Associations Between Polysomnography-assessed Sleep And Urinary Hydration Markers In Black Emerging Adults

PURPOSE: This study assessed associations between polysomnography (PSG)-assessed sleep with 24-hour urinary hydration measures in a sample of Black emerging adults (ages 18-28 years). METHODS: Fifteen Black emerging adults (12 females, age = 21 ± 2.5 years; body mass index (BMI) = 25.7 ± 4.5 kg/m2; body fat = 25.8 ± 1.9%) completed 2 identical 7-day measurement bursts at baseline and 6 months later. Sleep (duration, efficiency, architecture) was captured via 2 nights of in-home PSG. Urine volume (UVOL), urine specific gravity (USG), urine color (UCOL) and urine osmolality (UOSMO) were assessed over 3 days. Spearman correlations assessed associations between baseline measures of sleep with urinary hydration measures. Change variables (6 months - baseline) were rank transformed and included in partial Pearson correlations to assess associations between changes in sleep with changes in hydration measures. Baseline sleep predictors and physical activity energy expenditure (measured with actigraphy) were included as covariates in partial Pearson correlations. RESULTS: At baseline, greater total sleep duration was associated with greater UVOL (r = 0.80; P = 0.0003), lower USG (r = -0.85; P = 0.0001), lighter UCOL (r = -0.66; P = 0.007) and lower UOSMO (r = -0.75; P = 0.001). Similarly, greater stage 2 sleep duration was associated with greater UVOL (r = 0.53; P = 0.04), lower USG (r = -0.66; P = 0.006) and lower UOSMO (r = -0.58; P = 0.02). Greater slow-wave sleep duration was also associated with lower USG (r = -0.54; P = 0.04). Lastly, improvements in sleep efficiency (r = -0.64; P = 0.03) and stage 2 sleep duration (r = -0.67; P = 0.02) from baseline to 6 months were associated with reductions in USG and UOSMO, respectively. CONCLUSIONS: Greater total sleep duration, particularly stage 2 and slow-wave sleep durations, were associated with better hydration in Black emerging adults at baseline. Furthermore, improvements in sleep efficiency and stage 2 sleep duration were associated with decreases in USG and UOSMO over 6 months, suggesting that targeting sleep hygiene may be a viable strategy to improve health behaviors, such as hydration status, in Black emerging adults. Supported by: The University of North Carolina at Greensboro’s Office of Research Engagement New & Regular Faculty Research Awards and the Health and Human Sciences Top-Off Funding Program