The circadian rhythms of many night-shift workers are maladapted to their imposed behavioural schedule, and this factor may be implicated in the increased occurrence of cardiovascular disease (CVD) reported in shift workers. One way in which CVD risk could be mediated is through inappropriate hormonal and metabolic responses to meals. This study investigated the responses to standard meals at different circadian times in a group of night-shift workers on a British Antarctic Survey station at Halley Bay (75 S) in Antarctica.

Twelve healthy subjects (ten men and two women) were recruited. Their postprandial hormone and metabolic responses to an identical mixed test meal of 3330 kJ were measured on three occasions:(i) during daytime on a normal working day,(ii) during night-time at the beginning of a period of night-shift work, and (iii) during the daytime on return from nightworking to daytime working. Venous blood was taken for 9 h after the meal for the measurement of glucose, insulin, triacylglycerol (TAG) and non-esterified fatty acids. Urine was collected 4-hourly (longer during sleep) on each test day for assessment of the circadian phase via 6-sulphatoxymelatonin (aMT6s) assay. During normal daytime working, aMT6s acrophase was delayed (7· 71· 0 h (...)) compared with that