Harumi Shinkoda

Changes in sleep–wake cycle during the period from late pregnancy to puerperium identified through the wrist actigraph and sleep logs

The purpose of this study was to understand the sleep–wake cycle during the period from late pregnancy to about 3 months of postpartum by evaluating the number of actigraphic activities in four women (one multipara and three primi gravidae), and to compare the results with the findings from sleep logs. An irregularity of the sleep–wake cycle with increased number of wakings at night was notable during about 1 month after delivery, compared to the late pregnancy period, and subsequently this number tended to decrease. These results were indicative of the association between the lactation cycle to neonates and the sleep–wake cycle.

Longitudinal study for sleep–wake behaviours of mothers from pre‐partum to post‐partum using actigraph and sleep logs

Abstract To understand the sleep–wake behaviours from the fifth pre‐partum week to the 15th post‐partum week by the number of actigraphic activities and sleep logs were evaluated in 10 women. It was found that total sleep time shortened, sleep efficiency decreased, and wake after sleep onset (WASO) increased in the weeks immediately after delivery. Compared with late pregnancy, total sleep time and sleep efficiency deteriorated significantly from the delivery week to the 12th post‐partum week and there was a longer period of WASO until the 11th postpartum week. The after‐delivery sleep parameters estimated by the actigraph were worse than those estimated from sleep logs.

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

The Morningness-Eveningness Questionnaire and Life Habits Inventory were administered to 622 Japanese workers matched for sex and age. We investigated the distributions of the scores on the Morningness-Eveningness Questionnaire and sleep-wake habits by age and sex. Subjects were classified into five age groups and three chronotypes. The distributions and mean scores on the questionnaire advanced slightly toward the Morning type from the young to the aged group. The habitual bedtimes and waking times were significantly earlier in all the chronotypes from the young to the aged group, and the preferred bedtimes and waking times were also clearly earlier from the young to the aged group. The length of sleep was shorter for the Evening than the Morning types, especially in the group below 24 yr. The differences in habitual and preferred sleep length were greater than 1 hour for all age groups, especially the two groups under 34 yr. The number of awakenings during night sleep increased from the young to the aged group for all chronotypes. The older Evening type tended mote toward frequent napping and longer naptime. The variabilities of bedtime and sleep length were larger for the young and Evening type than for the old group and Morning types. Further, the mood upon waking and satisfaction with sleep length were better 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 women of the 35–54 yr. groups had a shorter length of sleep than others. These may be related to childcare and housework. These results indicated that the phase of circadian rhythms had moved forward from the young to the aged group, and the individuals rhythm, of those that were aged Morning types, showed better agreement with sleep-wake rhythms than did others.

Longitudinal Study of Mothers’ Sleep-Wake Behaviors and Circadian Time Patterns from Late Pregnancy to Postpartum – Monitoring of Wrist Actigraphy and Sleep Logs

This longitudinal study investigated sleep-wake behavior patterns during and after pregnancy, using an actimeter worn on the non-dominant wrist and a sleep log. Records were obtained from ten mothers, from the 34th week of gestation until the 15th week postpartum. Ten non-pregnant women were used as a control group, data being collected from them for 2 weeks. The sleep-wake behavior after delivery, obtained from wrist actigraphy, was greater in the postpartum period. Total sleep time, sleep efficiency, and circadian amplitude decreased in the weeks immediately following parturition, but wake after sleep onset increased. Subsequently, all the sleep and circadian variables improved slightly, but they had not returned to the levels of the non-pregnant control group even by the 15th postpartum week. The length of daytime naps increased, in order to make up for nocturnal sleep deprivation when the number of awakenings during nighttime had increased. There were significant positive correlations between total sleep time, sleep efficiency, wake after sleep onset, and the length of daytime naps, but the numbers of awakenings at night and daytime naps did not show this correlation. The total sleep time indicated by sleep logs tended to be greater than that indicated by actigraphy, but wake after sleep onset tended to be underestimated by the sleep logs. The implications of these results are discussed.

SLEEP AND CHRONOTYPE FOR CHILDREN IN JAPAN

To investigate the change in sleep-wake habits, Morningness-Eveningness preference, and sleep status by grade, 512 students aged from 6 to 18 years, were tested using the Morningness-Eveningness Questionnaire and Sleep Questionnaire. The habitual waking time showed no difference by grade, but the students above Grade 7 reported a significantly later habitual bedtime and had a shorter length of sleep on weekdays than the students below Grade 6. The students above Grade 7 reported a significant difference between habitual and preferred waking times but did not show a difference between habitual and preferred bedtimes. Although the sleep length during weekends became shorter from Grade 1, the sleep length of students above Grade 8 showed a significant difference between the weekdays and weekends; they had more than nine hours of sleep on the weekends. The percentage of students taking a nap during a school lesson significantly increased across Grades 8 to 12. The mean score on the questionnaire decreased across grades and the decrease was significant at Grade 7. Both the habitual and preferred bedtimes and waking times were later from the Morning, Intermediate, to the Evening types across grades. The difference by chronotype in preferred waking time increased for groups from the primary, junior high, to the high school. Also, the sleep lengths both weekdays and weekends decreased from the Morning, Intermediate, to the Evening type for all grades. We suggested that the delay of sleep phase, reduction of sleep length, increased daytime napping, and transition to Evening type were remarkably represented around Grade 7.