Leptin Associates with Circadian Light Hygiene and REV-ERBα in Arctic Residents

Leptin regulates metabolism and is modulated by circadian rhythms and light exposure, which is of fundamental importance for Arctic residents living under conditions of extreme photoperiods. This longitudinal study aimed to investigate the association between morning leptin, seasonal circadian light hygiene, and NR1D1 expression in 64 Arctic residents (aged 18‑54 years; 88.7% women) using 7‑day actigraphy, morning leptin and NR1D1 expression. Better circadian light hygiene, measured as normalized blue light exposure amplitude (NA BLE) was associated with lower morning leptin (β = -0.263; p < 0.001), also after adjusting for photoperiod. This association remained significant after controlling for sex, age, and ethnicity (β = -0.171). Later BLE light onset also predicted elevated leptin (β = 0.162; p = 0.031). In non-natives exclusively, reduced NR1D1 expression correlated with higher leptin (β = -0.276; p = 0.026).