[The results of investigation by the Japanese version of Morningness-Eveningness Questionnaire].

Morningness-Eveningness Questionnaire (MEQ) developed by Horne & Ostberg (1976) was translated into Japanese, and then, MEQ and Life Habits Inventory were administered to approximately 1,500 university students. The distribution of MEQ scores was essentially normal, and the reliability of this questionnaire was high (r alpha = .702). Comparing among the morning, evening, and intermediate types, it was found that the morning type retired and arose significantly earlier than other types, although there was no significant differences in sleep length. Furthermore, there were significant differences between the morning and evening types in sleep latency, mood on arising, adequate amount of sleep, frequency and duration of nap, and number of staying awake all night per month. These results suggested that the evening type had more irregular sleep-waking habits than the morning type. Since the above results were obtained only from student population, further investigation on various populations is requested.