Association of Urinary 6-Sulfatoxymelatonin (aMT6s) Levels and Objective and Subjective Sleep Measures in Older Men: The MrOS Sleep Study

Background: Sleep and melatonin have been associated with healthy aging. In this study, we examine the association between melatonin levels and sleep among older men.

Methods: Cross-sectional study of a community-dwelling cohort of 2,821 men aged 65 years or older recruited from six U.S. centers. First morning void urine samples were collected to measure melatonin's major urinary metabolite, 6-sulfatoxymelatonin (aMT6s). We also assessed objective and subjective sleep parameters. We used logistic regression models to calculate multivariate (MV) odds ratios (ORs), and 95% confidence intervals (CIs) adjusted for important demographic variables and comorbidities.

Results: In the overall sample, the only significant finding in fully adjusted models was that aMT6s levels were inversely associated with subjectively measured daytime sleepiness (sleepiness mean score of 5.79 in the top aMT6s quartile, and 6.26 in the bottom aMT6s quartile, MV OR, 1.32; 95% CI, 0.95-1.84; p trend ≤ .02). When restricting to men without β-blocker use (a known melatonin suppressant), aMT6s levels were significantly associated with shorter sleep time, that is, less than 5 hours (MV OR, = 1.90; 95% CI, 1.21-2.99; p trend = .01), and worse sleep efficiency, that is, less than 70% (MV OR, 1.58; 95% CI, 1.28-2.65; p trend < .001). aMT6s were not associated with subjective sleep quality or respiratory disturbance in any of our analyses.

Conclusion: Lower nocturnal melatonin levels were associated with worsened daytime sleepiness, sleep efficiency, and shorter sleep time in older men. The role of circadian interventions, and whether melatonin levels are a modifiable risk factor for poor sleep in older men, warrants further study.