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3mo ago

Dual Circadian Clocks and Gene Variants Govern Seasonal Shift Work Adaptation

Based on wearable device data, genetic samples, the study shows heightened seasonal sensitivity can worsen circadian misalignment during winter months.

Now, the U-M team has provided some of the strongest support for the idea yet in observing how that seasonality plays out in a large, real-world study. Credit: Neuroscience News
Kim et al. hypothesize that the vast interindividual differences in shift work adaptation -- critical for shift worker health -- can in part be explained by biological mechanisms for seasonal timing. Image credit: Sasin Tipchai.

Overview

  • Researchers identified two internal clocks—one tracking dawn and the other tracking dusk—that jointly regulate human circadian rhythms.
  • Analysis of wearable data from over 3,000 medical interns revealed peak physical activity in summer and greater sleep–heart rate misalignment in winter.
  • Multiple SLC20A2 gene polymorphisms were linked to significant seasonal differences in sleep duration, activity levels and circadian entrainment.
  • A mathematical model of neuronal coupling in the suprachiasmatic nucleus explained why some individuals entrain faster yet endure greater misalignment under irregular schedules.
  • Findings could guide personalized shift scheduling and interventions for seasonal affective disorder and other circadian-related health conditions.