The results of investigation by the Japanese version of Morningess-Eveningness questionnaire.

Approximately 1,500 university students were assessed using the Morningness-Eveningness Questionnaire, revealing high reliability (r alpha = .702).

• MEQ scores showed an essentially normal distribution among participants.
• Morning-type individuals retired and arose significantly earlier than evening and intermediate types.
• No significant differences in overall sleep length were noted among the different chronotypes.
• Significant differences were observed between morning and evening types in sleep latency, mood upon waking, perceived adequacy of sleep, frequency and duration of naps, and instances of staying awake all night.
• Evening types may exhibit more irregular sleep-waking habits compared to morning types.
• Further investigation across diverse populations is necessary to confirm these findings.

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