Circadian changes in the temperature of human beings

Temperature in man measured or recorded by different means, is not constant but varies in a predictable and rhythmic fashion. Circadian (about 24-hour) rhythms have been demonstrated and studied in healthy men and women as well as in patients under a wide variety of experimental conditions and diseases. With the help of special computer programs (Halberg's cosinor) inferential statistical analyses can be performed. There validate and characterize a biological rhythm (i.e., core temperature) by several parameters: the period (tau) the acrophase (phi) (timing of the peak), the amplitude (A) and the rhythm-adjusted mean (M). Each one of these parameters is given with its confidence limits when the studied rhythm is detectable (p less than 0.05). The human temperature (oral, rectal and skin) circadian rhythm has been validated and quantified in healthy newborns, in healthy adults on various diets (including near-fasting conditions: 220 cal/24h, casein) and various type of activities. Food intake does not appear to influence the temperature circadian rhythm. The rhythm persists with a change of period and/or acrophase during isolation underground, without time dues or clues. Its acrophase can be shifted by manipulating synchronizing factors (i.e., shift-working, transmeridian flight). Alteration of circadian temperature rhythm may result from the timed administration of certain drugs (i.e. reserpine) and from certain chronic diseases (without overt fever). A first attempt to use both thermography and chronobiological method has been made independantly by Gautherie et al [40] and Smolensky [41] in the prediction of therapeutic value of a given modality during the course of breast cancer treatment.