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Who are the non-dippers? A better definition via the blood pressure circadian rhythm
1Institute of II Medical Clinic, University of Rome La Sapienza, Italy. cugini@axrma.uniromal.it
Insights
Non-dipping phenomenon (NDP) in blood pressure (BP) is better understood through circadian rhythm (CR) analysis. Rhythmometric analysis is crucial for identifying abnormal BP time structures in non-dippers.
Area of Science:
- Cardiovascular Physiology
- Chronobiology
- Hypertension Research
Background:
- The non-dipping phenomenon (NDP) represents a significant deviation in blood pressure (BP) circadian rhythm (CR).
- Understanding NDP requires considering the inherent within-day variability of BP as a manifestation of CR.
Purpose of the Study:
- To investigate the non-dipping phenomenon (NDP) in relation to blood pressure (BP) circadian rhythm (CR).
- To analyze ambulatory BP monitoring data from hypertensive and normotensive subjects to characterize NDP within the context of BP CR.
Main Methods:
- Ambulatory BP monitoring data from 298 essential hypertensive patients (EHP), 84 secondary hypertensive patients (SHP), and 93 normotensive subjects (NS) were analyzed.
- Subjects were classified as 'rhythmic' (R) or 'non-rhythmic' (NR) based on rhythmometric validation of their BP CR.
Main Results:
- Non-dippers (ND) were identified in EHP (14%), SHP (27%), and NS (16%).
- Rhythmic non-dippers (R ND) showed nocturnal phase-shifts, amplitude increases, or mesor increases in BP CR.
- Non-rhythmic non-dippers (NR ND) exhibited negligible amplitude and increased mesor, particularly in hypertensive groups.
Conclusions:
- The identification criteria for NDP may not be sufficient for inferring BP CR in hypertensive or normotensive individuals.
- Rhythmic characteristics of ND highlight the fundamental importance of rhythmometric analysis for detecting abnormal BP time structures.
Objective:
The non-dipping phenomenon (NDP) can be better interpreted when considering that blood pressure (BP) shows a within-day variability which is the expression of a circadian rhythm (CR).
Patients And Methods:
The NDP was investigated at the light of the BP CR by analysing the ambulatory BP monitoring of 298 essential hypertensive patients (EHP), 84 secondary hypertensive patients (SHP), as well as 93 normotensive subjects (NS). According to the rhythmometric validation, the investigated subjects were defined "rhythmic" (R) or "non-rhythmic" (NR).
Results:
The non-dippers (ND) were found among not only the EHP (14%) and SHP (27%) but also the NS (16%). The percentages of R ND were 9%, 4% and 20%, respectively in EHP, SHP and NS. The R ND were characterized by a nocturnal phase-shift (100% in NS), associated with an amplitude increase (50% in EHP) or a mesor increase (50% in EHP; 100% in SHP) in BP CR. The NR ND were characterized by an amplitude almost negligible (100% in NS) associated with a mesor increase (100% in EHP; 100% in SHP).
Conclusions:
The detection of a NDP associated with a rhythmicity suggests that the criterion with which the ND are identified cannot be used for making inferences on the BP CR in HP or NS. The rhythmic characteristics in ND suggest that the rhythmometric analysis is fundamental for identifying the abnormal time structure of BP 24-h values in the presence of the NDP.