The diastolic blood pressure J-curve revisited: An update.

Hypertension remains a leading cause of morbidity and mortality. Recent treatment guidelines stress more strict systolic blood pressure (SBP) targets without regard for abnormally low achieved diastolic blood pressures (DBP). However, as DBP falls below a critical level, adverse events increase, the so-called J-shaped curve. Proponents argue that the low DBP is causative due to reduced coronary perfusion during diastole with obstructive coronary artery disease (CAD), whereas others postulate the J-curve represents reverse causality from underlying comorbidity. Most data are observational, derived from population-based cohorts or post-hoc analyses of randomized controlled trials (RCT) conducted for other reasons. The purpose of this review is to analyze the observational studies performed over the last decade addressing the J-curve, with consideration of earlier data. Overall, a J-curve exists, but it remains uncertain whether low DBP is causative or instead reflects reverse causation from either diseased vasculature (widened pulse pressure) or severe underlying comorbidity. The most convincing data for causation come from studies restricted to patients with documented CAD, with evidence suggesting revascularization may mitigate risk. RCTs are needed to determine if a low DBP should preclude intensification of therapy, especially with documented CAD. Firm recommendations cannot be made with contemporary data.