Obstructive sleep apnoea during REM sleep and incident non-dipping of nocturnal blood pressure: a longitudinal analysis of the Wisconsin Sleep Cohort

Abstract

Background: Non-dipping of nocturnal blood pressure (BP) is associated with target organ damage and cardiovascular disease. Obstructive sleep apnoea (OSA) is associated with incident non-dipping. However, the relationship between disordered breathing during rapid eye movement (REM) sleep and the risk of developing non-dipping has not been examined. This study investigates whether OSA during REM sleep is associated with incident non-dipping.

Methods: Our sample included 269 adults enrolled in the Wisconsin Sleep Cohort Study who completed two or more 24 h ambulatory BP studies over an average of 6.6 years of follow-up. After excluding participants with prevalent non-dipping BP or antihypertensive use at baseline, there were 199 and 215 participants available for longitudinal analysis of systolic and diastolic non-dipping, respectively. OSA in REM and non-REM sleep were defined by apnoea hypopnoea index (AHI) from baseline in-laboratory polysomnograms. Systolic and diastolic non-dipping were defined by systolic and diastolic sleep/wake BP ratios >0.9. Modified Poisson regression models estimated the relative risks for the relationship between REM AHI and incident non-dipping, adjusting for non-REM AHI and other covariates.

Results: There was a dose-response greater risk of developing systolic and diastolic non-dipping BP with greater severity of OSA in REM sleep (p-trend=0.021 for systolic and 0.024 for diastolic non-dipping). Relative to those with REM AHI<1 event/h, those with REM AHI≥15 had higher relative risk of incident systolic non-dipping (2.84, 95% CI 1.10 to 7.29) and incident diastolic non-dipping (4.27, 95% CI 1.20 to 15.13).

Conclusions: Our findings indicate that in a population-based sample, REM OSA is independently associated with incident non-dipping of BP.

Keywords: Sleep apnoea.

Figure 1.. Flow chart of the study

ABPM: Ambulatory blood pressure monitoring, PSG: polysomnogram, REM: rapid eye movement, AHI: apnea-hypopnea index, CPAP: continuous positive airway pressure

Figure 2.

Relative risks and 95% confidence intervals from modified Poisson regression models quantifying the independent association between REM apnea-hypopnea index (AHI) severity categories and incident systolic and diastolic nondipping (panels A and B) over an average follow-up of 6.6 years. Models are adjusted for age, sex, race, body mass index, waist-to-hip ratio, current smoking, alcohol consumption, and Log₂(NREM AHI + 1) which allows for the coefficients to be interpreted as the “effect” of a 2-fold increase in NREM AHI (1 was added to NREM AHI in the argument of the logarithm to allow for analysis of zero values). NREM AHI was not significant in these two models. Panels C and D explore the association between NREM AHI severity categories and incident nondipping adjusted for age, sex, race, body mass index, waist-to-hip ratio, current smoking, alcohol consumption, and Log₂(REM AHI + 1). NREM AHI categories were not associated with incident systolic or diastolic nondipping. In contrast, doubling of REM AHI had a relative risk of 1.37 (95% CI 1.13-1.65; p=0.0011) for incident systolic nondipping and 1.50 (95% CI 1.17-1.93; p=0.0015) for incident diastolic nondipping. Panels E and F illustrate the association between incident nondipping and total AHI categories adjusted for age, sex, race, body mass index, waist-to-hip ratio, current smoking, and alcohol consumption. Increasing total AHI categories was independently associated with incident systolic nondipping, but not diastolic.