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Population-Specific Circadian Drivers and MTNR1B Predict Arctic Morning Cortisol.

Denis Gubin1,2,3, Sergey Kolomeichuk4,5,6, Konstantin Danilenko1,7

  • 1Laboratory for Chronobiology and Chronomedicine, Research Institute of Biomedicine and Biomedical Technologies, Medical University, Tyumen, Russia.

American Journal of Human Biology : the Official Journal of the Human Biology Council
|April 15, 2026
PubMed
Summary

Cortisol levels in Arctic residents are influenced by the timing of daily activities and light exposure. Genetic factors, specifically the MTNR1B polymorphism, also play a role in modulating these cortisol responses.

Keywords:
MTNR1BArcticactigraphycircadiancortisollightphysical activityrs10830963seasons

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Area of Science:

  • Chronobiology
  • Human Physiology
  • Arctic Research

Background:

  • The Hypothalamic-Pituitary-Adrenal (HPA) axis, regulated by cortisol, is sensitive to environmental cues.
  • Circadian rhythms are crucial for physiological regulation and can be disrupted by extreme environments like the Arctic.
  • The MTNR1B gene polymorphism (rs10830963) has been linked to metabolic and circadian phenotypes.

Purpose of the Study:

  • To investigate the relationship between morning cortisol concentration and the circadian timing of physical activity, light exposure, and sleep in Arctic residents.
  • To examine the influence of the MTNR1B rs10830963 polymorphism on this relationship.
  • To explore population-specific differences (Indigenous vs. Non-Indigenous) in these associations.

Main Methods:

  • 7-day actigraphy with RGB light sensors was used to derive circadian parameters.
  • Cortisol levels and actigraphy data were collected longitudinally across different seasons (winter solstice, summer solstice, spring equinox).
  • Statistical analyses included correlation, regression, and two-way ANOVA, stratified by indigeneity and adjusting for relevant covariates.

Main Results:

  • Later timing of physical activity, light exposure, and bedtime were significantly associated with higher morning cortisol concentrations.
  • Non-Indigenous participants were primarily influenced by light exposure timing, while Indigenous participants showed associations with activity and sleep timing.
  • The MTNR1B rs10830963 genotype modulated cortisol levels, with G-allele carriers exhibiting lower concentrations.

Conclusions:

  • Cortisol in Arctic residents is linked to circadian behavior timing, with distinct drivers for Indigenous and Non-Indigenous populations.
  • Non-Indigenous individuals integrate both photic and behavioral cues, whereas the Indigenous population relies more on behavioral rhythms.
  • The MTNR1B polymorphism further modulates cortisol, highlighting the interplay between environmental timing and genetic background in regulating HPA axis activity in extreme photic environments.