APSS: Circadian Rhythm Alterations Underlie Sleep Disruptions in Elderly

By Nancy Walsh, Contributing Writer, MedPage Today
Published: June 12, 2010
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner

SAN ANTONIO -- Discrepancies in choice of bedtime and wake time with respect to the underlying circadian system may contribute to sleep disruption in older adults with sleep complaints, a study reported here found.

Supporting this concept was the finding that the interval between habitual bedtime and secretion of melatonin (relative dim light melatonin onset) was significantly longer in a group of patients with sleep complaints compared with those who had no sleep complaints, with a phase relationship of 1.23 versus −0.04 (P=0.004), according to Jung H. Lee, MD, of Harvard Medical School in Boston, and colleagues.

In addition, the interval between bedtime and time of the fitted peak of melatonin rhythm was significantly shorter among those with sleep complaints, with a phase relationship of 3.88 versus 4.59 (P=0.028), the researchers reported in a poster session at the annual meeting of the Associated Professional Sleep Societies.

The timing of plasma melatonin rhythm has been shown to occur at an earlier hour in older adults compared with those who are younger, and the interval between plasma melatonin midpoint and usual wake time is shorter in those who are older.

These findings might result in age-related changes in sleep quality, such as loss of late sleep consolidation and early awakening -- changes that often are associated with sleep complaints in the elderly.

To evaluate timing of sleep and melatonin rhythm in older patients with and without sleep complaints, Lee and colleagues enrolled 38 subjects ages 56 to 79 years, 18 with sleep complaints and 20 without.

Participants with sleep complaints were younger and predominantly female.

Patients underwent two to three baseline days in a sleep laboratory, followed by a constant routine or constant posture circadian phase estimation procedure lasting for at least one full circadian cycle.

Blood and saliva were collected once or twice hourly for melatonin assay, and core body temperature was measured each minute throughout the procedure.

Circadian phases were assessed by dim light melatonin onset, relative dim light melatonin onset and offset, and time to peak of melatonin rhythm.

The phase angle (or time interval) between habitual wake time and habitual bedtime and the marker of circadian phase was calculated by subtracting the timing of the circadian phase marker from wake time or bedtime.

The mean relative dim light melatonin onset was significantly earlier among those with sleep complaints, at 21.84 minutes versus 23.08 minutes (P=0.012).

Time of minimum core body temperature and relative dim light melatonin offset did not differ significantly between patients with and without sleep complaints.

Each of the measures of melatonin phase and core body temperature significantly predicted subjects' habitual bedtime, but relative dim light melatonin offset and time to peak of melatonin rhythm were stronger predictors of both bedtime and wake time (P<0.0001).

Therefore, the phase relationship between sleep-wake timing and the timing of circadian rhythm is altered in these older individuals, so that they wake during an earlier circadian phase as well as at an earlier clock hour, the investigators explained.

Furthermore, they said, "The phase angle between the onset of the circadian melatonin rhythm and the timing of habitual sleep onset was longer in older subjects with sleep complaints compared to those without sleep complaints."

Understanding the age-related changes in relative timing of the circadian system and older individuals' habitual sleep-wake patterns may aid in the development of chronobiological treatments for these patients' sleep disruption, they observed.

The study was supported by the National Institutes of Health and Kangwon National University in Korea.
No other disclosures were provided.

Primary source: Associated Professional Sleep Societies
Source reference:
Lee J, et al "Altered timing of the melatonin rhythm relative to sleep timing in older subjects with sleep complaints" APSS 2010; Poster 553.

Source: www.medpagetoday.com

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