SLEEP IN RELATION TO AGE, SEX, AND CHRONOTYPE IN JAPANESE WORKERS

The Morningness-Eveningness Questionnaire and Life Habits Inventory we re administered to 622 Japanese workers matched for sex and age. We in vestigated the distributions of the scores on the Morningness-Eveningn ess Questionnaire and sleep-wake habits by age and sex. Subjects were classified into five age groups and three chronotypes. The distributio ns and mean scores on the questionnaire advanced slightly toward the M orning type from the young to the aged group. The habitual bedtimes an d waking times were significantly earlier in all the chronotypes from the young to the aged group, and the preferred bedtimes and making tim es were also clearly earlier from the young to the aged group. The len gth of sleep was shorter for the Evening than the Morning types, espec ially in the group below 24 yr. The differences in habitual and prefer red sleep length were greater than 1 hour for all age groups, especial ly the two groups under 34 yr. The number of awakenings during night s leep increased from the young to the aged group for all chronotypes. T he older Evening type tended more toward frequent napping and longer n aptime. The variabilities of bedtime and sleep length were larger for the young and Evening type than for the old group and Morning types. F urther, the mood upon waking and satisfaction with sleep length were b etter in the aged Evening type than the young Morning type. The women under 44 yr. woke up earlier than the men of the same age, and the wom en of the 35-54 yr. groups had a shorter length of sleep than others. These may be related to childcare and housework. These results indicat ed that the phase of circadian rhythms had moved forward from the youn g to the aged group, and the individual's rhythm, of those that were a ged Morning types, showed better agreement with sleep-wake rhythms tha n did others.