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Experts say having higher blood pressure readings while you sleep could be an indication of a higher risk of heart disease. Maskot/Getty Images
  • Researchers reported that people whose blood pressure rises while they’re sleeping have a higher risk for cardiovascular disease.
  • Experts say nighttime blood pressure readings are a more accurate measurement of a person’s circulatory health.
  • They urge medical professionals to have people’s blood pressure monitored during sleep periods.
  • They said regular sleeping patterns as well as lower salt intake can help lower nighttime blood pressure readings.

You might think that your body is most at ease while you’re asleep.

But some people can have spikes in blood pressure while they slumber that can have potentially deadly consequences.

People who experience high blood pressure while sleeping, a condition called nocturnal hypertension, are more likely to experience heart failure and other forms of cardiovascular disease, according to a new study published today in the journal Circulation.

Nocturnal hypertension can occur even among people whose daytime blood pressure is normal.

This dangerous condition is difficult to catch, as routine blood pressure checks are almost always done during daytime hours.

“Results indicate that nighttime systolic blood pressure was a significant, independent risk factor for cardiovascular events,” said Dr. Kazuomi Kario, the lead author of the study and a professor of cardiovascular medicine at Jichi Medical University in Tochigi, Japan.

“The study highlights the importance of including nighttime blood pressure monitoring in patient-management strategies and will hopefully encourage physicians to ensure that antihypertensive therapy is effectively lowering blood pressure throughout the 24-hour dosing period.”

For the study, Japanese researchers studied 6,359 people, using wearable monitors to measure both daytime and nighttime blood pressure.

The participants all had at least one cardiovascular risk factor, and most were taking medication to control their blood pressure. However, none had symptomatic cardiovascular disease when the study started.

During 2-year to 7-year follow-ups of the participants, researchers said they found those who had nighttime systolic blood pressure that was 20 millimeters of mercury (mm Hg) above their daytime systolic reading were significantly more likely to experience atherosclerotic cardiovascular disease and heart failure.

Overall, study participants experienced a total of 306 cardiovascular events, including 119 strokes, 99 diagnoses of coronary artery disease, and 88 diagnoses of heart failure.

Conversely, participants whose blood pressure was controlled with medication had an increased risk of stroke if their blood pressure dipped too low at night, the study found.

A previous study by Kario and colleagues also showed that low blood pressure while sleeping increased stroke risk.

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.

Dr. Victoria Shin, a cardiologist at Torrance Memorial Medical Center in California, told Healthline that this and other research has led more physicians to direct patients to take their blood pressure medication at night.

“Taking blood pressure medication in the evening improves blood pressure throughout [the night and day] and reduces mortality overall,” she said.

Kario said that sympathetic nervous activation, autonomic nervous dysfunction, sleep apnea, and poor sleep quality may also contribute to increase nocturnal blood pressure.

“Poor sleeping habits include drinking caffeine or alcohol later in the day, napping during the day, non-consistent bedtime, poorly controlled sugar, prostate hypertrophy, exercising too late in the evening, blue light from your digital device, dreams, or emotional confrontations (like an argument with your partner or spouse or any other anxiety-producing situation),” said Dr. Leonard Pianko, a cardiologist in Miami, Florida.

Medical conditions that can trigger a spike in your nocturnal blood pressure include diabetes, thyroid, and kidney problems, Pianko added.

Kario recommends reducing salt intake, administrating diuretics, and taking mineral corticoid receptor blockers to help reduce risk of nocturnal hypertension.

He added that follow-up studies are needed on interventions to maintain normal nocturnal blood pressure levels.

“The most important way to lower your risk of an acute nocturnal spike in your blood pressure is to maintain a consistent sleeping pattern,” added Pianko.

“Try to go to sleep and get up at the same time each day. Avoid alcohol and caffeine before bed. Exercise earlier in the day. Avoid the blue light of digital devices before bedtime. Seek help for anxiety and consider meditation or similar activities to control stressful situations.”