The process of assessing the efficacies of hypnotic drugs requires a statement of the purpose for the drug's use. The primary indication for use of a hypnotic agent is to improve the quality or quantity of sleep. A secondary purpose is to improve the quality of life throughout the 24-hour day. One useful distinction is-between the need for sleep improvement on a short-term (acute) versus a long-term (chronic) basis. Virtually anyone can suffer an acute sleep problem due to a variety of circumstances, including jet lag and acute situational stress. On the other hand, individuals can experience a persistent reduced quality of sleep for a variety of reasons, and this population will be quite heterogeneous. Separating people with chronic insomnia from those who suffer from acute insomnia is useful in evaluating the efficacy of a hypnotic agent.

The study populations used to study the efficacies of hypnotic drugs ideally should be heterogeneous. The exclusion criteria should be such that large segments of the population who will be treated in good clinical practice will not be eliminated. However, because impairment of sleep can be a clinical symptom associated with psychotic disorders, the standard of care is treatment of the psychotic disorder rather than prolonged use of hypnotic agents, and the exclusion of psychotic patients in clinical trials of an hypnotic agent is justified and appropriate.

Evaluating Efficacy

There are two approaches to the evaluation of sleep quality: subjective and objective. The subjective evaluation of sleep involves the use of questionnaires or interviews. The subjects indicate their evaluation of the endpoint, for example, onset of sleep, duration, awakenings, and quality. The objective approach involves the use of polysomnographic studies. In these electroencephalographic (EEG) studies the exact length of time to the onset of sleep can be measured precisely, as can sleep duration and number of awakenings. Obviously, the evaluation of the quality of the sleep is still determined by the subject. Having obtained precise sleep parameters from the polysomnograph, one can compare people with and without subjective sleep problems. Interestingly, the differences in objective sleep measurements between these two groups are relatively small. It can therefore be argued that many people who complain of sleep disturbances actually sleep quite well in an objective sense. This approach fails to recognize, however, that the experience of satisfaction is, by definition, subjective. The length of time required to fall asleep that is or is not satisfying to an individual is subjective. A statistically small reduction in sleep latency may be experienced by the subject as very valuable and desirable. Telling insomniacs that their sleep latency is actually within one standard deviation of the mean is not likely to improve their satisfaction.

In the clinical setting, the insomniac patient and the clinician are seeking increased subjective improvement in sleep. In the sleep laboratory, however, subjective measures may not coincide with objective measures. For example, tolerance to benefits from hypnotic agents often occurs in objective measures despite continued improvement with subjective questionnaires. Since the reasons for the discrepancy between subjective and objective sleep

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement