[Nocturnal fall in arterial blood pressure in normotensive subjects: individual characteristic or the effect of daily activity?].
BACKGROUND
The interpretation of the absence of a nocturnal fall in blood pressure (BP) (non-dipper condition) and its possible prognostic value are not clear. One possible hypothesis to be analyzed is whether the condition of non-dipper is due or not to the daily activity.


METHODS
Ninety-five doctors, 47 of whom were females, whose age ranged between 24 and 46 years participated in the study. Ambulatory monitoring BP were programmed to be randomly carried out on-call and on a day-off with measurements intervals of 15 min. Mean systolic BP (SBP), diastolic BP (DBP) and heart rate (HR) were considered as measurement parameters for every period: 24 h, awake and sleep. Sleep period was considered as one of no less than 2 hours, nocturnal BP fall was defined as the difference between awake and sleep means, and dipper condition as a systolic decrease greater than 10 mmHg and diastolic decrease greater than 5 mmHg.


RESULTS
The mean nocturnal BP fall on the day-off was of 15% and 13% (SBP and DBP) and while on-call it was 18% and 15% respectively (p < 0.001). In absolute values the SBP decreased 21 +/- 10 mmHg and 18 +/- 10 mmHg and the DBP 11 +/- 6 mmHg and 10 +/- 5 mmHg, on-call and day off respectively (p < 0.001). The percentage of subjects with decrease lower than 10/5 mmHg was different in each of the two days (8% and 12%), however only one individual maintained the non-dipper condition in both period, although he reported many interruptions in the sleep. No association was established between the nocturnal BP fall and other variables (age, sex or family history of hypertension).


CONCLUSIONS
The non-dipper condition is changeable and is related to the activity carried out by the subject while awake, as well as the quality of sleep. It does not seem to be associated with inherent variables of the individual such as family history of hypertension, age or sex.
del Arco-Galán
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Servicio de Medicina Interna, Hospital de la Princesa, Universidad Autónoma, Madrid.
Suárez Fernández
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D000203:Activities of Daily Living; D000328:Adult; D001794:Blood Pressure; D015924:Blood Pressure Monitors; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012890:Sleep; D014851:Wakefulness
Caída nocturna de la presión arterial en normotensos: rasgo individual o efecto de la actividad diurna?