Background: Recent research has found a non-linear relationship between sleep duration and mental health/quality of life. However, it is currently unclear which age group is more affected by sleep duration and what the optimal sleep duration is for each age group. Additionally, the underlying mechanisms of the non-linear relationship between sleep duration and quality of life are not well understood.

Methods: Therefore, this study utilized questionnaire data from 20,962 participants in the Chinese PBICR-2022 database(Cross-sectional study) and constructed models to analyze the relationship between sleep duration and quality of life.

Results: The results showed that the optimal sleep duration varied among different age groups: approximately 9 h for adolescents, 8 h for early/middle-aged adults, and 7 h for older adults. Compared to other age groups, less or more sleep duration had a greater impact on mental health and quality of life in adolescents. Furthermore, mental health was found to play a significant mediating role between sleep duration and quality of life in both the less sleep group and the more sleep group, but this mediating effect was not significant among the older adults in the less sleep group, whereas the mediating effect of mental health was not significant among the middle-aged adults in the more sleep group.

Conclusions: This suggests that different age groups have different optimal sleep duration, and age may be an important factor influencing the relationship between sleep duration and mental health/quality of life, with mental health playing a mediating role in the relationship between sleep duration and quality of life.