Circadian systolic and diastolic differences (CSDD) and circadian modulation of 1.7-h ultradians.

In 24-h ambulatory blood pressure profiles there is overlap between the lowest systolic and the highest diastolic pressure in over 90% of the cases. An overlap is observed in about 75% of the cases when considering 90% ranges. The prominence of the 1.7-h ultradian component varies as a function of circadian stage and is found to be most prominent around mid-sleep.