Kario told Healthline that blood pressure rises naturally to excrete excess sodium from the kidneys, particularly among people with high sensitivity to salt intake.
“Usually, high daytime blood pressure is enough to excrete the sodium,” he said. “However, in the subjects with increased circulating blood volume (due to increased salt intake and salt sensitivity), blood pressure needs to increase not only during daytime but also nighttime to excrete the sodium from the body. This is the compensated mechanism, but it’s harmful to the heart.”
Dr. Raymond Townsend, a medical expert with the American Heart Association and director of the Hypertension Program at University of Pennsylvania, told Healthline that ideally all blood pressure measurements would be taken at night, not during the day.
“When you’re asleep at night, it’s the purest time for blood pressure,” he said. “It’s a window into how that person’s system is working.”
Townsend, who has administered thousands of nighttime blood pressure tests, said there’s potential for using consumer devices for at-home blood pressure monitoring.
A device called the WatchBP Home from Microlife, for example, can provide up to three nocturnal blood pressure results per night.