Blood pressure monitoring and sleep

Which one would it be – blood pressure problems or a good night’s sleep?

The so-called ambulatory blood pressure (BP) monitoring technique measures BP 24 hours a day. It assesses the variations in BP during daytime and at night. Sleeping BP, i.e. BP measured during sleep is a good indicator of risk for heart attack and stroke. Normally, BP is lower at night compared to that measured at daytime. When sleeping BP doesn’t “take a dip”, then the risk for cardiovascular problems is much greater. To continuously measure BP, patients are equipped with adevice called actiwatch or a wristwatch actigraph, which is the size of a wristwatch and is worn like one.

However, how do this widely used test and the device affect the sleep of the patients? A recent study reveals that the BP monitoring device can actually disturb the patients’ nighttime rest, thus questioning the validity of the measurements.

According to Dr. Rajiv Agarwal of the Indiana University and Veterans Affairs Medical Center in Indianapolis

“Blood pressure (BP), measured during sleep correlates better with heart attacks and strokes compared to blood pressure measured in the doctor’s office. However, if blood pressure measurement disturbs sleep, then it may weaken the relationship between ‘sleeping BP’ and these cardiovascular events.”

The study followed up 103 elderly patients with kidney disease equipped with actiwatches. The results revealed that

• the BP monitoring device disturbed most of the patients
• the participants spent, on average, 90 minutes less time in bed
• the participants spent less time sleeping and slept less efficiently
• some participants awoke at night

According to the researchers, the dip in night time BP measurements is due to sleep. However, if a patient cannot sleep due to whatever disturbance, then night time BP may be abnormally high.

The researchers are therefore warning about jumping into conclusions about interpreting the results of ambulatory BP monitoring.

Dr. Agarwal continues

“Thus sleep quality should be taken into account when interpreting blood pressure during sleep… Whether similar results will be obtained in younger people remains to be seen.”

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