Endocrine Abstracts

At high latitudes over-wintering personnel are deprived of natural sunlight in winter: light of sufficient intensity and suitable spectral composition is the main factor which maintains a 24 h period in human circadian rhythms. Numerous reports of sleep problems from Polar regions prompted investigations of the underlying mechanisms. At Halley (British Antarctic Survey Base, 750S) the sun does not rise for 3 months in winter and a delay of the melatonin rhythm is observed. Thi...

Light of sufficient intensity and suitable spectral composition is the main factor which maintains a 24 h period in human circadian rhythms. At the British Antarctic Survey base of Halley (75 °S) the sun does not rise for 3 months in winter and does not set for 3 months in summer. In this isolated environment most subjects remain synchronised to the 24 h day however the melatonin rhythm and sleep are delayed in winter compared to summer. Summer timing can be restored with...