What happens to your blood pressure at night?
Likely you haven’t given it that much thought. But not only is high blood pressure at night (nocturnal hypertension) a genuine phenomenon, it can also be a greater indicator of health risks than your blood pressure readings during the daytime.
Why is night-time blood pressure important?
Numerous studies have demonstrated that night-time blood pressure readings are a more accurate measurement of a person’s circulatory health: notably, the 2000 Ohasama study, 2005 Dublin outcome study, and 2010 Sleep and Hypertension study.
More recently, in 2020, the JAMP (Japan Ambulatory Blood Pressure Monitoring Prospective) study showed that people whose blood pressure rises while they’re sleeping are more likely to experience heart failure and other forms of cardiovascular disease. It also found that nocturnal hypertension can occur even among people whose daytime blood pressure is normal, making it extremely difficult to detect.
For the study, researchers studied 6,359 people. All had at least one cardiovascular risk factor and many were on medication to control their blood pressure, but none had symptomatic cardiovascular disease when the study started. Researchers used wearable monitors to measure both daytime and nighttime blood pressure.
Following up on the participants two and seven years later, researchers said that those whose nighttime systolic blood pressure reading was 20mmHg higher their daytime reading were significantly more likely to experience cardiovascular disease and heart failure. Study participants experienced a total of 306 cardiovascular events, including 119 strokes, 99 diagnoses of coronary artery disease, and 88 diagnoses of heart failure.
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Dr Kazuomi Kario, the lead author of the study and professor of cardiovascular medicine at Jichi Medical University in Tochigi, Japan, said: ‘The study highlights the importance of including nighttime blood pressure monitoring in patient-management strategies.’
Talking to Healthline, Dr Raymond Townsend, a medical expert with the American Heart Association and director of the Hypertension Program at University of Pennsylvania, said 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. It’s a window into how that person’s system is working.’
Why does my blood pressure go up at night?
A few different factors can contribute to an elevated blood pressure at night, including:
- Poor sleep quality
- Sleep apnoea
- Excess salt in the diet
- Autonomic nervous dysfunction (a condition in which the autonomic nervous system doesn’t work correctly)
- Diabetes
- Thyroid conditions
- Kidney problems
If poor sleep is to blame, there’s plenty you can do to improve the quality of your sleep and help you body get the rest it needs. Poor sleeping habits include:
- Drinking caffeine or alcohol later in the day
- Napping during the day
- Not having a consistent bedtime
- Exercising too late in the evening
- Using blue light-emitting digital devices before bed
Stressful situations, confrontations and anxiety can also impact your sleep and dreams (find out about ways to reduce stress).
What about low blood pressure at night?
It’s typical for your blood pressure to be lower at night than when you’re awake. The drop in both systolic and diastolic blood pressure (the top and bottom numbers) can be up to 20% lower than your reading in the daytime.
Low blood pressure isn’t usually seen as problematic unless it’s accompanied by other symptoms, such as dizziness or fainting. If you often feel lightheaded when getting up after sitting still or lying down for a long period, take care to sit up and get out of bed slowly in the morning. The NHS website advises that you could also try raising the head of your bed by about 15cm (6 inches) with bricks or heavy books.
Understanding your blood pressure at night
We’re very proud to have developed the only solution on the market that can easily measure blood pressure while you’re sleeping. Aktiia’s home blood pressure monitor takes readings continuously and automatically, every 90 minutes during the day and throughout the night. You won’t be aware it’s happening, so there’s no risk of anxiety about your blood pressure contributing to elevated readings.
Understanding your blood pressure and monitoring changes 24/7 is an important step towards taking control of your health. You might want to take a look at our guide on how to use a blood pressure monitor and our Blood Pressure Monitor Buying Guide.
Disclaimer: The information provided in this article is for general information purposes only and is not intended to be a substitute for professional medical advice. Always consult your physician or qualified healthcare provider for any questions related to a medical condition. The author and publisher are not liable for any harm or damage resulting from the use or misuse of the information in this article.
Sources:
Nighttime Blood Pressure Phenotype and Cardiovascular Prognosis, November 2, 2020 – https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.120.049730
Prediction of stroke by ambulatory blood pressure monitoring, July 18, 2000 – https://pubmed.ncbi.nlm.nih.gov/10930181
Superiority of ambulatory over clinic blood pressure measurement in predicting mortality, June 6, 2005 – https://pubmed.ncbi.nlm.nih.gov/15939805
Sleep and Hypertension, August, 2010 – https://journal.chestnet.org/article/S0012-3692
Nighttime Blood Pressure Phenotype, November 2, 2020 – https://www.ahajournals.org/doi/10.1161
Kazuomi Kario, Nighttime blood pressure monitoring in patient-management strategies, October, 2020 – https://www.researchgate.net/profile/Kazuomi-Kario
Raymond R. Townsend, MD, Professor CE of Medicine, January 4, 2017 – https://www.med.upenn.edu/apps/faculty/index.php/g275/p18676
How Nighttime Blood Pressure May Be More Important Than Daytime Readings, November 1, 2020 – https://www.healthline.com/how-nighttime-blood-pressure-may-be-more-important-than-daytime-readings
Trouble sleeping?, 2010 – https://www.nhs.uk/mental-health-issues/sleep/
10 stress busters, September 9, 2022 – https://www.nhs.uk/tips-to-reduce-stress
Does your blood pressure change while you sleep?, October, 2020 – https://www.bloodpressureuk.org/sleep-and-your-blood-pressure/
Low blood pressure (hypotension), November 1, 2020 – https://www.nhs.uk/conditions/low-blood-pressure-hypotension/
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