Meral N. Culver1, Braxton A. Linder1, Delaney E. Lyons1, Soolim Jeong1, Zach J. Hutchison1, Alex M. Barnett1, Catherine L. Garrett1, Jessica McNeil2, Austin N. Robinson1. 1Auburn University, Auburn, AL. 2University of North Carolina at Greensboro, Greensboro, NC.

BACKGROUND: Vitamin D receptors are in areas of the brain that regulate the sleep-wake cycle. Low vitamin D status has been linked to poorer sleep quality and shorter sleep duration, but less is known regarding the influence of vitamin D on sleep duration variability (SDV). Thus, we sought to determine whether vitamin D status was associated with SDV, in addition to self-reported and objective measures of sleep quality, in young adults (18 - 35 years old). METHODS: Sixty-five adults (33 females, age 22.7 ± 3.3 years, BMI 25.5 ± 4.0 kg/m2) participated in this study. Objective sleep efficiency, duration, and SDV (standard deviation in each participant’s nightly sleep duration) were assessed using a wrist-worn Philips Actiwatch Spectrum PLUS accelerometer (observation period: 8.2 ± 1.9 days). Participants also completed the Pittsburgh Sleep Quality Index (PSQI). We assessed plasma concentrations of 25(OH)D, the primary circulating metabolite of vitamin D using an enzyme-linked immunosorbent assay kit. Normality was assessed using the Shapiro-Wilk test. One-way ANOVAs and nonparametric Kruskal Wallis tests were used to compare sleep measures in participants characterized as vitamin D deficient (< 20 ng/mL), insufficient (21 - 29 ng/mL), and sufficient (> 30 ng/mL). We also used linear regression models controlled for BMI, sex, and race to assess associations between vitamin D status and sleep metrics RESULTS: There was a significant effect of vitamin D status on SDV (ANOVA, p = 0.002) with post hoc differences between sufficient vs. deficient (p = 0.013) and sufficient vs. insufficient (p = 0.010) groups. The overall regression was statistically significant (R2 = 0.258, p = 0.002). Furthermore, vitamin D status significantly predicted SDV (e.g., sufficient-deficient, β = -0.433, p = 0.022, 95% CI [-0.803 - -0.064]. However, there was no effect of vitamin D status on objective sleep efficiency or sleep duration, or PSQI scores (ps > 0.05). CONCLUSION: In our cohort of young adults, individuals who had insufficient or deficient vitamin D exhibited more sleep variability. Further evidence is needed to assess these associations within the context of cardiometabolic risk factors, given the strong associations between sleep patterns and cardiometabolic disease. ACKNOWLEDGEMENTS: Funding for this project was provided by NIH grants K01HL147998 and UL1TR003096 (CCTS Pilot), and the 2020 Auburn University School of Kinesiology Seed Funding Competition.

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