Scientific Paper: Sleep Quality and Cardiopulmonary Responses During Exercise Testing: Exploring Chronotropic and Ventilatory Response Relationship with Sleep Quality in Healthy Adult: A Cross-sectional Study

Objectives
The study aimed to investigate the relationship between sleep quality, as measured by the Pittsburgh Sleep Quality Index (PSQI), and chronotropic and ventilatory responses during cardiopulmonary exercise testing (CPET) in a healthy adult population and to explore group differences between good and poor sleepers.
Design
Thirty-three healthy men completed the PSQI and a graded CPET with breath-by-breath gas analysis. Pearson correlation was used to examine relationships between PSQI and CPET outcomes: chronotropic response (%), tidal volume (VT), minute ventilation (VE), VO₂, VCO₂, expired O₂/CO₂, VE/VO₂, and VE/VCO₂. After accounting for age, height, and weight, the correlation was reassessed. Secondary analyses using a standard cut-off point compared good (PSQI < 5) vs poor sleepers (PSQI ≥5) with independent t-tests.
Results
Participants were predominantly poor sleepers (84.8%; PSQI 7.3 ± 3.2). Higher PSQI correlated with lower chronotropic response (r = –0.35, p = 0.04), lower VT (r = –0.42, p = 0.02), lower expired O₂ (r = –0.46, p = 0.01), and lower expired CO₂ (r = –0.33, p = 0.05). Associations with VE, VO₂, VCO₂, VE/VO₂, and VE/VCO₂ were small and non-significant (p’s > 0.05). When age, height, and weight were controlled for, the attenuated chronotropic response association with PSQI was not significant; however, the PSQI association remained significant for expired O₂ (r = –0.319, p = 0.043), with a trend for VT. In group comparisons, chronotropic response was higher but not significant; good sleepers showed higher VT and greater expired O₂/CO₂ (p’s < 0.05)
Conclusions
Poorer sleep quality was linked to a blunted chronotropic response and attenuated ventilatory response at peak during CPET. However, after controlling for age and anthropometry measures, only expired O2 remained linked. Additionally, routine sleep quality screening may add interpretive value to CPET by flagging individuals with reduced ventilatory depth, warranting prospective studies to test whether improving sleep can enhance exercise responses.
Research Study with Best Paper Award Abstract

Background:
Sleep quality is increasingly recognized as a determinant of cardiometabolic and autonomic health, yet its influence on physiological responses during exercise in healthy adults remains poorly understood. While previous work has linked poor sleep to altered autonomic modulation at rest and during recovery, evidence describing how subjective sleep quality affects chronotropic and ventilatory responses during cardiopulmonary exercise testing (CPET) is limited. Understanding these relationships may reveal early subclinical patterns of autonomic and ventilatory dysregulation relevant to exercise tolerance, cardiovascular risk, and rehabilitation.

Objective:
This study aimed to investigate the association between subjective sleep quality, assessed using the Pittsburgh Sleep Quality Index (PSQI), and both chronotropic and ventilatory responses during CPET in healthy adults. A secondary objective was to compare cardiopulmonary responses between good and poor sleepers to identify physiologically meaningful group differences.

Methods:
Thirty-three healthy adult men completed the PSQI and underwent a standardized graded treadmill CPET with breath-by-breath gas analysis. Chronotropic response (CR%), tidal volume (VT), ventilatory output (VE), oxygen uptake (VO₂), carbon dioxide output (VCO₂), ventilatory equivalents (VE/VO₂, VE/VCO₂), and expired O₂/CO₂ volumes were recorded at peak exercise. Pearson correlations evaluated associations between PSQI and physiological variables, with additional partial correlations adjusting for age, height, and weight. Independent t-tests compared CPET responses between good sleepers (PSQI < 5) and poor sleepers (PSQI ≥5). Statistical significance was set at p ≤ 0.05.

Results:
Most participants were classified as poor sleepers (84.8%; mean PSQI 7.3 ± 3.2). Higher (worse) PSQI scores showed significant inverse correlations with chronotropic response (r = –0.35, p = 0.04), tidal volume (r = –0.42, p = 0.02), expired oxygen (r = –0.46, p = 0.01), and expired carbon dioxide (r = –0.33, p = 0.05). No significant associations were found with VE, VO₂, VCO₂, or ventilatory equivalents. After adjusting for age and anthropometric variables, the relationship with chronotropic response became non-significant, but the association with expired O₂ remained significant (r = –0.32, p = 0.04), suggesting a robust link between sleep quality and ventilatory depth.
Group comparisons showed that good sleepers exhibited higher tidal volume (p = 0.02), greater expired O₂ (p = 0.02), and greater expired CO₂ (p = 0.03). Although chronotropic response was higher in good sleepers, the difference did not reach significance. Other ventilatory parameters remained similar across groups.

Conclusion:
Poor subjective sleep quality is associated with attenuated ventilatory response and a blunted autonomic (chronotropic) response during peak exercise in healthy adults. Ventilatory depth—reflected by tidal volume and expired gas volumes—appears particularly sensitive to variations in sleep quality. These findings suggest that even in non-clinical populations, disturbances in sleep may influence physiological performance during CPET by altering chemoreflex-ventilatory integration and autonomic responsiveness.

Novel Contribution:
This study is the first to demonstrate a relationship between PSQI-defined sleep quality and ventilatory responses during CPET in healthy adults, extending previous work focused primarily on autonomic or clinical populations. The identification of reduced tidal volume and diminished expired gases among poor sleepers highlights a novel physiological pathway linking subjective sleep quality to ventilatory efficiency. These results reinforce the importance of incorporating sleep assessment into exercise testing and may have implications for early detection of subclinical autonomic-ventilatory dysfunction.

Implications for Practice and Research:
Routine screening of sleep quality during CPET may enhance test interpretation by identifying individuals with reduced ventilatory depth. Integrating sleep education, behavioral sleep interventions, or targeted respiratory training may help optimize exercise performance and autonomic balance. Future longitudinal and interventional studies should investigate whether improving sleep quality causally enhances chronotropic and ventilatory responses.