The use of salivary steroids to monitor circadian rhythmicity on expeditions in the arctic.

The circadian variation in salivary cortisol concentration was investigated in four men during a traverse on foot, of the Greenland ice cap and of salivary cortisol and testosterone on a summer expedition to Spitzbergen. In both instances circadian rhythmicity was demonstrated both before leaving the U.K. and throughout the expedition. The acrophase of the rhythms followed the changes in activity patterns on both expeditions although there was a dissociation between the cortisol and testosterone following an acute 8 hr phase shift in Spitzbergen. The mesor of cortisol in both instances tended to be higher than in the U.K. but the difference was never statistically significant. This work demonstrates the feasibility of using salivary steroid concentrations to investigate their circadian rhythmicity in circumstances where frequent blood sampling would be precluded.