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Effect of Ventilation on Physiological Recovery During Midday Naps: A Heart Rate Variability Analysis of Office
Atsushi Yamada1, Naoya Morikawa2, Emi Yuda1,3
1Innovation Center for Semiconductor and Digital Future, Mie University, Tsu 514-0102, Mie, Japan.
Background:
In modern office environments, maintaining adequate air quality is essential for cognitive performance and overall well-being. However, the physiological effects of ventilation (CO2 control) during short daytime breaks, particularly midday naps, remain insufficiently explored. This study aimed to investigate the impact of ventilation on autonomic nervous system (ANS) activity using heart rate variability (HRV) metrics.
Methods:
A crossover experiment was conducted with six office workers (mean age: 28 ± 2 years). Two conditions were compared: Condition A (with ventilation/CO2 control) and Condition B (without ventilation). The experimental protocol consisted of three phases: Phase 1 (desk work, 11:00-12:00), Phase 2 (nap, 12:00-13:00, including a 20-25 min nap), and Phase 3 (post-nap desk work, 13:00-14:00). HRV indices (SDNN, RMSSD, CVRR, LF, HF, and LF/HF) were calculated from 5-min segments within each phase.
Results:
A two-way mixed ANOVA revealed a significant main effect of ventilation on the LF/HF ratio during the post-nap phase (p = 0.0050, η2p = 0.9901), indicating improved autonomic stability upon awakening. Furthermore, a three-way mixed ANOVA (Sex × Order × Condition) showed that pNN50, an index of parasympathetic activity, exhibited significant interactions during the nap phase, including Condition × Sex (p = 0.0092) and the three-way interaction (p = 0.0333). Significant Order effects were also observed for heart rate (HR) across all phases (p < 0.05), suggesting habituation to the experimental environment.
Conclusions:
These findings indicate that ventilation is a critical environmental factor influencing physiological recovery during midday naps. Optimizing air quality may enhance autonomic regulation and improve the restorative effects of short daytime sleep in office settings. These findings should be interpreted as exploratory due to the small sample size (n = 6). While LF/HF was used as an index of autonomic balance, its physiological interpretation remains debated and should be considered with caution.
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