BLOOD-PRESSURE DURING SIESTA - EFFECT ON 24-H AMBULATORY BLOOD-PRESSURE PROFILES ANALYSIS

Blood pressure (BP) during siesta declines to levels similar to those of night time sleep. The objective of the study was to assess the effe ct of siesta on 24-h ambulatory BP (ABP) data. Two different approache s were employed for the definition of day and night periods: (1) actua l patient reported day and night intervals (ACT) with siesta period an alysed as a third time period; and (2) arbitrary day and night time in tervals (ARE) with the presence of siesta being ignored. A total of 20 3 24-h ABP recordings were analysed, with a siesta during ABP monitori ng reported in 154 of them. Mean siesta BP was very close to ACT night time BP. Among recordings with a siesta, ACT daytime BP was higher an d night time BP lower than the corresponding ARE BPs (P < 0.001). The magnitude of night time BP drop was greater with ACT intervals, result ing in a lower percentage of non-dippers (P < 0.001). Among 49 recordi ngs without a siesta, differences between ACT and ARE BPs were less pr onounced for daytime but not for night time. Differences in the magnit ude of nocturnal BP drop between ACT and ARE periods, although statist ically significant, did not affect the prevalence of non-dippers. In c onclusion, analysis of 24-h BP profiles by using ARE instead of ACT da y and night intervals results in underestimation of the nocturnal BP d rop and overestimation of the proportion of non-dippers. This bias is more pronounced in patients who take a siesta during ABP monitoring.