Lying Awake at Night: Cardiac Autonomic Activity in Relation to Sleep Onset and Maintenance

Figure 1. Heart rate variability (HRV) feature extraction by using a sliding windows of 2.5 min centered on each 30-s epoch. The boxes with the darker or lighter color represent the central epoch and the grayscale corresponds to the color of the window name, e.g., the 4th epoch from the left corresponds to the central epoch of window 2.

Figure 2. (Left) Relation between wake after sleep onset duration (WASO) and sleep onset latency (SOL) as measured by Spearman's correlation, r = −0.001, p = 0.97. (Right) Relation between WASO and age as measured by Spearman's correlation, r = 0.55, p < 0.0001.

Figure 3. (Left) LFnu in the first 10 min in bed intending to sleep between short and long SOL for all age groups as measured by GLM model, χ2 = 3.71, p = 0.05. (Right) HFnu in the first 10 min in bed intending to sleep between short and long SOL for all age groups as measured by GLM model, χ2 = 5.46, p < 0.05. n, number of participants in the SOL group for the specific age group (bold for the long SOL group). a.u., arbitrary unit.

Figure 4. (Left) LF/HF in the first 10 min in bed intending to sleep between short and long SOL for all age groups as measured by GLM model, χ2 = 1.93, p = 0.17. (Right) HFfreq in the first 10 min in bed intending to sleep between short and long SOL for all age groups as measured by GLM model, χ2 = 3.3, p = 0.07. n, number of participants in the SOL group for the specific age group (bold for the long SOL group). a.u., arbitrary unit.

Figure 5. (Left) LFnu 10 min before sleep onset between short and long SOL for all age groups as measured by GLM model, χ2 = 2.76, p = 0.09. (Right) HFnu 10 min before sleep onset between short and long SOL for all age groups as measured by GLM model, χ2 = 3.88, p < 0.05. n, number of participants in the SOL group for the specific age group (bold for the long SOL group). a.u., arbitrary unit.

Figure 6. (Left) LFnu 10 min after sleep onset between short and long SOL for all age groups as measured by GLM model, χ2 = 3.88, p < 0.05. (Right) HFnu 10 min after sleep onset between short and long SOL for all age groups as measured by GLM model, χ2 = 4.10, p < 0.05. n, number of participants in the SOL group for the specific age group (bold for the long SOL group). a.u., arbitrary unit.

Figure 7. (Left) LFnu 10 min after sleep onset between short and long WASO groups for a cutoff of 30 min for all age groups as measured by GLM model, χ2 = 3.40, p = 0.07. (Right) HFnu 10 min after sleep onset between short and long WASO groups for a cutoff of 30 min for all age groups as measured by GLM model, χ2 = 4.37, p < 0.05. n, number of participants in the SOL group for the specific age group (bold for the long WASO group). a.u., arbitrary unit.

Figure 8. (Left) LFnu 10 min after sleep onset between the short and the long WASO group for a cutoff of 66 min for all age groups as measured by GLM model, χ2 = 11.92, p < 0.001. (Right) HFnu 10 min after sleep onset between the short and the long WASO group for a cutoff of 66 min for all age groups as measured by GLM model, χ2 = 8.27, p < 0.005. n, number of participants in the WASO group for the specific age group (bold for the long WASO group). a.u., arbitrary unit.

Figure 9. (Left) LFnu 10 min after sleep onset between the short and the long WASO group for a cutoff of 66 min for all BMI groups as measured by GLM model, χ2 = 11.92, p < 0.001. (Right) HFnu 10 min after sleep onset between the short and the long WASO group for a cutoff of 66 min for all BMI groups as measured by GLM model, χ2 = 8.27, p < 0.005. n, number of participants in the WASO group for the specific age group (bold for the long WASO group). a.u., arbitrary unit.

Figure 10. (Left) LFnu 10 min after sleep onset between the short and the long WASO group for a cutoff of 66 min for female and men as measured by GLM model, χ2 = 11.92, p < 0.001. (Right) HFnu 10 min after sleep onset between the short and the long WASO group for a cutoff of 66 min for female and male as measured by GLM model, χ2 = 8.27, p < 0.005. n, number of participants in the WASO group for the specific age group (bold for the long WASO group). a.u., arbitrary unit.