Psychometric properties of a Japanese version of Composite Scale of Morningness

This study aimed to assess the factor structure and validity of the Composite Scale of Morningness (CSM) in Japanese samples. A sample of 348 Japanese university students (196 men, 152 women) and 170 adults from the community (50 men, 120 women) completed a questionnaire including the CSM, the Diurnal Type Scale (DTS) and questions regarding sleeping and waking times. Four measurement models were compared, and a two-factor measurement model with Morningness/Time of day preference (alpha = 0.78) and Morning Affect/Alertness (alpha = 0.80) factors yielded the closest fit. Both Morningness/Time of day preference and Morning Affect/Alertness were positively correlated with DTS score. Morningness/Time of day preference was negatively correlated with the midpoint of sleep on weekdays and free days. The measurement model was invariant across the university and community groups. The community group, which was older, was characterized by greater morningness. The results provide evidence of the validity of the Japanese CSM, thus opening up the possibility of including Japanese samples in cross-cultural research on morningness.