The effect of sleep quality on multidimensional affects of medical students: an intensive longitudinal study based on the diary method.

To date, extant literature predominantly centers on the positive and negative valence dimensions of affect, with limited attention paid to the dimension of affective arousal. The purpose of the study was to examine the impact of medical students' nighttime sleep quality on their next-day multidimensional affect, exploring daily mindfulness as a mediator and neuroticism as a moderator in this relationship. A total of 122 medical students recruited from a university in China were investigated by questionnaires for 14 consecutive days, completing measures of the General Information Questionnaire and the Neuroticism Subscale of the Chinese Big Five Personality Inventory Brief Version. During the diary tracking survey, participants reported last night's sleep quality upon waking up each morning and reported state mindfulness for the day and four types of affect (positive active, positive deactive, negative active, and negative deactive) before bed every night. Results showed that sleep quality positively predicted their next-day positive active affect (β = 0.103,  < 0.001) and positive deactive affect (β = 0.123,  < 0.001) and negatively predicted their next-day negative active affect (β = -0.061,  = 0.021) and negative deactive affect (β = -0.098,  = 0.002). Daily mindfulness fully mediated these effects. Neuroticism moderated the effect on positive active affect (γ11 = 0.024,  = 0.035), indicating that individuals with higher levels of neuroticism experienced more variability in their positive active affect, which was more susceptible to the influence of the previous night's sleep quality. Findings suggested good sleep quality is a critical prerequisite for medical students to maintain optimal daily affective health, particularly important for individuals with high neuroticism in enhancing their daily positive active affect. In addition, state mindfulness may be an important intervention target to improve the affect health of medical students with low sleep quality.