: Hospital de Clínicas de Porto Alegre, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: S C
authors.initials: SC
authors.lastname: Fuchs
authors.forename: J G
authors.initials: JG
authors.lastname: Petter
authors.forename: M C
authors.initials: MC
authors.lastname: Accordi
authors.forename: V L
authors.initials: VL
authors.lastname: Zen
authors.forename: A D
authors.initials: AD
authors.lastname: Pizzol
authors.forename: L B
authors.initials: LB
authors.lastname: Moreira
authors.forename: F D
authors.initials: FD
authors.lastname: Fuchs
mesh_terms: D000293:Adolescent; D000328:Adult; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000453:epidemiology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012494:Sampling Studies; D014505:Urban Population