CPAP helps lower BP in patients with sleep apnoea

Blood pressure (BP) slightly decreases in patients with obstructive sleep apnoea who undergo continuous positive airway pressure (CPAP) therapy, as seen in a study. Such effect is marginally higher in those with above-average apnea-hypopnea index (AHI).

“However, neither the severity of sleep apnoea as measured by AHI nor the extent of daytime sleepiness as measured by Epworth Sleepiness Scale (ESS) can be used to define threshold values predicting a BP decrease at least 5 mm Hg,” said lead author Maximilian Seidel, Medical Department I, University Hospital Marien Hospital Herne, Ruhr-University Bochum, Herne, Germany.

In this retrospective study, Seidel and his team explored the association of BP response to CPAP with polysomnographic readings, intensity of sleepiness, and epidemiologic parameters in 2,461 patients with obstructive sleep apnoea. BP response referred to the difference between office BP at polysomnography examinations before and after CPAP initiation.

A total of 555 patients met the eligibility criteria and were included in the analysis. Their use of CPAP had a median monthly duration of 143.7 h. BP slightly decreased at follow-up relative to baseline (128.3 vs 129.9 mm Hg; p=0.021), with a mean BP reduction of ‒1.5 mm Hg. [J Hypertens 2024;42:777-782]

This decrease in BP was more pronounced among patients with a higher than median baseline AHI (median 21) than those with a lower AHI (AHI ≥21: 128.6 vs 130.5 mm Hg; p=0.06; AHI <21: 127.9 vs 129.5; p=0.18).

In addition, CPAP therapy helped lessen sleepiness among patients (8.3 vs 6.6; p<0.0001). However, those with higher-than-median sleepiness score (ESS ≥8) showed no significant difference in BP response relative to patients with a lower sleepiness score.

In receiver-operating characteristic (ROC) curve analyses examining the accuracy of AHI and ESS to predict a BP decrease of at least 5 mm Hg, the AUC was 0.51 with AHI and 0.52 with ESS.

“Neither daytime sleepiness as measured by ESS nor the severity of sleep apnoea as measured by AHI can be used to predict a strong BP reduction at least 5 mm Hg,” Seidel said.

“The decision to initiate or not to initiate CPAP therapy in patients with sleep apnoea has, therefore, still to be based on the intention to reduce sleepiness and not to reduce BP,” he added.

BP decrease

The 2-mm Hg reduction in BP among patients who underwent CPAP therapy is consistent with meta-analysis data (2.6 mm Hg systolic and 2.0 mm Hg diastolic), in which most trials had a follow-up period of 2‒3 months. The present study, however, have a much longer follow-up period of about 1 year. [Chest 2014;145:762-771]

“Although the study is somewhat disappointing regarding the prediction of BP reductions at least 5 mm Hg, it has to be kept in mind that the observed 2-mm Hg decrease of BP is still of clinical relevance,” Seidel said. “[Based on] data from randomized controlled trials, a systolic decrease of 2 mm Hg corresponds to a 4-percent reduction of major cardiovascular events.” [Lancet 2016;387:957-967]