Table 2.

Fitted Parameters of Clock Gene Expression for Individual Participants

	BS1 (Baseline)		BS2 (Night shift)		BS3 (Night shift)
	amplitude	Ψwake	amplitude	Ψwake	amplitude	Ψwake
HPER1
T01	*0.298	6.3	*0.132	−1.5	*0.170	0.1
T02	*0.102	−1.0	0.022	8.6	0.103	−10.6
T04	0.063	0.9	0.174	−1.3	*0.232	−2.2
T05	0.040	−9.2	0.124	−1.8	*0.309	−9.6
T06	*0.336	−11.3	*0.218	4.6	—	—
HPER2
T01	0.049	−13.5	*0.257	−1.1	*0.155	0.9
T02	*0.212	1.8	0.083	−2.5	*0.261	−1.3
T04	0.112	−9.8	*0.150	−1.4	*0.188	−2.4
T05	*0.178	−9.1	*0.130	3.8	*0.121	0
T06	*0.227	−9.4	*0.183	6.6	—	—
HBMAL1
T01	*0.105	−11.9	*0.274	−1.3	*0.174	12.0
T02	*0.255	−10.7	*0.230	7.2	*0.248	−2.9
T04	*0.286	−9.9	*0.295	−0.6	*0.272	17.5
T05	*0.122	−9.2	0.130	−0.8	*0.153	10.8
T06	*0.284	−9.3	*0.215	8.2	—	—

Regression analyses were performed on individual profiles of HPER1, HPER2 and HBMAL1 to determine fitted amplitude and circadian phase (time of fitted maximum expression). The relationship between circadian phase of clock gene expression and the sleep/wake cycle is given as a phase angle (Ψ_wake, in hrs) calculated as: [end of the sleep/darkness period – circadian phase of clock gene expression]. Thus, negative phase angles indicate that circadian phase occurred after the end of the sleep/darkness episode. Positive phase angles indicate that circadian phase occurred before the end of the sleep/darkness episode. Three 24-hr blood sampling sessions were performed before the start of simulated night shifts (experimental day 2; BS1), after three days on the night shift work shifted schedule with daytime sleep/darkness (experimental days 5-6; BS2), and at the end of the shifted schedule with daytime sleep/darkness (experimental days 11-12; BS3). Subject T06, did not participate in the final blood sampling session. Statistically significant amplitudes (i.e., 95% confidence interval does not include zero) are indicated with an asterisk (*).