Insights into vascular physiology from sleep photoplethysmography

Gizem Yilmaz; Ju Lynn Ong; Lieng-Hsi Ling; Michael W L Chee

doi:10.1093/sleep/zsad172

Insights into vascular physiology from sleep photoplethysmography

Sleep. 2023 Oct 11;46(10):zsad172. doi: 10.1093/sleep/zsad172.

Authors

Gizem Yilmaz¹, Ju Lynn Ong¹, Lieng-Hsi Ling^{2

3}, Michael W L Chee¹

Affiliations

¹ Centre for Sleep and Cognition, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
² Department of Cardiology, National University Heart Centre, National University Health System, Singapore and.
³ Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.

Abstract

Study objectives: Photoplethysmography (PPG) in consumer sleep trackers is now widely available and used to assess heart rate variability (HRV) for sleep staging. However, PPG waveform changes during sleep can also inform about vascular elasticity in healthy persons who constitute a majority of users. To assess its potential value, we traced the evolution of PPG pulse waveform during sleep alongside measurements of HRV and blood pressure (BP).

Methods: Seventy-eight healthy adults (50% male, median [IQR range] age: 29.5 [23.0, 43.8]) underwent overnight polysomnography (PSG) with fingertip PPG, ambulatory blood pressure monitoring, and electrocardiography (ECG). Selected PPG features that reflect arterial stiffness: systolic to diastolic distance (∆T_norm), normalized rising slope (Rslope) and normalized reflection index (RI) were derived using a custom-built algorithm. Pulse arrival time (PAT) was calculated using ECG and PPG signals. The effect of sleep stage on these measures of arterial elasticity and how this pattern of sleep stage evolution differed with participant age were investigated.

Results: BP, heart rate (HR) and PAT were reduced with deeper non-REM sleep but these changes were unaffected by the age range tested. After adjusting for lowered HR, ∆T_norm, Rslope, and RI showed significant effects of sleep stage, whereby deeper sleep was associated with lower arterial stiffness. Age was significantly correlated with the amount of sleep-related change in ∆T_norm, Rslope, and RI, and remained a significant predictor of RI after adjustment for sex, body mass index, office BP, and sleep efficiency.

Conclusions: The current findings indicate that the magnitude of sleep-related change in PPG waveform can provide useful information about vascular elasticity and age effects on this in healthy adults.

Keywords: arterial stiffness; autonomic nervous system; blood pressure; heart rate variability; photoplethysmography; sleep/wake physiology; vascular health.

Abstract

Grants and funding