Related Sleep Abstracts

The following abstracts are provided to help you better understand Sleep Problems and using light therapy as treatment.

Estimates of the Daily Phase and Amplitude of the Endogenous Component of the Circadian Rhythm of Core Temperature in Sedentary Humans Living Nychthemerally

Biol Rhythm Res 2000 Feb;31(1):88-107
Waterhouse J, Weinert D, Minors D, Folkard S, Owens D, Atkinson G, Nevill A, Reilly T. - Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, UK.

Summary: Fifteen healthy female subjects were studied for eight days while living conventionally. Subjects were free to choose the ways they spent their time within a framework of regular times of retiring and rising; in practice, much of the waking time was spent in sedentary activities. Nine of the subjects were aware of the natural light-dark cycle, this approximating to a 12:12 L:D schedule at the time of year when the study took place. Before the study, subjects were assessed for their degree of "morningness" by questionnaire; throughout the study, they wore a rectal probe, and an activity meter on their non-dominant wrist. The timing (phase) and amplitude of the circadian rectal temperature rhythm were assessed on each day by cosinor analysis as well as by a method based on visual inspection of the data. These two parameters were also assessed after the temperature data for each day had been "purified" by a number of methods. From these results it was possible to investigate the effect of purification upon the amplitude of the circadian rhythm of temperature. Also, the day-by-day variability of phase, and the relationship between morningness and phase, were compared using these methods of phase estimation, and using cross-correlation between data sets from adjacent days; in all cases, raw and purified temperature data were used. There was a significantly greater amount of daily variation in phase using purified rather than raw data sets, and this difference was present with all methods of purification as well as with all methods for estimating phase. Purification decreased the amplitude of the circadian temperature rhythm by about 30%. Finally, there was a significant correlation between the morningness score of the subjects and the phase of the circadian temperature rhythm, the phase becoming earlier with increasing morningness; when this relationship was re-examined using purified data, it became more marked. These results reflect the masking effects exerted upon raw temperature data by lifestyle. The extent to which the purification methods enable the endogenous component of a circadian rhythm - and, by implication, the output of the endogenous circadian oscillator - to be estimated in subjects living normally is addressed.

Association of Sleep-wake Habits in Older People with Changes in Output of Circadian Pacemaker

Lancet. 1992 Oct 17;340(8825):933-6.
Czeisler CA, Dumont M, Duffy JF, Steinberg JD, Richardson GS, Brown EN, Sanchez R, Rios CD, Ronda JM. - Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115-5817.

Summary: Many elderly people complain of disturbed sleep patterns but there is not evidence that the need to sleep decreases with age; it seems rather that the timing and consolidation of sleep change. We tried to find out whether there is a concurrent change in the output of the circadian pacemaker with age. The phase and amplitude of the pacemaker's output were assessed by continuous measurement of the core body temperature during 40 h of sustained wakefulness under constant behavioural and environmental conditions. 27 young men (18-31 years) were compared with 21 older people (65-85 years; 11 men, 10 women); all were healthy and without sleep complaints. The mean amplitude of the endogenous circadian temperature oscillation (ECA) was 40% greater in young men than in the older group. Older men had a lower mean temperature ECA than older women. The minimum of the endogenous phase of the circadian temperature oscillation (ECP) occurred 1 h 52 min earlier in the older than in the young group. Customary bedtimes and waketimes were also earlier in the older group, as was their daily alertness peak. There was a close correlation between habitual waketime and temperature ECP in young men, which may lose precision with age, especially among women. These findings provide evidence for systematic age-related changes in the output of the human circadian pacemaker. We suggest that these changes may underlie the common complaints of sleep disturbance among elderly people. These changes could reflect the observed age-related deterioration of the hypothalamic nuclei that drive mammalian circadian rhythms.

Sleep Problems in Older Adults: Putting Myths to Bed

Geriatrics. 1997 Jan;52(1):20-30.
Ancoli-Israel S. - Department of Psychiatry, University of California, San Diego, USA.

Summary: Many people believe that older adults need less sleep. However, it is not the need for sleep but the ability to sleep that diminishes with age. Older adults are objectively sleepier in the day, indicating they are not getting enough sleep at night. Their sleep is disrupted by circadian rhythm changes, disorders such as sleep disordered breathing (apnea) and periodic limb movements in sleep (PLMS), medical illness, psychiatric illness, medication use, and poor sleep habits. The physician can address each of these causes, thereby improving the night-time sleep and daytime functioning of the older adult.