A novel method to separate circadian from non-circadian masking effects to enhance estimation of circadian timing and amplitude from core body temperature.
Level 4 - case-series / case-control
Analytic method validation study in a single controlled laboratory cohort with within-subject comparison
PubMed 40339518 · doi:10.1016/j.sleep.2025.106530
What was done
Researchers evaluated a physiology-grounded generalized additive model designed to separate circadian from non-circadian influences (such as sleep, wake, and activity) on core body temperature (CBT). The model was tested on continuous CBT data collected via ingestible capsules at 30-second intervals from 33 healthy adults (mean age 32 ± 13 years) during a 39-hour in-laboratory protocol consisting of an overnight sleep period followed by extended wakefulness. Performance in estimating the circadian core temperature minimum (Tmin) was compared against standard cosine-fitting methods.
What was found
The generalized additive model demonstrated better fit to CBT data compared to the traditional cosine model (Pearson R = 0.90 [95% CI: 0.83-0.96] versus 0.81 [95% CI: 0.55-0.93]). The difference between estimated versus measured circadian Tmin, derived from the day without sleep, was 0.2 hours (95% CI: -0.5 to 0.3) for the new method compared to 1.4 hours (95% CI: 1.1 to 1.7) for the traditional cosine method, removing a sleep-related bias toward earlier Tmin estimates.
Why it matters
Masking effects from sleep and activity frequently distort core body temperature analysis, impairing non-invasive circadian phase estimation. This computational demasking approach provides more accurate estimates of circadian timing without requiring prolonged constant routine protocols.
Limits
The dataset was limited to a small sample of 33 healthy participants in a strictly controlled 39-hour laboratory environment. Performance was not tested in free-living conditions, shift workers, clinical populations with circadian rhythm disorders, or over multi-day continuous recordings.
Cited by
- context Human body temperature must increase by approximately 1 to 3 degrees Fahrenheit to wake up feeling energized.
- context Human body temperature must increase by approximately 1 to 3 degrees in order to wake up feeling energized and refreshed.