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.
Conclusion: BP load was associated with target organ damage, but not independently of BP level.