Response to Why Is Nondipping in Ambulatory Blood Pressure Monitoring Not Prognostic in Poor Sleepers?
In their elegant study carried out in a sleep laboratory, these authors found that systolic and diastolic blood pressure (BP) values were 5 mm Hg lower during uninterrupted sleep than during brief awakenings induced by cuff inflations. In our study, nighttime systolic BP was 5 mm Hg higher and diastolic BP 4 mm Hg higher in the subjects who perceived a sleep deprivation >4 hours as compared with subjects who did not complain of sleep disturbances.
Other studies carried out in sleep laboratories provided consistent results. For example, Pedullà et al4 found an association between number of microarousals and a blunted day-night BP rhythm. Portaluppi et al5 found a higher number of episodes of sleep apnea and snoring in nondippers than in dippers.
Nighttime BP could no longer be predictive of cardiovascular events in poor sleepers, because it was reset to randomly higher levels in these subjects, possibly as a result of compressive, tactile, and sonorous stimuli produced by cuff inflations. The true differences in nighttime BP between dippers and nondippers might turn into random differences during overnight BP monitoring in poor sleepers.
However, contrary to interpretation by Martinez and Fuchs, we would be more cautious in extrapolating implications from the study by Kripke et al6 on the relation between sleep duration and mortality. In that study, a J-shaped relation was observed between duration of sleep and risk of mortality, with the highest risk of death in people who slept >8 hours or <6 hours per night, and the best survival among those sleeping ≈7 hours per night.6 The relevance of these data to episodic sleep alterations induced by overnight BP monitoring in one or a few more occasions during life looks virtually absent.
Overall, these studies suggest that nighttime BP recorded by noninvasive monitoring is ≈5 mm Hg higher during awakenings than during uninterrupted sleep. In the general practice and out of sleep laboratories, caution is needed in interpreting nighttime BP levels in poor sleepers (ie, subjects who perceive a sleep deprivation >4 hours) during overnight BP monitoring.
Martinez D, Fuchs F. Why is nondipping in ambulatory blood pressure monitoring not prognostic in poor sleepers? Hypertension. 2007; 50: e20.
Verdecchia P, Angeli F, Borgioni C, Gattobigio R, Reboldi G. Ambulatory blood pressure and cardiovascular outcome in relation to perceived sleep deprivation. Hypertension. 2007; 49: 777–783.