Circadian and light exposure factors of sleep efficiency: sex differences in young adults

We investigated actigraphy-based associations between sleep efficiency (SEF) and circadian rhythm metrics of motor activity (MA), light exposure (LE), and wrist temperature (WT) in young adults (YA). A cross-sectional study included 187 YA (mean age 19.03 years; 132 women) across two seasons. Actigraphy data on MA, LE, blue light exposure (BLE), and WT were collected. Multivariable regression, adjusted for sex, age, season, and BMI, examined SEF associations with circadian metrics. Higher SEF was strongly predicted by greater MA relative amplitude (MA RA; β = 0.458, p < 0.001), longer total sleep time (TST; β = 0.402, p < 0.001), and earlier MA L5 timing (β = –0.286, p < 0.001). Sex-specific effects were observed in females, who showed significant associations between higher SEF and earlier MA L5 onset (β = –0.280, p = 0.002), earlier BLE L5 onset (β = –0.303,p < 0.001), earlier WT acrophase (β = –0.189, p = 0.031), greater BLE normalized amplitude (BLE NA; β = 0.292, p = 0.002), greater WT amplitude (β = 0.202, p = 0.031), and lower WT MESOR (β = –0.312, p = 0.001), whereas similar associations were not significant in males.