Electrocardiogram-based sleep spectrogram measures of sleep stability and glucose disposal in sleep disordered breathing

Abstract

Study objectives: Sleep disordered breathing (SDB) is independently associated with insulin resistance, glucose intolerance, and type 2 diabetes mellitus. Experimental sleep fragmentation has been shown to impair insulin sensitivity. Conventional electroencephalogram (EEG)-based sleep-quality measures have been inconsistently associated with indices of glucose metabolism. This analysis explored associations between glucose metabolism and an EEG-independent measure of sleep quality, the sleep spectrogram, which maps coupled oscillations of heart-rate variability and electrocardiogram (ECG)-derived respiration. The method allows improved characterization of the quality of stage 2 non-rapid eye movement (NREM) sleep.

Design: Cross-sectional study.

Setting: N/A.

Participants: Nondiabetic subjects with and without SDB (n = 118) underwent the frequently sampled intravenous glucose tolerance test (FSIVGTT) and a full-montage polysomnogram. The sleep spectrogram was generated from ECG collected during polysomnography.

Interventions: N/A.

Measurements and results: Standard polysomnographic stages (stages 1, 2, 3+4, and rapid eye movement [REM]) were not associated with the disposition index (D(I)) derived from the FSIVGTT. In contrast, spectrographic high-frequency coupling (a marker of stable or "effective" sleep) duration was associated with increased, and very-low-frequency coupling (a marker of wake/REM/transitions) associated with reduced D(I). This relationship was noted after adjusting for age, sex, body mass index, slow wave sleep, total sleep time, stage 1, the arousal index, and the apnea-hypopnea index.

Conclusions: ECG-derived sleep-spectrogram measures of sleep quality are associated with alterations in glucose-insulin homeostasis. This alternate mode of estimating sleep quality could improve our understanding of sleep and sleep-breathing effects on glucose metabolism.

Keywords: Disposition index; diabetes mellitus type 2; sleep quality; sleep spectrogram.

Figures

Figure 1

Good-quality sleep on the electrocardiogram-spectrogram. Note that high-frequency coupling (HFC), the upper “mountain range,” occurs more than half the night and in bursts throughout the polysomnographic sleep period (although concentrated in the first half of the night). Note also that switches from lower frequency coupling (LFC) are relatively abrupt. HFC and LFC are also clearly separated in terms of frequency. Very-low-frequency coupling (VLFC) is shown in grey in the lower spectral peaks; the distribution of VLFC is strongly reminiscent of REM-sleep distribution. Time of night is on the horizontal axis, coupling frequency on the vertical axis.

Figure 2

Poor-quality sleep on the electrocardiogram-spectrogram. Note that high-frequency coupling,the upper “mountain range,” is reduced relative to Figure 1. There is an increase in low- and very-low-frequency coupling,relative to Figure 1,across the night. Time of night is on the horizontal axis,coupling frequency on the vertical axis.