title: Is blood pressure load associated, independently of blood pressure level, with target organ damage?
abstract: OBJECTIVE
  Blood pressure (BP) load, defined as the percentage of abnormally elevated BP readings, is usually provided on the report of ambulatory BP monitoring. However, the usefulness of BP load is still uncertain. In the present study, we examined whether BP load would be associated, independently of BP level, with target organ damage.
  
  
  METHODS
  We recruited 869 individuals (430 men, mean age 51 years) who were referred for 24-h ambulatory BP monitoring and were off antihypertensive medication for at least 2 weeks. BP load was defined as the percentage of daytime and nighttime SBP/DBP readings at least 135/85 and at least 120/70 mmHg, respectively. Brachial-ankle pulse wave velocity (baPWV) and carotid-femoral pulse wave velocity (cfPWV), left ventricular mass index (LVMI) and urinary albumin-to-creatinine ratio (ACR) were determined as measures of target organ damage.
  
  
  RESULTS
  SBP and DBP load had a skewed distribution (P<0.001). In multivariate-adjusted categorical analyses, baPWV (13.8, 14.6 and 15.6 m/s), cfPWV (7.4, 7.7 and 8.4 m/s), LVMI (90.1, 94.8 and 100.7 g/m) and ACR (0.47, 0.58 and 0.77 mg/mmol) all increased from tertiles 1-3 of SBP load (P<0.001). However, these differences became nonsignificant (P ≥ 0.16) after additionally adjusted for 24-h SBP level. In a continuous analysis in individuals with a BP load greater than zero (n=838), adding the logarithmically transformed SBP load did not improve the fit of models relating measures of target organ damage to SBP level (P ≥ 0.14), except for cfPWV (P=0.01) that was however negatively associated with BP load. Analyses on DBP load produced similar results.
  
  
  CONCLUSIONS
  BP load was associated with target organ damage, but not independently of BP level.
authors.affiliation: Centre for Vascular Evaluations and Centre for Epidemiological Studies and Clinical Trials, Shanghai Key Laboratory of Hypertension, The Shanghai Institute of Hypertension, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Liu
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Fang-Fei
authors.initials: FF
authors.lastname: Wei
authors.forename: Lu
authors.initials: L
authors.lastname: Zhang
authors.forename: Jing-Ling
authors.initials: JL
authors.lastname: Han
authors.forename: Ji-Guang
authors.initials: JG
authors.lastname: Wang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000418:Albumins / Q000032:analysis; D000886:Anthropometry; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory; D002339:Carotid Arteries / Q000473:pathology; D003430:Cross-Sectional Studies; D004452:Echocardiography; D005260:Female; D005919:Glomerular Filtration Rate; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D006973:Hypertension / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009991:Oscillometry; D013997:Time Factors; D055815:Young Adult
chemical_list: D000418:Albumins