Irregular sleep duration was associated with reduced exercise capacity in CAD patients, with a shorter 6-minute walk distance compared to regular sleep (338.8 vs 406.2 meters; p=0.045).
Cross-Sectional (n=28)
No
Does irregular sleep duration reduce exercise capacity in patients with coronary artery disease undergoing cardiac rehabilitation?
Increased day-to-day fluctuation in sleep duration is associated with significantly reduced exercise capacity in patients with coronary artery disease entering cardiac rehabilitation.
Effect estimate: Beta -14.4 meters per 10-minute increase in sleep variability (95% CI -28.1, -0.7)
Absolute Event Rate: 338.8% vs 406.2%
p-value: p=0.041
Background: Sleep regularity is emerging as an independent determinant of health. Multiple studies suggest a link between increased variability in sleep duration and timing and adverse cardiovascular, metabolic, and cognitive outcomes. There is, however, a lack of data on the implications of sleep regularity for aerobic capacity and physical endurance, particularly in patients with established cardiovascular disease. This study seeks to investigate the influence of irregularity in sleep duration on functional capacity in patients with coronary artery disease (CAD) undergoing cardiac rehabilitation (CR). Methods: We recruited a sample of patients with CAD who were referred to CR at Mayo Clinic Rochester. Participants completed a 6-minute walk test (6MWT) upon enrollment into CR. 6MWT variables included distance walked (meters), predicted distance walked (percentage) and estimated metabolic equivalents (METs). 24-hour objective sleep quality and quantity were assessed over a 7-day period by wrist actigraphy. Average standard deviation (SD) of sleep duration was used to define sleep regularity, with SD >60 minutes indicating irregular sleep. Chi-square test, independent samples t-test, and linear regression were used for statistical analysis. Results: Twenty-eight participants with valid actigraphy and 6MWT were included in this analysis (eight females; mean age 67.4 ± 11.6 years; body mass index 31.1 ± 5.8 kg/m 2 ). The average total sleep time was 7.1 ± 1.2 hours, and 10 participants (35.7%) exhibited sleep duration SD >60 minutes. Demographic, clinical and sleep characteristics were comparable between the regular and irregular sleep groups. Compared to patients with regular sleep, those with irregular sleep had poorer 6MWT, with shorter distance walked (406.2 ± 81.2 meters vs 338.8 ± 80.7 meters; p = 0.045), lower % of predicted distance walked (87.1 ± 18.7% vs 69.2 ± 11.4%; p = 0.011), and lower METS (2.99 ± 0.36 vs 2.63 ± 0.38; p = 0.022). Irregular sleep remained significantly associated with performance at the 6MWT after taking into account age and sex, with patients walking 14.4 meters fewer with every 10-minute increase in sleep variability (95% CI -28.1, -0.7; p 0.041). Conclusions: Increased day-to-day fluctuation in sleep duration is associated with reduced exercise capacity in patients with CAD undergoing CR. These findings add to the mounting body of evidence linking irregular sleep patterns to heightened cardiovascular risk, and support the integration of sleep monitoring in the CR practice to enhance risk stratification and outcome prediction. Funding Source: Sleep Number Corp. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Makarla et al. (Fri,) conducted a cross-sectional in Coronary artery disease (CAD) (n=28). Irregular sleep (sleep duration SD >60 minutes) vs. Regular sleep was evaluated on 6-minute walk test (6MWT) distance walked in meters (Beta -14.4 meters per 10-minute increase in sleep variability, 95% CI -28.1, -0.7, p=0.041). Irregular sleep duration was associated with reduced exercise capacity in CAD patients, with a shorter 6-minute walk distance compared to regular sleep (338.8 vs 406.2 meters; p=0.045).