Figure 4. Relationship between phase shift and the difference between delay and advance light in the 90 deg either side of acrophase time at baseline, first night shift (N1), second night shift (N2), third night shift (N3), fourth night shift (N4) and averaged over all night shifts (Mean Night).

Negative phase shift indicates phase delay; positive phase shift indicates phase advance. Negative lux difference indicates a greater amount of delaying light (90 deg before acrophase), while positive lux difference indicates a greater amount of advancing light exposure (90 deg after acrophase) compared to delaying. Men are represented as closed triangles, women as open circles.