Patients who awoke at night during blood pressure monitoring were ten times less as likely to have the normal nighttime 'dip.' "Nighttime blood pressure is lower not because of the time of the day, but because people are asleep," said Agarwal. "The ambulatory monitoring technique can disturb sleep, and therefore raise the nighttime blood pressure as an artifact.

"Thus sleep quality should be taken into account when interpreting blood pressure during sleep," Agarwal added. He noted that the wristwatch actigraph provides a simple and useful way of measuring activity during 24-hour blood pressure monitoring.

This Veterans Administration study was limited to older veterans with kidney disease. "Whether similar results will be obtained in younger people remains to be seen," said Agarwal.

Source: American Society of Nephrology