24 Hour Blood Pressure Measurement

24-hour blood pressure measurement (synonym: long-term blood pressure measurement) is a diagnostic method in which blood pressure is measured over a day and night at regular intervals such as 15 or 30 minutes. Blood pressure measurement can be performed on an outpatient or inpatient basis. The outpatient version is also called ambulatory blood pressure monitoring (ABDM, ABPM).

Indications (areas of application)

  • Hypertension (high blood pressure)
  • Blood pressure crises
  • Practice hypertension (white-coat hypertension)
  • Assessment of antihypertensive therapy measures
  • Allows differentiation between dipping forms:
    • “normal dipper” – normal nocturnal blood pressure drop: > 10% and < 20% of the daily mean ABMD* .
    • “non-dipper” – decreased nocturnal blood pressure drop: < 0% and < 10% of the daily mean ABMD* .
    • “extreme dipper” or “overdipper” – exaggerated nocturnal blood pressure drop: > 20% of the daily mean ABMD* .
    • “reverse dipper” (English “inverted dipper”) – inversion (reversal) of the day-night rhythm: nocturnal blood pressure drop < 0% of the daily mean, or nocturnal blood pressure rise with an inversion of the day-night rhythm.

Other indications

  • When there is a disproportion between the level of the occasional blood pressure and organ damage, for example, when an occasional blood pressure of diastolic constant ≥ 105 mmHg (moderate to severe hypertension) without high-pressure organ damage or between 90-104 mmHg (mild hypertension) with end-organ damage, respectively, is measured in practice
  • Differences of > 20 mmHg systolic and > 10 mmHg diastolic between the values measured during self-measurement of blood pressure (with correct technique) and when measured by a physician
  • Suspicion of elevated blood pressure values at night or of an abolished circadian profile, preferably in patients with secondary hypertension, for example, the particularly common renal hypertension, including diabetic nephropathy and renovascular hypertension in renal artery stenosis and in endocrine forms of hypertension (such as hyperaldosteronism, pheochromocytoma)
  • Suspected practice hypertension – regular monitoring is indicated because there is an increased risk of developing hypertension
  • Pregnancy hypertension, preeclampsia (even with only borderline elevated blood pressure).
  • Sleep apnea syndrome
  • Kidney transplantation
  • Heart transplantation
  • Hypertensive patients on rotating shift

* ABMD (= ambulatory blood pressure monitoring).

The procedure

In the 24-hour blood pressure measurement, as in the simple measurement, the blood pressure is measured on the upper arm via a cuff. This fully automatic cuff is connected to a small recorder, which registers and stores the values obtained in each case. The patient should go about his or her normal daily routine. A log kept at the same time can later show correlations between exertion and changes in blood pressure.These data are read out on the computer at the end of the examination and read out by the doctor. Definition of threshold values for hypertension in long-term blood pressure measurement:

Systolic (mmHg) Diastolic (mmHg)
Long-term blood pressure measurement (ABDM) ≥ 135 ≥ 85
Nighttime average ≥ 120 ≥ 75
24-h average ≥ 130 ≥ 80

Further notes

  • In one study, 2,600 patients with normotensive or hypertensive blood pressures were followed for approximately 6 years. Blood pressure was determined annually by 48-hour ambulatory measurement, as was the activity of the participants. This showed that nocturnal blood pressure was a strong predictor of diabetes disease risk. The lower the nighttime blood pressure, the greater the reduction in diabetes risk. In contrast, the measured blood pressure during the day had no effect on the risk.
  • A meta-analysis was able to show: Those who did not dip had a significantly higher cardiovascular risk. Those who dip only a little also had a worse cardiovascular prognosis.Depending on the defined endpoint (coronary events, apoplexes (strokes), cardiovascular mortality (death rate), and all-cause mortality), event rates were up to 89% higher; even reduced dippers still had a statistically significant increased risk of 27%.
  • In a long-term international study, nocturnal blood pressure was the most important risk factor for future cardiovascular disease or patient death, along with 24-hour mean blood pressure: Each 20-mmHg increase in systolic blood pressure increased:
    • The risk of death by 23% (HR 1.23; 95% confidence interval 1.17 to 1.28).
    • The risk of a cardiovascular event by 36% (HR 1.36; 1.30-1.43).

    The prognostic significance of nocturnal blood pressure drop (dipping) was also confirmed:

    • Extreme dipping (blood pressure falls at night by more than 20% of the daily value): over 10 years, 3.73% of patients died.
    • Normal “dipping (drop of 10 to 20%): over the course of 10 years, 4.08% died.
    • Non-dipping (drop of less than 10%): over the course of 10 years, 4.62% died
    • Reverse dipping (nighttime increase in blood pressure): over the course of 10 years, 5.76% died
  • In a cohort study, 24-hour ambulatory blood pressure measurement predicted mortality (mortality) better than individual blood pressure measurements taken by a physician:
    • Elevated systolic blood pressure in the 24-hour measurement increased mortality risk by 58% per standard deviation (hazard ratio, 1.58; 95% confidence interval, 1.56-1.60)
    • In contrast, after single measurement in the field, mortality risk increased by only 2% per standard deviation (hazard ratio, 1.02; 1.00-1.04)
  • Because nighttime elevated blood pressure is associated with a higher risk of cardiovascular events (cardiovascular-related death, myocardial infarction (heart attack), apoplexy (stroke), heart failure (heart failure)) than daytime-only hypertension, hypertensive patients with nighttime elevated blood pressure should take an antihypertensive drug primarily at bedtime.

24-hour blood pressure measurement is an important parameter in the diagnosis and treatment of hypertension and other indications.

Chronotherapy of hypertension

Therapy depending on 24-hour blood pressure measurement:

  • Take morning dose with rising

    • Antihypertensives with proven long-term efficacy in uncomplicated hypertension with a normal day-night rhythm (“normal dipper”)
  • Morning and evening dosing in cases of elevated daytime blood pressure and inadequate nighttime blood pressure reduction (“non-dipper”/”inverted dipper”).
  • Evening dose of antihypertensive combination therapy and additional calcium antagonist, alpha blocker (eg, doxazosin) or clonidine (α2-receptor agonist) in refractory nocturnal hypertension (“non-dipper”/”inverted dipper”).
  • Singular evening dose in normal daytime hypertension and nocturnal hypertension.
    • Note: No evening dosing in severe nighttime hypotension (“extreme dipper”).

Note: In case of shift work, always place the intake time at the beginning of the active phase.