At what time does supine hypertension typically begin?

Supine Hypertension Timing

Supine hypertension begins around bedtime (approximately 8:00 PM to 10:00 PM) when patients lie down for sleep. 1, 2

Pathophysiology and Timing Context

• Supine hypertension is defined as blood pressure ≥140/90 mmHg in the supine position, occurring in over 50% of patients with autonomic failure and orthostatic hypotension. 1

• The condition manifests specifically when patients assume the supine position, typically beginning in the evening hours around bedtime when transitioning from upright activities to lying flat for sleep. 3

• Nocturnal supine hypertension peaks 6-8 hours after lying down, corresponding to the middle of the night (approximately 2:00 AM to 4:00 AM if bedtime is 8:00 PM). 3

Clinical Significance of Timing

• Supine hypertension promotes nocturnal sodium excretion (pressure natriuresis), which worsens morning orthostatic hypotension by depleting intravascular volume overnight. 2, 3

• The 24-hour blood pressure pattern shows elevation during supine hours (typically 10:00 PM to 6:00 AM), with lower pressures during upright daytime hours in patients with autonomic failure. 3

• Avoiding the supine position during sleep reduces 24-hour mean blood pressure by 6.4/2.9 mmHg (systolic/diastolic), with significant reductions in both awake and sleeping blood pressure. 4

Treatment Timing Implications

• Antihypertensive medications for supine hypertension should be administered at bedtime (8:00 PM) to target the nocturnal blood pressure elevation. 3

• Clonidine 0.1 mg given at 8:00 PM produces maximal blood pressure reduction 6-8 hours later (2:00 AM to 4:00 AM), effectively targeting peak nocturnal hypertension. 3

• Head-up tilt sleeping at 10° throughout the night prevents nocturnal polyuria and maintains favorable fluid distribution in patients with orthostatic hypotension and supine hypertension. 5

Critical Clinical Pitfall

• Do not confuse supine hypertension with orthostatic hypotension—they have opposite treatment strategies. Supine hypertension improves with sitting/standing, while orthostatic hypotension worsens with sitting/standing. 5