Phase shifts of human circadian rhythms due to shifts of artificial Zeitgebers.
Level 4 - case-series / case-control
Laboratory experimental series in human isolation units without reported randomization or control group
What was done
Human subjects were studied in isolation units under artificial 24-hour Zeitgebers with 6-hour advance and 6-hour delay shifts simulating time zone travel. Researchers monitored re-entrainment rates and patterns across activity, rectal temperature, and psychomotor computation speed.
What was found
The abstract provides directional findings without reporting sample sizes or exact numerical statistics. Activity rhythms re-entrained within several days after both shift types. Rectal temperature rhythms re-entrained more slowly than activity, showing faster re-entrainment after advance shifts than delay shifts. Mean value and amplitude of rectal temperature decreased for several days after advance shifts but not delay shifts. Psychomotor computation speed declined following advance shifts but not delay shifts, re-entraining in parallel with rectal temperature. Duration of re-entrainment correlated with baseline rectal temperature amplitude, and performance decrements correlated with baseline rectal temperature phase.
Why it matters
The study indicates that circadian re-entrainment and transient performance decrements depend on shift direction and may be predictable from pre-shift baseline physiological rhythm characteristics.
Limits
The abstract reports no participant counts, demographics, numerical data, effect sizes, or confidence intervals. Findings from isolated laboratory environments with artificial Zeitgebers may not fully translate to real-world jet lag or shift work settings.
Cited by
- supports It takes nearly two days for the human circadian clock to adjust to a two-hour change in sleep or wake-up time.