CLOCK Genotype Modulates Associations Between Blue Light Exposure and Circadian Activity Amplitude

May 14, 2026Physiology & behavior

CLOCK gene type may change how blue light affects daily activity rhythms

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Abstract

116 adults were assessed for how the CLOCK rs1801260 polymorphism influences physical activity rhythms in relation to light exposure and prior COVID-19 infection.

Poor light hygiene, indicated by a Normalized Amplitude of Blue Light Exposure (NA BLE) less than 1, was associated with delayed physical activity timing and decreased amplitude.
CLOCK rs1801260 TT homozygotes with NA BLE less than 1 exhibited a significant decrease in both absolute (p=0.032) and normalized (p=0.003) physical activity amplitude.
Compared to C-carriers, CLOCK rs1801260 TT genotype carriers with poor light hygiene had a reduced physical activity amplitude (β = -0.483, p = 0.017).
TT carriers who also had a history of COVID-19 demonstrated an even greater reduction in physical activity amplitude compared to C carriers without such a history (p=0.036).
The findings suggest a combined effect of genetic factors, environmental influences, and previous illness on disruptions in circadian rhythms.

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BACKGROUND: Circadian disruption is linked to adverse health outcomes, but individual susceptibility to light-based timing signals remains unclear. This study assessed how the CLOCK rs1801260 polymorphism modulates the impact of dynamic light exposure and prior SARS-CoV-2 infection on objective physical activity (PA) rhythmicity.

METHODS: 116 adults (75 COVID+) underwent 7-day wrist actigraphy with blue light recording (Tyumen, Russia, 57°N). Cosinor-derived PA parameters (MESOR, amplitude [A], A/M ratio, acrophase) and non-parametric indices assessed rhythmicity. Regression/ANCOVA examined NA_BLE × CLOCK TT vs non-TT × COVID status interactions, controlling for age/sex/BMI.

RESULTS: Poor light hygiene (Normalized Amplitude of Blue Light Exposure, NA BLE <1) delayed the acrophase and reduced PA amplitude. Specifically, CLOCK rs1801260 TT homozygotes with NA BLE<1 had a reduced absolute (p=0.032) and normalized (p=0.003) PA amplitude. CLOCK rs1801260 TT genotype with NA BLE<1 exhibited reduced PA amplitude compared to C-carriers (β = -0.483, p = 0.017, η² = 0.201) after adjusting for age, sex, and COVID-19 status. A compounding negative effect was noted in TT carriers with both NA BLE<1 and COVID-19 history, showing an even smaller PA amplitude than C carriers with no history of COVID-19 (p=0.036).

CONCLUSION: These findings reveal a triple-hit model where genetic susceptibility (CLOCK TT), environmental insult (poor light hygiene), and prior systemic illness (COVID-19) synergistically disrupt circadian activity rhythms. They underscore the need for personalized chronotherapy integrating genetic profiling and post-viral health status.

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CLOCK Genotype Modulates Associations Between Blue Light Exposure and Circadian Activity Amplitude

Abstract

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