Study shows importance of nighttime blood pressure assessment in diagnosing hypertension

About 15% of people between the ages of 40 and 75 may have an undiagnosed form of high blood pressure that only occurs at night. Because they don’t know it and therefore aren’t being treated for it, they are at higher risk of cardiovascular disease such as stroke, heart failure and even death, new research from the University suggests. from Oxford published in the British Journal of General Medicine.

When blood pressure is monitored over 24 hours, individuals can be divided into three groups based on their blood pressure pattern:

  • the “shady”, for whom the nocturnal blood pressure is lower than the daytime blood pressure (which is the case of young people in good health),
  • “non-divers”, for whom nocturnal and daytime blood pressure values ​​are not very different, and
  • the “reverse dippers”, for whom, contrary to expectations, nocturnal blood pressure is higher than daytime blood pressure, when they are upright and active.

When left undiagnosed and untreated, hypertension (also known as high blood pressure) leads to cardiovascular disease, which is a leading cause of death and disability in the UK. 1 in 8 people in England have undiagnosed high blood pressure, putting them at risk of cardiovascular disease.

24-hour blood pressure monitoring (commonly referred to as ambulatory blood pressure monitoring, ABPM) has become less common in primary care since the onset of the COVID-19 pandemic. Home blood pressure monitoring, using a monitor often purchased by individuals themselves, is the common alternative. However, home blood pressure monitors cannot be used when the person is asleep and therefore cannot measure blood pressure at night. Therefore, people whose daytime blood pressure is normal but whose nighttime blood pressure unknowingly rises at night have undiagnosed hypertension, with all the associated risks.

This new study from the University of Oxford examined 24-hour blood pressure patterns in patients admitted to hospital and found that almost half of these patients had an increase in blood pressure at night (” reverse pattern.) The study researchers then looked at the blood pressure patterns of primary care patients in the same age group (40-75 years), who had been monitored for 24 hours during their normal daily activities. using ABPM The proportion of the population in this group who were “reverse divers” was about 15% There are several possible reasons for the difference in the proportion of people with an “inverted” blood pressure pattern. reversed drop” in both patient groups. One possible reason is that the community group included a much higher proportion of people who had previously been diagnosed with hypertension, and these per sounds are more likely to be “dippers” rather than “reverse dippers”. This is because people whose blood pressure is highest during the day and drops at night are more likely to be diagnosed as having hypertension in doctors’ offices and clinics.

Main conclusions:

  • About 15% of people in the community between the ages of 40 and 75 have an increase in blood pressure at night.
  • This 24-hour pattern of blood pressure is called a “reverse drop” because the pressure increases (“reverse drop”) overnight instead of falling (“drop”), the latter being the normal pattern for healthy young people. .
  • The blood pressure of ‘reverse divers’ is lowest during the day when they have their blood pressure checked by their GP and therefore these people are at risk of not being diagnosed with hypertension.
  • Conversely, sleazy people’s blood pressure drops at night and their blood pressure is highest during the day, so they are more likely to be diagnosed with hypertension.
  • There is a body of well-established research that shows that “reverse divers” are at a higher risk of cardiovascular disease such as stroke, heart failure, and even death. The new study found that across all genders and across hospital and community patient groups, at least 1 in 3 inverted divers had at least one cardiovascular disease.

Co-author Professor Lionel Tarassenko, Professor of Electrical Engineering and Founding Director of the Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, says:
“Blood pressure follows a 24-hour cyclical pattern. Normally, it decreases (or “falls”) at night during sleep, then increases after waking up. the pattern is reversed: blood pressure rises (or “reverse dips”) at night, then falls after waking up. This means that “dipping inverters” have their lowest blood pressure during the day, and they will therefore be falsely reassured by daytime monitoring at home or in the GP’s clinic. Daytime blood pressure measurements are not enough: identifying who is a reverse diver through 24-hour ambulatory blood pressure monitoring is vital.”

Commenting on the importance of the new research findings for policy makers and clinicians, co-author Laura Armitage, PhD researcher in the Nuffield Department of Primary Care Health Sciences at the University of Oxford and practicing general practitioner , says:

“UK NICE guidelines currently recommend that GPs diagnose hypertension based on daytime blood pressure measurements alone. However, daytime blood pressure measurements are not capable of detecting high blood pressure in those high-risk patients whose blood pressure rises at night.Our research shows that measuring nighttime blood pressure could help identify 1 in 8 adults in England who have undiagnosed hypertension.Importantly, this would also lead to a reduction in cardiovascular disease and death.This underscores the need for GPs to offer blood pressure assessments of their patients.This is particularly important for people over the age of 60, as blood pressure nocturnal increases with age and office blood pressure checks and self-monitoring nce of the patient at home is not able to detect high blood pressure at night.”

The authors note several limitations to their study:

  • Choice of age group: Researchers did not find significant differences between the average systolic blood pressure of men and women during the day or night, but this may be due to the choice of age group (40-75 ). In previous work, researchers had shown that women under 60 had lower systolic blood pressure than men, but the reverse was true after age 60. age group 75 years.
  • This study used systolic blood pressure only to calculate the 24-hour blood pressure patterns of the included participants, in accordance with common practice in this field. The authors identify that future work could include an analysis to determine whether 24-hour diastolic blood pressure profiles (the force of blood against artery walls between heartbeats) provides independent information.

Failure to measure nighttime blood pressure puts all groups other than divers at risk of not identifying hypertension. We recommend that in addition to taking blood pressure measurements in the office, GPs offer home ambulatory blood pressure monitoring (ABPM) 24 hours a day to all patients aged 60 and over , when evaluating hypertension.

While we welcome the additional hypertension screening recently rolled out to pharmacies, it does not address the key issue highlighted in our article: there is a significant subset of individuals over the age of 60 who suffer from low blood pressure during the day (for example, during a pharmacy screening) but who have high blood pressure at night and therefore have a high risk of serious cardiovascular disease. These people will not be offered ABPM because of their low daytime blood pressure and will be falsely reassured. »

Laura Armitage, PhD Researcher, Nuffield Department of Primary Care Health Sciences, University of Oxford


Journal reference:

Armitage, LC, et al. (2022) Diagnosing hypertension in primary care: the importance of nighttime blood pressure assessment. British Journal of General Medicine.

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