Sleep regulation in old people : the role of bright light and melatonin

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Sleep regulation in old people : the role of bright light and melatonin

 

Author: Ho, Shuk-ching
Title: Sleep regulation in old people : the role of bright light and melatonin
Degree: Ph.D.
Year: 2001
Subject: Older people
Sleep disorders
Melatonin -- Physiological effect
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Nursing and Health Sciences
Pages: xi, 290, [37] leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1563064
URI: http://theses.lib.polyu.edu.hk/handle/200/3838
Abstract: Given that bright light and melatonin are believed to be related to the regulation of sleep patterns, the investigator wondered if sleep could be controlled by inducing changes in melatonin rhythm by using bright light. This study focused on investigating the relationships between bright light, melatonin and sleep in elderly people. A quasi-experimental study utilising convenience sampling with intra-subject comparison was employed. The study was mainly conducted in community-based homes that care for elderly people. It was divided into two parts - The main study and the further field trial. The main study was the core of the study. The further field trial was conducted to verify the main study results. Thirty-eight institutionalized women (mean age = 79.84 years old +- SD 6.17 years old) successfully completed the main study. Ten finished the further field trial. As a result. 48 women (mean age = 80.61 years old +- SD 6.20 years old) accomplished the study. They had undergone a 6-day experimental condition in which they were exposed to red dim light in the pre-and post-bright light exposure stages and white bright light (2500 lux for 3 hours) in the bright light exposure stage. Each stage lasted two days. Data on sleep patterns were collected using a sleep log and a wrist actigraph. To monitor the changes in melatonin secretion patterns, the urinary 6-sulphatoxymelatonin (aMT6s) level was measured by the radioimmunoassay (RIA) technique. The main study results showed that there were no significant light-induced effects on sleep satisfaction level, sleep-wake parameters and 6-sulphatoxymelatonin levels, except the number of waking after sleep onset (WASOf) on Day 6. Nevertheless, the subjects indicated improvement in their quality of sleep after bright light exposure. There were significant changes in the associated sleep efficiency (SE). sleep-wake ratio (SWR). total sleep time (TST). sleep onset time (SOT) and the total time of waking after sleep onset (WASOt) on Day 5. In terms of sleep-wake parameters, only WASOf showed significant change after bright light exposure. SE, SWR and sleep onset latency (SOL) were mainly increased, while WASOf showed a decrease in about 40% of the subjects. The shift in SOT was mainly forward and was not associated with that of the sleep offset time (SoffT). When total bed time (TBT) was increased. TST tended to increase. Prominent alterations in the related sleep satisfaction level (SSL) were reported in SE, SWR, TST, TBT and WASOt after bright light exposure. In the Light On Period in the bright light exposure stage, more subjects had their aMT6s levels decreased as compared with the day before. No prominent trend of changes in the mean level were observed in the Light Off Period in the post-bright light exposure stage. The related SSLs were mainly unchanged. Subjects with the mean levels decreased tended to show an increase in SE, SWR, TST, SOL. WASOf and a decrease in WASOt. In the combined findings, no significant light-induced effects were identified on SSL, sleep-wake parameters and aMT6s levels except the WASOf on Day 6. Unlike the main study results, significant changes in the related sleep-wake parameters were found on both Days 5 and 6. The corresponding shifting in SoffT but not the SOT was significantly correlated with the alteration in SSL. In terms of the sleep-wake parameters, significant changes in the related SSLs were only found when SE, SWR were increased on Day 5, TST was increased on Days 5 and 6 and WASOt was decreased on Day 5 in the combined findings. For the mean aMT6s levels, the combined findings showed that the corresponding SOL altered significantly on Day 5, when the mean level increased. This study did not find strong evidence confirming light-induced changes in melatonin for sleep regulation in elderly people. The change trends provided valuable information for formulating a protocol for sleep management, defining sleep satisfaction and applying light treatment on elderly people. Discussion takes place on the utilisation of the findings in sleep management. The feasibility of conducting sleep studies in a field setting is demonstrated. This is important for a better understanding of sleep and the development of evidence based sleep management.

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