0150 Afternoon Napping Does Not Impact Autonomic Function in Healthy Adults

Abstract

Abstract Introduction Proper overnight sleep is important for autonomic nervous system function. However, less is known about the effects of daytime napping on wake autonomic regulation. In the present study, we assessed autonomic function following a daytime nap. We hypothesized that a 90-minute afternoon nap would significantly improve wake heart rate variability (HRV) and blood pressure (BP). Methods Fourteen participants (7 female, 24±1 years, 24 ±1 kg/m2) took part in the study. Subjects completed an autonomic function test after no nap (control condition) or a 90-minute nap opportunity (nap condition) on separate days using a randomized, crossover design. During the autonomic test, participants were fitted with three-lead electrocardiography (ECG), continuous beat-to-beat blood pressure (Finapres NOVA, Netherlands), and respiratory monitoring (pneumobelt). The autonomic function test consisted of 5-minutes of spontaneous breathing, 5-minutes of controlled breathing (15 breaths/min), and a 2-minute cold pressor test (CPT). Frequency-domain HRV in the low (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) components were determined via Fast Fourier transformation. Time-domain HRV was quantified using RMSSD and pNN50. Paired sample t-tests were completed between the control and nap sessions. Results Mean total sleep time (TST) for the nap session was 74±5 minutes. Contrary to our hypothesis, an afternoon nap did not change wake heart rate (HR, Control: 70±3 vs. Nap: 68±3 bpm, p = .31) or mean arterial pressure (MAP, Control: 77±3 vs. Nap: 83±3 mmHg, p = 0.70). Similarly, no differences were observed in HF (Control: 2632±628 vs. Nap: 2150±494 ms2, p = .33), LF (Control: 1702±373 vs. Nap: 1345±257 ms2, p = .20), or LF/HF (Control: 92±16 vs. Nap: 92±17%, p = .97) between conditions. RMSSD (Control: 82±12 vs. Nap: 79±11 ms, p = .723) and pNN50 (Control: 43±6 vs. Nap: 47±6%, p = .30) were not impacted by a daytime nap. Lastly, changes in HR (Control: ∆14±3 vs Nap: ∆18±3 bpm, p = .114) and MAP (Control: ∆23±4 vs. ∆Nap: 27±4 mmHg, p = .28) during CPT were not different between conditions. Conclusion An afternoon nap does not appear to significantly influence autonomic function at rest or during CPT in young healthy adults. Support (If Any)