Table 1. Circadian phase shift responses to light (h ± SEM).

Physiologic measure	Continuous red light	Intermittent red light	Bright white light
Salivary melatonin	−0.68±0.54	−0.80±0.37	−2.83±0.29*†
Salivary cortisol	−1.55±0.45	−0.54±0.55	−2.69±0.66 †
Core body temperature	−1.24±0.48	−0.48±0.38	−2.82±0.32*†
Forehead skin temperature	−0.33±0.41	−0.37±0.33	−2.10±0.45*†
Heart rate	−0.41±0.45	−1.23±0.88	−2.53±0.47*

Circadian phase shift responses are shown for 6 h of exposure to continuous red light, intermittent red light and darkness, or bright white light near the onset of melatonin secretion. By convention, negative values indicate phase delay shifts. Using a linear mixed-effects model for comparing phase resetting responses, bright white light elicited a larger response than either red light condition (P<0.003). Phase shifts were similar in response to continuous versus intermittent red light (P = 0.69), and did not differ across physiologic measures (P = 0.35). Data were also analyzed using one-way ANOVA, whereby asterisks (*) indicate significant differences in response to bright white light versus continuous red light, and daggers (^†) indicate significant differences in response to bright white light versus intermittent red light. Phase resetting did not differ between red light conditions.