Night-time blood pressure assessment should be carried out among people with suspected hypertension because of the prevalence of “reverse dipping”, a new study has shown.
Research by the University of Oxford says ambulatory blood pressure monitoring (ABPM) – rather than at-home monitoring systems – should be used to enable 24-hour monitoring because home systems cannot be used when asleep.
The researchers, writing in the British Journal of General Practice, say when they looked at 24-hour blood pressure patterns in patients aged 40-75 admitted to hospital, they found almost half had a blood pressure rise at night, the reverse dipper pattern.
When they examined blood pressure patterns from patients in primary care from the same age group, who had been monitored for 24 hours during their normal daily activities using ABPM, the proportion of reverse dippers was 15%.
The team hypothesises several possible reasons for the difference in the proportion of people found to have a reverse dipping blood pressure pattern in the two patient groups, including that the community group included a higher proportion of people who had already been diagnosed with hypertension. These individuals are more likely to be dippers rather than reverse dippers.
They warn because blood pressure for reverse dippers is lowest during daytime, when they would have their blood pressure checked by their GP, they are at risk of having a missed diagnosis of hypertension, while dippers, whose blood pressure decreases during the night, are more likely to be diagnosed with hypertension.
Co-author Professor Lionel Tarassenko, professor of electrical engineering and founder director of the Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, says: “Day-time blood pressure measurements are not enough: it is vitally important to identify who is a reverse dipper through 24-hour ambulatory blood pressure monitoring.”
Dr Laura Armitage, co-author, doctoral research fellow of the University of Oxford’s Nuffield Department of Primary Care Health Sciences and a practising GP, says: “The UK NICE Guidelines presently recommend GPs diagnose hypertension based on day-time blood pressure measurements only.
“However, day-time blood pressure measurements are not capable of detecting high blood pressure in these highest-risk patients whose blood pressure rises at night.
“Our research shows that measuring night-time blood pressure could help identify the one in eight adults in England who have undiagnosed hypertension. Importantly, this would also lead to a reduction in cardiovascular disease and death.
“This highlights the need for GPs to offer 24-hour blood-pressure assessment to their patients. This is particularly important for those above the age of 60, as the higher night-time blood pressure increases with age and blood pressure checks in the surgery and patient-self monitoring at home is not capable of picking up high night-time blood pressure.”
The researchers recommend that in addition to taking blood pressure measurements in the surgery, GPs should offer 24-hour, at-home ABPM to all patients aged 60 and over as a minimum, when assessing for hypertension.
“Whilst we welcome the additional screening for hypertension recently deployed in pharmacies, it does not address the key issue highlighted in our paper: there is a substantial sub-set of individuals above the age of 60 who have low blood pressure during the day (for example, when screened in the pharmacy) but who have an elevated night-time blood pressure and hence a high risk of serious cardiovascular disease. Those individuals will not be offered ABPM because of their low day-time blood pressure and will be falsely reassured,” added Dr Armitage.
Armitage LC, Davidson S, Mahdi A et al. Diagnosing hypertension in primary care: the importance of night-time blood pressure assessment. British Journal of General Practice 21 September 2022
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