Willoughby · Sleep 2025 · observational cohort study · n=57240

Insights about travel-related sleep disruption from 1.5 million nights of data.

Cited 13 times in the scientific literature.

Level 3 - non-randomized controlled study

Observational longitudinal cohort study analyzing consumer wearable data before and after travel events.

PubMed 40127035 · doi:10.1093/sleep/zsaf077 · record verified 2026-08-28

What was done

Researchers analyzed de-identified objective sleep tracking data from 57,240 Oura Ring users across 64,847 trips (totaling ~1.5 million nights of data). Trips were at least 1,000 km in distance and originated from North America or Europe. Sleep timing, duration, and macro-architecture were tracked over a 30-day window (15 days before and 15 days after travel) and evaluated based on travel direction, number of time zones crossed, and baseline sleep habits.

What was found

Sleep loss began the night before travel due to early awakening. Sleep duration dropped during and immediately after travel but returned to within ~12 minutes of baseline after ~2 days. Conversely, sleep timing and sleep macro-architecture took much longer to normalize; sleep timing did not return to baseline even after 15 days. Sleep disruption was more severe with eastward travel and with a greater number of time zones crossed. Interindividual variability in sleep duration and timing diminished during travel.

Why it matters

This large-scale real-world dataset reveals a clear dissociation between homeostatic sleep recovery (duration normalizes in ~2 days) and circadian realignment (timing remains shifted past two weeks), providing empirical benchmarks for post-travel recovery outside controlled laboratory conditions.

Limits

The sample was restricted to users of a specific commercial smart ring from North America and Europe, introducing socioeconomic and geographic selection bias. The abstract does not report specific values for sleep architecture metrics, nor does it control for travel purpose, light exposure, travel mode, jet lag interventions, or substance use (such as caffeine, alcohol, or sleep aids).

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