0355 Donning Sunglasses at Night: Advancing Fashion and Circadian Phase of Adolescents
Introduction
Previously, we reported that evening room light and sleep restriction due to late bedtimes can reduce the expected circadian phase advances in response to morning bright light in adolescents or can shift rhythms later (delay). Here, we examine whether reducing evening light with sunglasses can rescue this effect and help rhythms shift earlier (advance).
Methods
So far, 57 adolescents (29 females; 14.1-18.0 years) completed a 14-day protocol. On days 1-7, they kept individualized 10-h sleep/dark schedules at home. On days 8-14, they lived in the laboratory. On day 8, we measured their Dim Light Melatonin Onset (DLMO). On days 9-10, they went to bed 1.5h, 3.0h, or 4.5h later. Wake time was unchanged; thus, sleep opportunity was 8.5h, 7h, and 5.5h, respectively. In each sleep restriction group, participants remained awake in room light (104±11 photopic lux; 8.5h n=9; 7h n=12; 5.5h n=8) or wore amber-lensed sunglasses (transmitted 14% of light and 10% of short wavelength light; 8.5h n=5; 7h n=4; 5.5h n=9). A control group (n=10) kept their baseline bedtime, so was not exposed to additional evening light or sleep restriction. On days 11-13, sleep/dark was gradually shifted earlier, and adolescents received three 30-min exposures of bright light (8599±885 photopic lux) upon waking. Final DLMO was measured on day 14. Multiple linear regression examined sleep restriction dose, sunglasses, and the dose-by-sunglasses interaction effects on phase shift.
Results
The control group advanced +2.1±1.0h. Greater sleep restriction reduced phase advances (dose: β=-1.31, p<.001), but evening sunglasses attenuated this effect (dose-by-sunglasses: β=1.01, p<.05). When sleep/dark was 8.5h, sunglasses produced larger advances (+1.3±0.6h) compared to no sunglasses (+0.5±0.6h) [t(12)=-2.4, p=.04]. Compared to no sunglasses, evening sunglasses prevented delays when sleep/dark was 7.0h (-0.8±1.1h vs +0.5±0.9; t(14)=-2.2, p=.04) and 5.5h (-2.6±1.2h vs +0.0±1.1h; t(15)=4.8, p<.001). With evening sunglasses and 7.0h or 5.5h sleep/dark, advances were still smaller than control (p’s≤.01).
Conclusion
Reducing evening light with amber-lensed glasses during a phase-advancing protocol with morning bright light facilitates larger advances or prevents delays in adolescents. However, ≤7h sleep/dark reduces phase advances in response to morning bright light even when evening light is reduced.
Support (if any)
R01HL146772 (Crowley)