Light Levels Aboard a Submarine: Results of a Survey with a Discussion of the Implications for Circadian Rhythms.

Abstract : Circadian rhythms are daily fluctuations in physiological and behavioral functions generated by an internal pacemaker (Kelly, Smith, & Naitoh, 1989). Mismatch between the endogenous circadian rhythms and imposed activity schedules (circadian desynchrony) can be associated with decreased alertness and performance. The U.S. Congress has designated the effects of circadian rhythms on shift workers as an area needing further investigation (U.S. Congress, Office of Technology Assessment, 1991). Navy operational requirements sometimes demand the use of work schedules requiring personnel to work out of synchrony with their internal rhythms. The 6-on/l2-off schedule, which is necessitated by the intrinsic limitations in the number of personnel available aboard submarines, is an extreme example of this. On this schedule, workers not only are frequently required to work during their circadian low period, they also must live by a non-24-hr daily cycle. It is common knowledge that this is a difficult schedule to work under, and interventions to promote adaptation to this schedule could be valuable.