Blood pressure variability in OSA – data from four randomised-controlled CPAP-withdrawal trials

Background Increased daytime blood pressure variability (BPV) is associated with cardiovascular risk. Preliminary data suggests that obstructive sleep apnoea (OSA) might contribute to increased daytime BPV. Objective The aim of this study was to evaluate the effect of continuous positive airway pressure (CPAP) therapy withdrawal on daytime BPV. Methods 183 patients previously diagnosed with OSA and treated with CPAP were randomised to either continue or withdraw CPAP within four trials. Office morning BP was measured in triplicate at baseline and follow-up (day 14). In addition, participants performed BP measurements at home on a daily basis (days 1-13). The main outcome of interest was the treatment effect on within-visit-BPV expressed as standard deviation (SD) of triplicate measurements. Additional outcomes included morning home BPV and day-to-day home BPV. Results Within-visit variability of systolic BP significantly increased in response to recurrence of OSA in the CPAP-withdrawal group (difference between groups in SD of systolic BPV +1.14 mmHg, 95%CI +0.20/+2.09, p=0.02). There was no statistically significant effect on within-visit variability of diastolic BP (p=0.38) or heart rate (p=0.07). Neither morning home BP variability (systolic BPV, p=0.81; diastolic BPV, p=0.46) nor day-to-day variability of home BP measurements (systolic BPV, p=0.61; diastolic BPV, p=0.58) differed significantly between groups. Conclusion CPAP withdrawal results in a minor increase of within-visit variability of office systolic BP but has no effect on home BPV or day-to-day BPV. Although the treatment effect may be blunted by antihypertensives, it is unlikely that OSA contributes to cardiovascular risk via elevated daytime BPV.