Nonrestorative sleep and its association with insomnia severity, sleep debt, and social jetlag in adults: Variations in relevant factors among age groups

Objective: Nonrestorative sleep (NRS) is unrefreshing sleep that is harmful to mental and physical health. Although few studies have reported the relationship between NRS and sleep problems, none have evaluated this relationship by age group. This study aimed to determine whether NRS could be associated with insomnia severity, sleep debt, and social jetlag and whether this relationship would vary with age. Methods: The 1592 participants were allocated into age groups: 18-25 years (n = 317), 26-40 years (n = 405), 41-65 years (n = 454), and >65 years (n = 416). The study used Restorative Sleep Questionnaire to assess NRS, Athens Insomnia Scale to assess insomnia severity, Sleep Debt Index to assess sleep debt, and the absolute difference in midpoints of sleep between weekdays and days off to assess social jetlag. Results: Logistic regression analysis was performed to determine the association between NRS and sleep problems. In the 18-25-year group, insomnia severity, sleep debt of >= 2 h, and social jetlag of >= 2 h; in the 26-40-year group, insomnia severity and sleep debt of >= 2 h; in the 41-65-year group, insomnia severity and sleep debt of >= 2 h; and in the >65-year group, insomnia severity were significantly associated with NRS. Conclusion: NRS was associated with insomnia severity in all age groups, with sleep debt in the young and working-age groups and social jetlag in the young age group. Different approaches to improving the NRS are required for different age groups.