title: Effect of different methods of accounting for antihypertensive treatment when assessing the relationship between diabetes or obesity and systolic blood pressure.
abstract: BACKGROUND
  Underlying blood pressure is that observed in the absence of antihypertensive treatment or, among those treated, the estimate of that which would be observed without treatment. This study aims to examine the relationships between diabetes or obesity and underlying systolic blood pressure adjusted for antihypertensive treatment by several methods.
  
  
  METHODS
  Data from two population studies were analyzed-an American Indian community in Arizona and the National Health and Nutrition Examination Surveys. Antihypertensive treatment was accounted for using: no adjustment; antihypertensive use as a covariate; blood pressure dichotomized into normotension and hypertension; addition of a fixed treatment effect; non-parametric algorithm; and censored normal regression.
  
  
  RESULTS
  The magnitude of association at each time point differed by adjustment method particularly where there was a difference in prevalence of antihypertensive use between people with and without diabetes or obesity. The common methods of ignoring antihypertensive treatment or including it as a covariate in a regression model underestimated the effects of diabetes and obesity on underlying blood pressure, compared to the recommended method of the censored normal regression.
  
  
  CONCLUSIONS
  Proper accounting for antihypertensive treatment is needed in interpreting variables that affect blood pressure.
authors.affiliation: National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, AZ. Electronic address: stephanie.tanamas@nih.gov.
authors.forename: Stephanie K
authors.initials: SK
authors.lastname: Tanamas
authors.affiliation: National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, AZ. Electronic address: rhanson@phx.niddk.nih.gov.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Hanson
authors.affiliation: National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, AZ. Electronic address: rnelson@phx.niddk.nih.gov.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Nelson
authors.affiliation: National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, AZ. Electronic address: wknowler@phx.niddk.nih.gov.
authors.forename: William C
authors.initials: WC
authors.lastname: Knowler
mesh_terms: D000328:Adult; D000368:Aged; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001130:Arizona / Q000453:epidemiology; D001794:Blood Pressure / Q000187:drug effects; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D048909:Diabetes Complications / Q000208:ethnology; D003925:Diabetic Angiopathies / Q000150:complications / Q000188:drug therapy* / Q000453:epidemiology / Q000208:ethnology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000188:drug therapy* / Q000453:epidemiology / Q000208:ethnology; D007198:Indians, North American; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D054525:Minority Health; D015233:Models, Statistical; D009749:Nutrition Surveys; D009765:Obesity / Q000150:complications* / Q000208:ethnology; D012307:Risk Factors; D012737:Sex Factors; D014481:United States / Q000453:epidemiology
chemical_list: D000959:Antihypertensive Agents
keywords: Antihypertensive treatment; Blood pressure; Diabetes; Obesity; Treatment effect