Genetics Influence Sleep Adaptability in Shift Work and Seasonal Changes

Many individuals experience variations in sleep patterns and mood linked to seasonal shifts, especially in temperate zones where winter often prompts hibernation-like behavior and summer encourages extended activity into the night. Even those closer to the equator are not immune to seasonal influences, as our evolutionary history as seasonal animals suggests. These natural behavioral adjustments are triggered by environmental cues such as light exposure.

Recent research indicates that our ability to adapt to modern lifestyle factors—like rotating shift work and, potentially, jet lag—is also rooted in our genetic makeup. A study involving approximately 3,000 US medical interns wearing health trackers over a year uncovered notable individual differences tied to a specific gene called SLC20A2. The study found that interns’ activity levels and wakefulness varied with the seasons, with some showing greater change than others. Heart rate data helped researchers assess each participant’s internal clock, known as the circadian rhythm, which governs various physiological processes including body temperature and hormone levels.

Findings revealed that those with a significant seasonal fluctuation in their activity levels experienced more disruption when working night shifts during winter, often affecting their sleep-wake cycles. Conversely, these changes were less pronounced or even inverted for summer shifts. The study linked these behaviors to the SLC20A2 gene, which encodes a protein involved in ion transport within neurons, critical for electrical signaling in the brain.

Variants in the SLC20A2 gene, identified as single nucleotide polymorphisms (SNPs), influence how our circadian rhythms respond to changing day lengths. This genetic variation affects individual responses to shift work and may explain why some people tolerate irregular schedules better than others. The findings also highlight that our response to seasonal light changes is mediated by the suprachiasmatic nuclei (SCN), a brain region that coordinates our biological clock based on light signals received through the eyes.

Understanding these genetic and biological factors offers promising pathways to develop personalized strategies for shift workers, improving health outcomes and adaptation to irregular schedules. Additionally, this knowledge can help individuals manage jet lag and seasonal changes more effectively, promoting better sleep and overall well-being.