During my Hypertension clinic last week, I saw a patient coming in for an assessment after completing an Ambulatory Blood Pressure Monitoring (ABPM) test. On reviewing his test results, it was evident that he met the diagnostic threshold for hypertension (daytime mean > 135/85 and/or 24-hour mean > 130/80). However, on taking a closer look at his test data, I noticed that his BP measurements did not show the typical nocturnal dip we expect to see and in fact his average night time BP was higher than his daytime average. I decided to do some additional research to determine the implications of these results.
While ABPM is recommended in all patients suspected of having hypertension, often times daytime BP measurements are used as the basis to make diagnostic/management decisions, overlooking important information from abnormal BP patterns throughout a 24 hour period. Past research has shown that nighttime BP better represents baseline BP measurement and cardiovascular risk stratification is more accurate if based on nighttime BP levels. Nocturnal patterns in BP can also have significant implications in a patient's overall health.
The concept of "dipping status" refers to the change in BP from wakefulness to sleep. In healthy physiologic conditions, we expect to see a decline in BP during this shift. However, in some patients, this nocturnal decline or dipping may be absent and the BP is not able to reach what would be considered the appropriate "basal" level during sleep; this is described as non-dipping. Past studies have shown that a decrease in nocturnal BP of <10% is associated with increased risk of cardiovascular events, both in normotensive and hypertensive patients. In other instances referred to as reverse-dipping or rising, the BP during sleeping hours can actually rise and be higher than the daytime average BP. These are the patients who are at highest risk. Each 10 mmHg increase in the mean nighttime systolic BP results in a 21% increase in mortality risk. Increase in nighttime BP can also be an indication of pathologic conditions such as obstructive sleep apnea (OSA).
With these findings that certain nocturnal BP patterns may be associated with an adverse prognosis, there is overall agreement that treating nocturnal hypertension can have significant benefits for optimal BP control as well as overall cardiovascular health.
Interestingly, the recent Hygia Chronotherapy Trial tested the hypothesis of whether taking the entire daily dose of BP-lowering medications at bedtime promotes better BP control and protects against major cardiovascular events compared to ingestion of all BP-lowering medications in the morning on awakening. Results of the study showed that the bedtime-treatment regimen resulted in a significantly greater decline in BP during sleep-time and the proportion of patients with the higher risk non-dipper BP patterns was significantly lower when compared to the upon-wakening treatment regimen (37% vs. 50%, P < 0.001). As such, bedtime hypertension treatment is a simple strategy that we can use with patients to achieve therapeutic goals of adequate sleep-time BP reduction while shifting sleep-time BP decline towards the normal physiologic dipper BP pattern.
In the case of my patient, his reverse dipping pattern is important to acknowledge in order to investigate for the possibility of pathologic conditions such as OSA as well as counsel around taking his BP medications at bedtime, a simple change that can improve his BP control and reduce risk of cardiovascular events.
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References:
O'Brien E, Kario K, Staessen JA, de la Sierra A, Ohkubo T. Patterns of ambulatory blood pressure: clinical relevance and application. The Journal of Clinical Hypertension. 2018 Jul;20(7):1112-5.
Hermida RC, Crespo JJ, Domínguez-Sardiña M, Otero A, Moyá A, Ríos MT, Sineiro E, Castiñeira MC, Callejas PA, Pousa L, Salgado JL. Bedtime hypertension treatment improves cardiovascular risk reduction: the Hygia Chronotherapy Trial. European heart journal. 2020 Dec 21;41(48):4565-76.
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