Chronic jet lag produces cognitive deficits

Traveling across time zones causes disruption to the normal circadian rhyth ms and social schedules because of travelers' shift in time. As the endogen ous circadian timing system adapts slowly to new time cues, the phase relat ionship between biological rhythms and external time cues are out of synchr onization for a period of time. This disturbance of circadian rhythms has b een shown to impair physical and psychological health (Winget et al., 1984) . To test the effects of repeated jet lag on mental abilities, airline cabi n crew were compared with ground crew. Salivary cortisol was used as a phys iological marker for circadian disruption. The cabin crew group, who had a history of repeated jet lag, had significantly higher salivary cortisol lev els in an average working day. In addition, this elevated level of cortisol was only seen in the same subjects when the cabin crew were on transmeridi an flights but not domestic flights. Cabin crew also exhibited cognitive de ficits, possibly in working memory, that became apparent after several year s of chronic disruption of circadian rhythms.