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Author: Chih-Ming Cheng (2007-07-15); recommended: Yeh-Liang Hsu (2007-07-15).
Note: This article is Chapter 5 of Chih-Ming Cheng’s PhD thesis “Development of a portable system for tele-monitoring of sleep in a home environment”.

Chapter 5. Conclusion and Discussion

Sleep is a basic physiological need of all humans. About 35% of all adult American was afflicts by insomnia during the course of a year [Mellinger, et al., 1985]. According to statistics of “2001 Social Development Trends Survey”, over 10% of those 15 and older Taiwanese rated their sleep quality less than perfect. About 15% of the subjects reported to have PLMS and over 30% of the elder suffer from the same problem [Directorate-General of Budget, Accounting and Statistics of Taiwan, 2001]. Significant research activities are underway in the development of sleep monitoring systems. However, a basic problem is that, it requires specialists with a high degree of technical expertise and the use of an expensive polygraph. Nowadays, small, portable, non-invasive, non-constrictive, non-conscious and remote monitoring techniques are new approaches for sleep monitoring at home.

This research develops a tele-monitoring system for sleep (called the Sleep Guardian system) based on the Portable Telehomecare Monitoring System (PTMS) structure. This system embraces a snoring and OSAS symptoms detector (SOD), a physical activity detecting system (PAD-Mat) and a sleep diagnosis interface. The Sleep Guardian system on-line monitors the symptoms of sleep-related disorders and evaluates sleep stages and sleep quality via physical activity data. This portable tele-monitoring system provides a convenient approach to better understand and recognize sleep-related problems.

5.1 Possible applications of the Sleep Guardian system

Several applications are purposed in this research. The Sleep Guardian system can be used as prior examinations for sleep-related breathing disorders and PLMS, a tool for sleep quality evaluating and an assistant for nursing home supporting.

(1)    Sleep-related breathing disorder

In clinic practices, excessive daytime sleepiness is the major symptom of patients with obstructive sleep apnea syndrome (OSAS). Epworth Sleepiness Scale (ESS), a simple questionnaire measuring the general level of daytime sleepiness, is used to forewarn the possibility of OSAS. Patients with higher scores of ESS (over 10) were assigned to have PSG examinations. Although some researches showed the relation of sleepiness to respiratory disturbance [Gottlieb, et al., 1999], some others also have different point of view. Chervin and Aldrich used regression models and retrospective data from a relatively large series of 237 patients and concluded that the ESS may not reflect objective measures of sleep apnea [Chervin and Aldrich, 1999]. Guilleminault et al. also pointed out that respiratory disturbance index and oxygen saturation indices did not significantly correlate with daytime sleepiness [Guilleminault, eta al., 1988]. However, the ESS tends to amplify the possible of OSAS. In this research, “Development of a portable system for tele-monitoring of sleep in a home environment”, 18 patients who had high scores were selected for one-night PSG examination. Only 5 of 18 patients (27.8%) were classified as OSAS patient by PSG.

The SOD showed a good performance in detecting snore and locating OSAS segments (an average sensitivity of 94.0% and 79.6%). The SOD is not intended to be a diagnosis device for OSAS, instead, this portable device is to be used as a home appliance as a precautionary measure for monitoring snoring and OSAS.

(2)    Sleep quality assessment

In this research, the sleep quality evaluation is based on the Pittsburgh Sleep Quality Index (PSQI). The PSQI was designed to differentiate between good and poor sleepers, and to measures sleep disturbances using self-reports. Using a cut-off score of 5, high sensitivity and specificity of 89.6% and 86.5% was reported with the original publication of measure [Buysse, et al., 1988]. Nevertheless, PSQI scores did not correlate well with their PSG counterparts, with the strongest relationship between PSQI and PSG sleep latency being only r = 0.3.

The Sleep Guardian system provides a quantitative measurement of sleep disturbances and evaluates sleep quality with objective estimates by the PAD-Mat and the SOD. Sleep/Awake cycle was recognized by the PAD-Mat and was validated with good sensitivity and specificity in identifying sleep states (89.5% and 84.3%). This portable device is to be used as a home appliance for better understanding sleep problems.

(3)    Physical activity detection

There are also motor disturbances that are triggered by sleep, such as restless legs syndrome (RLS) and periodic limb movements during sleep (PLMS). The PAD-Mat is a non-constrain approach to detecting motor disturbances in sleep.

Besides motor disturbances monitoring and sleep quality assessment, the PAD-Mat can be used for detecting body position changes. Bed sore is a common problem in nursing home. Usually caregivers have to change the subject’s body position every 2 hour. Figure 5-1 shows a 3-day history of a subject in a nursing home. Caregivers and family members can access the PAD-Mat for body activity tracking.

Figure 5-1. 3-day history of a subject in a nursing home

5.2 Future work

The future work of this research will focus on the commercialization of the system. More user trials are to be conducted to evaluate the user acceptance, clinical effect, and economic analysis of the Sleep Guardian system. Besides the management interface described in Chapter 4, an IE user interface written in Java is to be developed, so that the caregiver can access SOD and PAD-Mat directly from any client PC. With the two sensors (SOD and PAD-Mat) and the PTMS information structure, there are more possible applications in home telehealth. Other possible applications are to be explored in the future.


Chervin, R. D., and Aldrich, M. S., “The Epworth Sleepiness Scale may not reflect objective measures of sleepiness or sleep apnea”, Neurology, 1999, v. 52, pp.125.

Directorate-General of Budget, Accounting and Statistics of Taiwan, 2001, Social Development Trends Survey.

Gottlieb, D. J., Whitney, C. W., Bonekat, W. H., Iber, C., James, G. D., Lebowitz, M.,  Nieto, F. J. and Rosenberg, C. E., “Relation of Sleepiness to Respiratory Disturbance Index”, American Journal of Respiratory and Critical Medicine, 1999, v. 159, n. 2, pp. 502-507.

Guilleminault, C., Partinen, M., Quera-Salva, M.A., Hayes, B., Dement W. C. and Nino-Murcia, G., “Determinants of daytime sleepiness in obstructive sleep apnea”, Chest, 1988, v. 94, pp.32-37.

Mellinger, G. D., Balter, M.B. and Uhlenhuth. E.H., “Insomnia and its treatment: Prevalence and correlates”, Archives of General Psychiatry, 1985, v. 42, n. 3, pp.225-232.