Table 2.

Results of the GLM model applied to the mean values of each HRV feature during the three time periods of interest between the short and long SOL group.

HRV feature	Main effect	P-value	PS
LFnuwits	group: χ2 = 3.71	p = 0.05	0.54
	age: χ2 = 0.02	p = 0.89
	age x group: χ2 = 2.5	p = 0.11
HFnuwits	group: χ2 = 5.46	p < 0.05	0.48
	age: χ2 = 10.36	p < 0.005
	age x group: χ2 = 5.66	p < 0.05
LF/HFwits	group: χ2 = 1.93	p = 0.17	0.52
	age: χ2 = 4.2	p < 0.05
	age x group: χ2 = 2.43	p = 0.12
HFfreqwits	group: χ2 = 3.3	p = 0.07	0.49
	age: χ2 = 0.17	p = 0.68
	age x group: χ2 = 3.75	p = 0.05
LFnubSO	group: χ2 = 2.76	p = 0.09	0.52
	age: χ2 = 0.01	p = 0.91
	age x group: χ2 = 3.24	p = 0.07
HFnubSO	group: χ2 = 3.88	p < 0.05	0.49
	age: χ2 = 5.64	p < 0.05
	age x group: χ2 = 4.12	p < 0.05
LF/HFbSO	group: χ2 = 1.94	p = 0.16	0.51
	age: χ2 = 2.39	p = 0.12
	age x group: χ2 = 2.20	p = 0.14
HFfreqbSO	group: χ2 = 2.57	p = 0.11	0.51
	age: χ2 = 0.27	p = 0.60
	age x group: χ2 = 3.93	p < 0.05
LFnuaSO	group: χ2 = 3.88	p < 0.05	0.54
	age: χ2 = 0.68	p = 0.41
	age x group: χ2 = 4.21	p < 0.05
HFnuaSO	group: χ2 = 4.10	p < 0.05	0.47
	age: χ2 = 8.27	p < 0.005
	age x group: χ2 = 4.23	p < 0.05
LF/HFaSO	group: χ2 = 2.03	p = 0.15	0.52
	age: χ2 = 2.92	p = 0.09
	age x group: χ2 = 2.37	p = 0.12
HFfreqaSO	group: χ2 = 3.23	p = 0.07	0.47
	age: χ2 = 0.02	p = 0.87
	age x group: χ2 = 2.91	p = 0.09

aSO, 10 min after sleep onset; bSO, 10 min before sleep onset; GLM, generalized linear model; HRV, heart rate variability; wits, the first 10 min in bed with intention to sleep; PS, probability of superiority; SOL, sleep onset latency.