Reduced REM sleep independently predicted higher all-cause mortality (hazard ratio 2.39) in revascularized coronary artery disease patients with obstructive sleep apnea over a median 4.7-year follow-up.
Key Findings
Results
The lowest quartile of REM sleep percentage corresponded to 8.7% of total sleep time, and participants in this group had significantly higher all-cause mortality than those above this threshold.
Mortality was 12.8% in the reduced REM group (n=86) versus 4.4% in the higher REM group (n=270), p=0.006
The study included 356 revascularized CAD patients with OSA (AHI ≥15 events/h) and total sleep time ≥240 min on baseline polysomnography
Median follow-up was 4.7 years
This was a secondary analysis of the RICCADSA trial
Results
Reduced REM sleep independently predicted all-cause mortality after adjustment for age, sex, BMI, and CPAP allocation.
Hazard ratio 2.39; 95% CI 1.03–5.56; p=0.043
The association remained after further adjustment for total sleep time, slow-wave sleep, baseline AHI, coronary bypass surgery, atrial fibrillation, and REM-AHI interaction
Cox proportional hazards models were used to assess the association
The independent prediction was maintained across multiple model specifications
Results
Participants with reduced REM sleep differed significantly from those with higher REM sleep on multiple demographic and polysomnographic characteristics.
Reduced REM group was older (66.0 ± 8.1 vs. 63.0 ± 8.0 years; p=0.035) and had higher BMI (29.8 ± 4.6 vs. 28.7 ± 3.8 kg/m²; p=0.010)
Reduced REM group had shorter total sleep time (369 ± 77 vs. 497 ± 69 min; p<0.001)
Reduced REM group had less slow-wave sleep (5.2 ± 7.0% vs. 8.1 ± 10.0%; p=0.007)
Reduced REM group had higher AHI (54.4 ± 26.3 vs. 35.6 ± 20.1 events/h; p<0.001)
Results
The association between reduced REM sleep and mortality was independent of OSA severity as measured by the apnea-hypopnea index.
Further adjustment for baseline AHI and a REM-AHI interaction term did not alter the association
The reduced REM group had a substantially higher AHI (54.4 ± 26.3 vs. 35.6 ± 20.1 events/h), yet REM sleep remained an independent predictor beyond AHI
CPAP allocation was also included as a covariate in the primary adjusted model
Methods
The study population consisted of revascularized CAD patients with moderate-to-severe OSA, representing a high-risk cardiovascular cohort.
All participants had an AHI ≥15 events/h and total sleep time ≥240 min on baseline polysomnography
Participants had undergone coronary revascularization prior to enrollment in the RICCADSA trial
Comorbidities including coronary bypass surgery and atrial fibrillation were accounted for in multivariable models
The sample comprised 356 participants drawn from the RICCADSA trial
What This Means
This research examined whether getting too little REM (rapid-eye movement) sleep — the stage associated with dreaming — is linked to a higher risk of dying in people who have both heart disease and a common breathing disorder during sleep called obstructive sleep apnea (OSA). Using data from 356 patients who had undergone procedures to open blocked heart arteries, the researchers followed participants for nearly five years and compared those with the least REM sleep (the bottom 25%, defined as less than 8.7% of their total sleep time) to those with more REM sleep.
The study found that people with reduced REM sleep were more than twice as likely to die during the follow-up period compared to those with more REM sleep, even after accounting for factors like age, weight, sex, OSA severity, and whether patients used a CPAP machine. The mortality rate was 12.8% in the low-REM group versus 4.4% in the higher-REM group. People with reduced REM sleep also tended to be older, heavier, had more severe sleep apnea, and got less total and deep (slow-wave) sleep overall.
This research suggests that measuring REM sleep during diagnostic sleep studies could help identify heart disease patients who are at particularly high risk of death. Unlike overall sleep duration or OSA severity alone, the amount of REM sleep provided additional predictive information about survival. This raises the possibility that interventions targeting sleep quality — not just breathing abnormalities during sleep — could be important in the care of people with both heart disease and sleep apnea.
Balcan B, Celik Y, Thunström E, Glantz H, Strollo P, Redline S, et al.. (2026). Association of reduced REM sleep with mortality in adults with coronary artery disease and obstructive sleep apnea in the RICCADSA cohort.. Sleep & breathing = Schlaf & Atmung. https://doi.org/10.1007/s11325-026-03614-1