Circadian rhythms in depression. Part I: Monitoring of the circadian body temperature rhythm.

In order to develop a sampling strategy and a method for analyzing the circadian body temperature pattern, we monitored estimates of the temperature in four ways using rectal, oral, axillary and deep body temperature from the skin surface every hour for 72 consecutive hours in 10 normal control subjects. Data obtained were analyzed with the least-squares method to estimate the circadian rhythm. Deep body temperature from the skin surface correlated better with rectal temperature than with either oral or axillary temperature in all subjects. The correlation coefficient between rectal and deep body temperature from the skin surface ranged between 0.66 and 0.89. The acrophases calculated from the deep body temperature from the skin surface every 2 h for 48 h were consistent with those based on the rectal temperature every 10 min for 72 h. We believe that monitoring of the deep body temperature from the skin surface, in this manner, at intervals of 2 h for a period of 2 days, is a promising method for investigating circadian body temperature rhythm, because it causes less discomfort than other measures and has greater statistical validity for data computation.