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Reliability of nocturnal blood pressure dipping
J E Dimsdale1, R von Känel, J Profant
1Department of Psychiatry, University of California, San Diego, USA. jdimsdale@ucsd.edu
Insights
Nocturnal blood pressure dipping is a reliable indicator of cardiovascular risk. This study found that measures of dipping, particularly those adjusted for individual bedtime, showed good reliability across multiple recordings.
Area of Science:
- Cardiology
- Sleep Medicine
- Hypertension Research
Background:
- Limited nocturnal blood pressure dipping is linked to increased cardiovascular disease risk.
- Understanding the reliability of measuring blood pressure dipping is crucial for clinical assessment.
Purpose of the Study:
- To evaluate the reliability of different methods for measuring nocturnal blood pressure dipping.
- To determine the most consistent approach for assessing blood pressure changes during sleep.
Main Methods:
- Ambulatory blood pressure monitoring was conducted on 17 individuals over three 24-hour periods.
- Nocturnal blood pressure dipping was assessed using three criteria: clock time, individual bedtime, and sleep time verified by polysomnography.
Main Results:
- All three methods for measuring blood pressure dipping demonstrated adequate reliability.
- Correlation coefficients between testing occasions ranged from 0.5 to 0.8, indicating consistent results.
- Reliability varied slightly depending on the dipping criterion and blood pressure measurement (systolic, diastolic, or mean arterial).
Conclusions:
- Blood pressure dipping is a reliable physiological construct.
- While all measures showed reliability, adjusting the definition of 'night' to individual bedtime is recommended.
- Systolic blood pressure dipping showed slightly lower reliability compared to diastolic or mean arterial pressure dipping.
Background:
Increasing evidence documents the fact that individuals whose blood pressure drops or 'dips' relatively little at night have a higher risk of numerous cardiovascular illnesses.
Objective:
To examine the reliability of various measures of nocturnal blood pressure dipping.
Methods:
This study examined 17 individuals with ambulatory blood pressure monitoring on three 24 h recordings while they pursued a schedule similar to that of in-patients on a clinical research unit. Nocturnal dipping of blood pressure was scored three ways: as the drop in blood pressure between 10 p.m. and 6 a.m. ('clocktime'), as the drop in blood pressure tailored to each individual's reported bedtime ('bedtime'), and as the drop in blood pressure accompanying polysomnographically verified sleep ('sleeptime').
Results:
Adequate reliability was obtained for all three measures of dipping. There was, in general, a significant correlation across testing occasions (P<0.05). The correlation coefficient ranged from 0.5 to 0.8, depending on which criterion of dipping was selected and whether the endpoint was systolic blood pressure, diastolic blood pressure, or mean arterial blood pressure.
Conclusions:
The reliability of systolic blood pressure dipping was somewhat lower than that of diastolic or mean arterial blood pressure dipping. Dipping appears to be a reliable construct. While no one definition of dipping was demonstrably better than another, the most sensible definition of dipping would allow some adjustment for defining 'night' on the basis of each individual's idiosyncratic bed time.