Sleep-Wake Survival Dynamics in People with Insomnia

Figures & data

Figure 1 Conceptualization of the survival curve analysis.

Notes: Please note that this figure is fictional and does not represent real data. Step 1 depicts a schematic example of sleep and wake over time. Only one sleep cycle is depicted. During step 2, all fragments of NREM sleep are listed and sorted based on their length. Fragments of NREM sleep are assumed to be terminated if they are followed by either wake or REM sleep. In step 3, NREM fragments shorter than 1 minute are excluded from the analysis. At the right, the resulting survival function is plotted. The survival rate represents the percentage of NREM fragments longer than a certain length, e.g. after 1 minute, three out of five (60%) of the sleep fragments is still left (ie, “has survived”), and after 5 minutes only one sleep fragment (20%) is left. In other words, only 20% of the sleep fragments is longer than 5 minutes. In reality, there are multiple sleep cycles, and thus more sleep fragments. Survival curves of REM sleep and wake were calculated using a similar approach. Reprinted under a Creative Commons Attribution 4.0 International License from: Hermans LWA, Regis M, Fonseca P, et al. Assessing sleep-wake survival dynamics in relation to sleep quality in a placebo-controlled pharmacological intervention study with people with insomnia and healthy controls. Psychopharmacology. 2020;238:81–94.¹⁵

Table 1. Descriptive Statistics of Participants

Descriptive Statistics	Insomnia (n=86)	Healthy People (n=94)	Statistical Test
Age (years)	Median 47.0 ± IQR 19.0	Median 35.9 ± IQR 26.3	Wilcoxon W=5759, p<0.001
Sex (n females, n males)	57 females, 29 males	59 females, 35 males
ISI	Mean 21.0 ± SD 3.7 (12–28)	Mean 1.8 ± SD 1.4 (0–6)	t-test t=47, p<0.001
Objective TST (minutes)	Median 389 ± IQR 75 (92–533)	Median 440 ± IQR 57 (229–511)	Wilcoxon W=2043, p<0.001
Objective SOL (minutes)	Median 17 ± IQR 26 (1–157)	Median 7 IQR 8 (1–67)	Wilcoxon W=5645, p<0.001
Objective WASO (minutes)	Median 68 ± IQR 60 (8–292)	Median 47 ± IQR 44 (8–260)	Wilcoxon W=5336, p<0.001
Subjective TST (minutes)	Median 233 ± IQR 176 (0–465)	Median 420 ± IQR 60 (180–510)	Wilcoxon W=841, p<0.001
#Awakenings	Median 27 ± IQR 16 (8–59)	Median 20 ± IQR 10 (8–45)	Wilcoxon W=5686, p<0.001

Note: Text in bold indicates statistical significance.

Table 2. Frequency (Percentage) of Co-Morbidities Within the Insomnia Group

Co-Morbidities	# (%)
Depression and/or anxiety	13 (15.1)
ADHD	2 (2.3)
Other psychiatric diagnosis	7 (8.1)
PLM^a index >15	4 (4.7)
Mild OSA: 4 < AHI <15	2 (2.3)

Note: ^aThe total number of periodic leg movements per hour of total sleep time.

Table 3. Results of Sleep and Wake Survival Analysis

	Intercept, Adjusted R-Squared	Group (Healthy/Insomnia)	Age (Years)	Sex (Male/Female)	TST (Hours)	Group*Age	Group*Sex	Age*Sex	Group*TST	Age*TST	Sex*TST
NREM scale, ʎ	B=6.7 R^2=0.34	B=–0.82	B=0.17	B=−1.2	B=−0.03	X	X	B=0.18	B=−0.86	B=−0.31	X
		t=−3.1	t=0.78	t=−4.9	t=−0.16			t=0.69	t=−2.5	t=−2.2
		p=0.0026	p=0.44	p<0.0001	p=0.87			p=0.49	p=0.012	p=0.028
NREM shape	B=0.85 R^2=0.06	B=−0.048	B=0.012	B=0.050	B=0.013	B=0.023	B=0.081	X	B=0.037	X	X
		t=−1.4	t=0.74	t=0.17	t=0.92	t=1.1	t=2.0		t=1.52
		p=0.17	p=0.46	p=0.87	p=0.36	p=0.29	p=0.051		p=0.13
REM scale, ʎ	B=8.0 R^2=0.17	B=−1.3	B=−0.28	B=−1.3	B=−0.61	X	X	X	B=−0.72	B=−0.66	X
		t=−2.3	t=−1.0	t=−2.5	t=−1.4				t=−0.98	t=−2.4
		p=0.023	p=0.31	p=0.012	p=0.16				p=0.33	p=0.020
REM shape	B=1.6 R^2=0.00	B=0.084	X	X	X	X	X	X	X	X	X
		t=0.77
		p=0.44
Wake scale, ʎ	B=31 R^2=0.21	B=7.8	B=−3.4	X	Not assessed	B=−6.3	X	X	Not assessed	Not assessed	Not assessed
		t=2.8	t=−1.7			t=−2.2
		p=0.0061	p=0.10			p=0.028
Wake shape	B=0.88 R^2=0.17	B=0.21	B=−0.058	B=−0.055	Not assessed	B=−0.16	X	X	Not assessed	Not assessed	Not assessed
		t=2.8	t=−1.1	t=−0.77		t=−2.2
		p=0.0050	p=0.28	p=0.45		p=0.030

Notes: Asterisks (*) indicate interaction effects. For wake survival parameters, we did not incorporate TST in the analysis. Text in bold indicates statistical significance.

Abbreviations: B, unstandardized effect size; X, parameter for which the lasso algorithm determined a coefficient of zero.

Table 4. Results of Sensitivity Analysis of Wake Parameters, Including Only Participants Older Than 29

	Intercept, Adjusted R-Squared	Group (Healthy/Insomnia)	Age (Years)	Sex (Male/Female)	TST (Hours)	Group*Age	Group*Sex	Age*Sex	Group*TST	Age*TST	Sex*TST
Wake scale, ʎ	B=32 R^2=0.07	B=4.7	B=−4.3	X	Not assessed	B=−1.8	X	X	Not assessed	Not assessed	Not assessed
		t=1.6	t=−2.1			t=−0.46
		p=0.12	p=0.040			p=0.64
Wake shape	B=0.86 R^2=0.07	B=0.13	B=−0.080	B=0.0098	Not assessed	B=−0.019	X	X	Not assessed	Not assessed	Not assessed
		t=2.1	t=−1.9	t=0.20		t=−0.24
		p=0.039	p=0.054	p=0.84		p=0.81

Notes: Asterisks (*) indicate interaction effects. For wake survival parameters, we did not incorporate TST in the analysis.

Abbreviations: B, unstandardized effect size; X, parameter for which the lasso algorithm determined a coefficient of zero.

Figure 2 Correlations between survival parameters and subjective sleep.

Notes: (A) NREM scale parameter vs wake scale parameter. (B) NREM scale parameter vs wake shape parameter. (C) NREM scale vs Insomnia Severity Index. (D) NREM scale parameter vs subjective total sleep time.

Hermans LWA, Regis M, Fonseca P, et al. Assessing sleep-wake survival dynamics in relation to sleep quality in a pharmacological intervention study. Psychopharmacol. 2021;238:83–94. doi:10.1007/s00213-020-05660-3

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