Cognitive performance following premature awakening from zolpidem or melatonin induced daytime sleep.

BACKGROUND: The hypnotic zolpidem and the hormone melatonin were evaluated and directly compared for their effects on performance when subjects sleeping under their influence were prematurely awakened from daytime sleep. METHOD: Non-sleep deprived volunteers (eight men and five women) received single oral doses of 5 or 10 mg melatonin (Mel-5; Mel-10), 10 or 20 mg zolpidem (Zol-10; Zol-20), or placebo immediately before retiring at 13:00. Performance testing and subjective evaluations occurred prior to dosing and following forced awakening at 15:00, 2 h after dosing. RESULTS: Compared with placebo, on being awakened under Zol-20, significant performance decrements were prevalent on 9 of 10 cognitive tasks, including grammatical reasoning, mathematical processing, and word memory. Recovery required up to 6 h post-awakening for the more complex tasks. Loss of coordination and nausea were also present on awakening under Zol-20. On being awakened under Zol-10, significant but relatively less severe and shorter duration performance decrements occurred for 4 of the 10 tasks and recovered by 4 h post-awakening. Under Mel-5 or Mel-10, performance decrements seldom occurred and were considerably less severe, briefer, and less systematic than for zolpidem. CONCLUSION: Findings indicated that when operational personnel sleeping with the aid of either 10 or 20 mg zolpidem are prematurely awakened, it would be prudent to evaluate their general well-being and possible need for assistance prior to their being permitted to depart crew-rest or to perform tasks and duties. In contrast, we found little to no evidence of deteriorated well-being or need for assistance when awakened while sleeping under the influence of melatonin.

Fatigue models for applied research in warfighting.

The U.S. Department of Defense (DOD) has long pursued applied research concerning fatigue in sustained and continuous military operations. In 1996, Hursh developed a simple homeostatic fatigue model and programmed the model into an actigraph to give a continuous indication of performance. Based on this initial work, the Army conducted a study of 1 wk of restricted sleep in 66 subjects with multiple measures of performance, termed the Sleep Dose-Response Study (SDR). This study provided numerical estimation of parameters for the Walter Reed Army Institute of Research Sleep Performance Model (SPM) and elucidated the relationships among several sleep-related performance measures. Concurrently, Hursh extended the original actigraph modeling structure and software expressions for use in other practical applications. The model became known as the Sleep, Activity, Fatigue, and Task Effectiveness (SAFTE) Model, and Hursh has applied it in the construction of a Fatigue Avoidance Scheduling Tool. This software is designed to help optimize the operational management of aviation ground and flight crews, but is not limited to that application. This paper describes the working fatigue model as it is being developed by the DOD laboratories, using the conceptual framework, vernacular, and notation of the SAFTE Model. At specific points where the SPM may differ from SAFTE, this is discussed. Extensions of the SAFTE Model to incorporate dynamic phase adjustment for both transmeridian relocation and shift work are described. The unexpected persistence of performance effects following chronic sleep restriction found in the SDR study necessitated some revisions of the SAFTE Model that are also described. The paper concludes with a discussion of several important modeling issues that remain to be addressed.