Sleep in Relation to Age, Sex, and Chronotype in Japanese Workers

The study involved 622 Japanese workers and found that the habitual bedtimes and waking times were significantly earlier across all chronotypes from the young to the aged group.

• Distributions and mean scores on the Morningness-Eveningness Questionnaire shifted slightly toward the Morning type as age increased.
• Sleep length was shorter for the Evening types compared to the Morning types, especially in those under 24 years old.
• Differences in habitual and preferred sleep length exceeded 1 hour for all age groups, particularly in those under 34 years old.
• The number of awakenings during the night increased with age for all chronotypes.
• Older Evening types tended to nap more frequently and for longer durations.
• Women under 44 years woke up earlier than men of the same age, with those aged 35-54 experiencing shorter sleep lengths.

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