Three to four nocturnal BP measurements match full night of ambulatory BP monitoring

Measuring blood pressure (BP) three or four times while asleep may allow for a reasonably accurate detection of nocturnal hypertension status as compared with a full night of ambulatory BP monitoring (ABPM), a recent study has found.

Researchers drew data from the Jackson Heart (n=621) and Coronary Artery Risk Development in Young Adults (n=458) studies, looking at 74 different sampling approaches to estimate BP during sleep and compared them against ABPM. The outcome of interest was the chance-corrected agreement for the detection of nocturnal hypertension, defined as mean asleep systolic BP ≥120 mm Hg or diastolic BP ≥70 mm Hg.

The majority of BP sampling techniques underestimated both nocturnal systolic and diastolic BP by 1–2 mm Hg relative to a full night of ABPM. In the combined cohort, 14 BP sampling methods achieved an estimated kappa statistic ≥0.80, suggesting high agreement with ABPM.

Kappa values showed substantial variation depending on the timing of measurement. For instance, BP sampling in the hours after falling asleep yielded estimates ranging from 0.69–0.83, while measurements following midnight had kappa values of 0.69–0.81.

Notably, BP sampling 1, 2, 4, and 5 hours after falling asleep yielded the highest kappa value of 0.84 (95 percent confidence interval [CI], 0.81–0.87). Relative to night-time ABPM, such sampling method yielded systolic and diastolic BP measurements that differed by an average of 3.11 and 2.66 mm Hg, respectively.

“Future studies may choose to measure BP three to four times during sleep instead of 16 or more times that occurs with a full night of ABPM, as this could improve study recruitment and increase the likelihood of participants agreeing to have their sleep BP assessed over multiple nights,” the researchers said.

“The results from the current study also suggest that home BPM devices programmed to measure BP at specific times during sleep or after midnight may be a reasonable substitute for a full night of ABPM,” they added.