MTNR1B rs10830963 G Genotype Amplifies Blood Lipid Profile Susceptibility to Poor Circadian Light Hygiene in Arctic Residents

Circadian light exposure influences cardiometabolic health, yet the extent to which genetic variation modifies this relationship remains unclear. We investigated whether the MTNR1B rs10830963 genotype was associated with differences in blue-light exposure (BLE) patterns and blood lipid profiles in 63 Arctic residents (35 G-allele carriers) measured around the winter solstice and spring equinox. Participants were grouped by genotype (CC homozygotes vs. G-allele carriers) and contributed week-long actigraphy data analyzed using time-resolved analyses, mixed-effects models, and cosinor modeling. Genotype group differences across seasons were observed in light-hygiene indices, including the normalized amplitude of BLE (NA BLE) and the nocturnal excess index of BLE (NEI). G-allele carriers also exhibited a less favorable lipid profile, with higher morning low-density lipoprotein cholesterol (LDL-C), TG/HDL-C ratio, and Castelli Risk Index I, together with lower HDL-C when the two seasons were considered together. Overall, a larger NA BLE was associated with lower TG, TG/HDL-C ratio, and Castelli Risk Index I, and higher HDL-C, with these associations more evident in G-allele carriers. Time-resolved analyses further showed that associations between morning fasting lipid values and 24 h BLE, assessed across 30 min exposure bins within each season, were rhythmically patterned and more evident in G-allele carriers, with descriptively later acrophases. These findings suggest that MTNR1B rs10830963 may be associated with differences in the relationship between seasonal light exposure and lipid metabolism in Arctic residents.