Calculate Social Jet Lag

Difference between sleep midpoint on work days and free days.

Usage

social.jet.lag(sleep_periods, work_days = NULL)

Arguments

sleep_periods

Data frame with in_bed_time, out_bed_time columns

work_days

Optional. Logical vector, date vector, or NULL (uses Mon-Fri default)

Value

List with social jet lag metrics, including MSW/MSF (mid-sleep on work and free days), social_jet_lag_hours (MSF - MSW), the sleep-debt-corrected chronotype MSFsc and corrected social_jet_lag_sc_hours (SJLsc), and the number of work/free nights.

Details

Social jet lag is the discrepancy between social and biological time, computed as MSF - MSW (midpoint on free days minus work days).

MSFsc applies the MCTQ sleep-debt correction (Roenneberg et al. 2012): when free-day sleep exceeds work-day sleep (sleep catch-up), the free-day mid-sleep is adjusted down by half the excess over the weekly average sleep duration, and SJLsc = MSFsc - MSW. These are based on time in bed (the supplied in-bed/out-bed times), not on sleep onset and offset.

Positive values (most common) indicate later sleep timing on free days. Values > 1 hour are associated with increased health risks.

References

Wittmann M, Dinich J, Merrow M, Roenneberg T (2006). “Social jetlag: misalignment of biological and social time.” Chronobiology International, 23(1-2), 497–509. doi:10.1080/07420520500545979 .

Roenneberg T, Allebrandt KV, Merrow M, Vetter C (2012). “Social jetlag and obesity.” Current Biology, 22(10), 939–943. doi:10.1016/j.cub.2012.03.038 .

Roenneberg T, Wirz-Justice A, Merrow M (2003). “Life between clocks: daily temporal patterns of human chronotypes.” Journal of Biological Rhythms, 18(1), 80–90. doi:10.1177/0748730402239679 .