Circadian rhythms of body temperature in shift-workers at a coalface.

266-272. The oral temperatures of a group of coalface workers were recorded daily at intervals during their period of work underground, over a three-week cycle of day, afternoon and night shifts. The basic mean circadian rhythm of temperature observed in the group as a whole was similar in phase and in amplitude to that of a control group of young men unused to shift work. However, it appeared that the rhythm of older coalface workers differed to some extent from that of their younger colleagues, since the mean temperature in the second half of the night was significantly higher in the older men. Whether this difference is permanent, and whether it is due to age alone rather than to long experience of night-shift working, has yet to be determined. There were indications that the changes in the mean on-shift trend in temperature during the week in response to successive days of an altered sleep-waking routine were more pronounced, in the group as a whole, than the changes observed in a control group of young men when the latter were exposed to similar unusual routines. It is recommended that these findings be substantiated on a considerably larger number of coalface workers before their implications for shift working are considered.