Eveningness and ruminations are independently associated with poor sleep quality in healthy youths

Introduction: Evening chronotype has been associated with poor sleep quality, mood disturbances, and a greater tendency to rumination. Moreover, ruminations may mediate the association between chronotype and depression and may predict reduced sleep quality in both healthy youths and young adults with depressive symptoms. A recent study exploring the role of chronotype, depressive symptoms, and cognitive emotion regulation strategies in response to stressful events or threats (including ruminations, putting into perspective, among others) as predictors of sleep quality found that eveningness, depressive symptoms, less capability of ‘putting into perspective’ and smoking were independently associated with poorer subjective sleep quality in university students. Considering the relevance of exploring specific depressive-related ruminations, the present study aims to evaluate whether ruminations, as measured through the Ruminative Response Scale, may modify the association between chronotype and sleep quality. This study focuses on youths since the transition from adolescence to adulthood involves biological changes that increase the tendency to eveningness and the vulnerability to disturbed sleep quality and mental health disturbances. Materials and methods: A sample of 213 healthy subjects aged 22.13 ±2.3 (range 15-25, 76 males) was assessed through the reduced version of the Morningness-Eveningness Questionnaire (rMEQ), the Pittsburgh Sleep Quality Index (PSQI), and the Ruminative Response Scale (RRS). Correlations between variables of interest were estimated. Linear regression models were used to explore the effect of ruminations on the associations between chronotype and sleep quality, adjusting for age, gender, and BMI. Results: Negative correlations were found between the rMEQ and the PSQI total score (Spearman r = -0.269, p-value <0.001); positive correlations were found between the RRS and the PSQI total score (Spearman r = 0.391, p-value <0.001). No significant correlations emerged between the rMEQ and the RRS (Spearman r = -0.076, p-value = 0.267). Regression analysis with the PSQI as outcome and the rMEQ and RRS as predictors adjusted for age, gender, and BMI, showed that both rMEQ (β = -0.2, p-value <0.001) and RRS (β =0.094, p-value <0.001) were associated with the PSQI. In models including both rMEQ and RRS, significant associations were found (rMEQ β = -0.18, p-value = 0.002 and RRS β = 0.09, p-value <0.001), while in models evaluating interactions between rMEQ and RRS no significant effect was observed (β = -0.001, p-value=0.732). Conclusion: Eveningness and ruminations were associated with poor sleep quality in a sample of healthy youths. Ruminations did not significantly modify the association between chronotype and sleep quality. No interaction between chronotype and ruminations was observed. Goodness-of-fit measures suggest that depressive-related ruminations, as measured through the RRS, may explain subjective sleep quality to a greater extent than chronotype. These results suggest that repetitive thoughts with negative content may negatively impact the perceived sleep quality in the young population. Further research is required to explore if these findings may be replicated in studies using objective measurements of sleep quality and in other samples.