Rhythm scrambling: good, bad or indifferent?

The scrambling of rhythms, i.e. their mixing-up or throwing into disorder, on a variety of schedules of lighting and feeding, left the average overall life span of several groups of mice unaffected. One particularly scrambled schedule prolonged 10th-decile survival time. The phase-shifting of rhythms, in a mammalian simulation of shift-work schedules, need not be harmful and can be indifferent or even beneficial. Such findings have important implications for health, performance and safety in human shift-work by both sexes and for the choice of other schedules, such as those for drug treatments or exercise.