The Effects of Polyphasic and Ultrashort Sleep Schedules

Abstract

Despite the considerable research conducted in the last three decades on relatively regular shift-work systems, the problems associated with unusual schedules, especially during conditions of intensive work, have received very Iimited attention. But such quasi-continuous work Situations are becoming increasingly common in industrialized societies. Some of these extended work seenarios involve performance of essential services in industries such as health care, transport, and nuclear electrical power, while others involve high-responsibility tasks in extreme situations, such as rescue operations, space missions, and defense efforts. In some situations the demands of continuous performance cannot easily be met simply by sharing work through conventional shift scheduling. In such situations of extreme demand the usual adult human monophasic sleep pattern (one 6-8 hr sleep episode per 24 hr) can rarely be maintained, resulting in an accumulated sleep debt. This debt can cause a serious decrease in performance effectiveness , and compromise decision-making capabilities during critical operations. To illustrate this problem, the case of space missions will be briefly examined. Unexpected high-intensity operational demands have been the major cause for acute problems of sleep loss and severe performance degradation in the last 30 years of space exploration (see Stampi, 1991, for a review). Serious accidents have occasionally occurred as a result of such deficits in functioning. While continued improvements in space hardware and in mission planning should reduce the immediate life-threatening risks to astronauts, the growing complexity of space missions and particularly of those involving extended stays in space suggest that emergencies will never disappear. The Space Station missions will extend staytimes in orbit to 6 mo WHYWENAP