Background: The prognostic significance of abnormal circadian blood pressure (BP) patterns is well established. Research to date has focused on both nocturnal dipping and absolute night-time BP levels; however, which of these variables should be the primary target for therapy remains unclear. The aim of this study is to determine whether dipping status or absolute night-time BP levels have a stronger association with subclinical target organ damage (TOD).
Methods: The Mitchelstown Cohort was established to examine cardiovascular health in an adult population sample recruited from primary care. Night-time BP was categorized by dipping status. Subclinical TOD was defined as Cornell Product left ventricular hypertrophy (LVH) voltage criteria on ECG and urine albumin : creatinine ratio (ACR) at least 1.1 mg/mmol. Multivariable logistic regression analysis was used to assess the association between night-time BP and TOD.
Results: Of 2047 participants, 1207 (response rate 59%), underwent 24-h ambulatory BP monitoring. We excluded 161 studies due to incomplete data. Of 1046 participants, 178 (17%) had evidence of TOD. Each 10-mmHg rise in night-time SBP increased the odds of TOD. Odds ratio (OR) ACR at least 1.1 mg/mmol 1.5 [95% confidence interval (95% CI) 1.2-1.8] and OR LVH 1.4 (95% CI 1.1-1.8).
Conclusion: Absolute BP level rather than dipping status may be a superior early marker of risk associated with night-time BP. Interventional studies are required to determine whether there is a benefit in specifically targeting absolute night-time BP levels to prevent clinically important outcomes.