Overnight Reduction or Surge in Blood Pressure
Optimal blood pressure fluctuates over a 24-hour sleep-wake cycle, with values rising in the daytime and falling after midnight. The reduction in early morning blood pressure compared with average daytime pressure is referred to as the night-time dip. Ambulatory blood pressure monitoring may reveal a blunted or abolished overnight dip in blood pressure. This is clinically useful information because non-dipping blood pressure is associated with a higher risk of left ventricle hypertrophy and cardiovascular mortality. By comparing the early morning pressures with average daytime pressures, a ratio can be calculated which is of value in assessing relative risk. Dipping patterns are classified by the percent of drop in pressure, and based on the resulting ratios a person may be clinically classified for treatment as a "non-dipper" (with a blood pressure drop of less than 10%), a "dipper," an "extreme dipper," or a "reverse dipper," as detailed in the chart below. Additionally, ambulatory monitoring may reveal an excessive morning blood pressure surge; which is associated with increased risk of stroke in elderly people with high blood pressure.
Classification of dipping in blood pressure is based on the American Heart Association's calculation, using systolic blood pressure (SBP) as follows:
| Range | Class |
|---|---|
| <0% | Reverse Dipper |
| 0% - 10% | Non-Dipper |
| 10% - 20% | Dipper |
| >20% | Extreme Dipper |
Read more about this topic: Ambulatory Blood Pressure
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