Associations Between Delayed Sleep Phase Syndrome and Daytime Napping with the Metabolic Syndrome Among Adults: Results from the Ravansar Non-Communicable Disease (RaNCD) Cohort Study.

Objective: Adverse sleep and wake patterns are associated with physical health complaints, including metabolic disorders. The aim of this study was to evaluate the relationship between delayed sleep phase syndrome (DSPS) and napping during the day with metabolic syndrome (MetS). Methods: This study was conducted on 10 065 participants aged 35-65 years using baseline data from the Ravansar Non-Communicable Disease (RaNCD) cohort study. Delayed sleep phase syndrome was evaluated through a clinical interview to rule out the possibility that the sleep complaints were a result of psychiatric disorders. Logistic and linear regression models were used to determine associations. Results: The severity of MetS was found to be higher in men, older age groups, married people, subjects with a lower education level, urban residents, smokers, people with low physical activity, and DSPS. In the fully adjusted model, the odds of having MetS were 26% (95% Confidence interval (CI): 1.08, 1.48) higher in those with DSPS compared to those without DSPS. Additionally, the odds of MetS were 18% higher in people who napped less than 1 hour per day, 26% higher in those who napped 1-2 hours per day, and 21% higher in those who napped over 2 hours per day, compared to non-nappers. All of these associations were statistically significant. The odds of having the severity of MetS were significantly 6% (95% CI: 0.01, 0.12) higher in those with DSPS compared to those without DSPS. Conclusion: The findings of this study indicate that DSPS and daytime napping are associated with an increased risk of MetS. Interventions aimed at improving sleep quality are recommended as potential strategies to help reduce the risk of developing MetS.