Circadian Light Hygiene Is Associated with Anemia Markers in Young Adults

Background: Light exposure (LE) and its influence on circadian rhythms are recognized to impact various physiological domains, yet their specific associations with hematological status, particularly in high-latitude environments, remain underexplored. Understanding these links could offer insights into maintaining hematological health. Methods: This study investigated the relationship between 24 h light exposure (LE), blue light exposure (BLE), sleep, and physical activity (PA) and hematological markers in 85 young adults (18–25 years). Participants underwent simultaneous 7-day monitoring using actigraphy and RGB sensors, coupled with morning blood sampling for hemoglobin (HGB), hematocrit (HCT), mean corpuscular hemoglobin (MCH), and red blood cell distribution width (RDW-CV). Results: Univariate analyses revealed significant correlations: normalized BLE amplitude (NA BLE) positively correlated with HGB (r = 0.369, p = 0.001) and MCH (r = 0.378, p < 0.001). A later BLE acrophase correlated with lower HGB and MCH, but higher RDW-CV. Later PA acrophase was associated with lower MCH and higher RDW-CV, while later bedtime correlated with lower HGB and MCH. Multivariate regressions confirmed that a larger NA BLE predicted higher HGB (β = 0.206, p = 0.037) and MCH (β = 0.377, p < 0.001), and an earlier BLE acrophase predicted higher MCH and smaller RDW-CV. Conclusions: Advantageous circadian patterns of BLE and PA are linked to a favorable hematological status in young adults during the light-deficient fall season at higher latitudes, underscoring the importance of optimizing light and activity timing for hematological health.