Jet-Lag and Shift Work: (1) Circadian Rhythms

Today it is commonplace for people to fly across several time zones on business or on holiday. Moreover, many people work at night rather than the conventional 9-to-5, not only to provide public services but also to use expensive equipment economically and engage in world-wide commerce. Both groups can experience ill-effects, known respectively as 'jet-lag' and 'shiftworker's malaise'l 4. In the short term, they feel tired and unable to concentrate, yet cannot sleep uninterruptedly during the night; they perform physical and mental tasks less well than usual and with more errors; they have no appetite and they experience indigestion or bowel upsets. As well as being troublesome at a personal level, these effects might have wider implications for example, by hampering international negotiations or reducing dexterity in a technical procedure. In the longer term also there are negative effects. For example, there is evidence for raised frequencies of menstrual disorders in airline hostessess and of gastrointestinal ulcers3 and cardiovascular morbidity in nightworkers6. A full explanation of these effects will doubtless indicate that the causes are complex and multiple, but a key issue is the 'body clock'. Here I outline its function and some of the non-pharmacological ways it can be influenced to alleviate jet-lag or shiftworker's malaise. The accompanying article by Arendt7 focuses on pharmacotherapy.