Morningness-eveningness preference and sleep habits in Japanese office workers of different ages.

The Japanese version of the morningness-eveningness questionnaire and life habits inventory were administered to approximately 400 workers and the changes in morningness-eveningness scores and sleep-wake habits with aging were investigated. All subjects were divided into four age groups, i.e., 20's, 30's, 40's, and 50 + 60's. Morningness-eveningness scores significantly shifted to morningness preference with increased age. The results of sleep-wake habits showed that 1) there were no age-related changes for habitual sleep parameters (bedtime, arising time, and sleep length), but preferential bed and arising times significantly advanced with aging, 2) the variability of habitual sleep parameters were greater in the young than in the old, especially, on the weekend, and 3) the older the age groups were, the better the mood on arising. These findings suggested that the circadian phase was advanced and/or the period was shortened with increased age.