Clinical Significance of the Blood Pressure Changes from Day to Night

Blood pressure (BP) decreases by 10% to 20% from day to night. However, in 25% to 35% of hypertensive subjects there is some reduction in the day-night BP decline. In 3% to 5% of uncomplicated hypertensive subjects there is actually an increase, not a decrease, in BP from day to night. Many studies from independent centers showed that not only left ventricular hypertrophy, but also ventricular arrhythmias, silent cerebrovascular disease, microalbuminuria and progression of renal damage are more advanced in subjects with blunted or abolished fall in BP from day to night than in those with normal day-night BP difference. There is also evidence from longitudinal studies that a blunted, abolished or even reversed BP drop from day to night is associated with an increase in the risk of serious cardiovascular complications. However, if the quantity or quality of sleep is poor during overnight BP monitoring, night-time BP rises and its prognostic significance is no longer reliable. Studies which compared the prognostic value of daytime BP with that of night-time BP inevitably found the superiority of the latter for predicting prognosis. The exciting potential therapeutic implication that the control of night-time BP could be more rewarding, in terms of prevention of cardiovascular disease, than that of daytime BP has yet to be addressed in appropriately designed intervention trials. Of note, 24-hour ABP monitoring is the only practical way to assess the day-night rhythm of BP.