Sleep phase, duration, and the frequency/timing of sleep sessions from typical shift schedules.

Values represent mean ± SEM for two age groups (≤36 and>36). Adj – adjusted for sleep debt (see Methods).*Significantly different from younger night-shift nurses, Kruskal Wallis χ2(3) = 20.5, Tamhane's posthoc, p**Significant main effect of age: adjusted midsleep on freedays, Scheirer-Ray-Hare extension of the Kruskal Wallis test, H(1) = 33.0, ppp†Significantly different from day-shift nurses, regardless of age: adjusted midsleep on freedays, Scheirer-Ray-Hare extension of the Kruskal Wallis test, H(1) = 45.4, ppp