Fig. 4.

Scatter plot of relationship between circadian period and phase angle of entrainment in women and men studied in FD protocols. Phase angle of entrainment refers to the interval between circadian phase (fitted core body temperature minimum or melatonin maximum projected from the entire FD dataset to the beginning of the FD segment) and wake time/lights-on. (Upper) Relationship in all 157 subjects as assessed using circadian phase of the core body temperature minimum; linear regression analysis yields a slope of 3.6 ± 0.5 h. (Lower) Relationship as determined using circadian phase of the melatonin maximum in the subset of 129 subjects in whom melatonin data were available; linear regression analysis yields a slope of 4.6 ± 0.5 h. Filled symbols represent women, and open symbols represent men.