CORE BODY-TEMPERATURE AND CIRCADIAN-RHYTHM OF HOT FLASHES IN MENOPAUSAL WOMEN

Postmenopausal hot flashes are characterized by sweating and periphera l vasodilation and occur more frequently during increased heat loads. The circadian rhythm of core body temperature (T-C) is well known and suggests that hot flashes will be most frequent when core temperature is highest. This hypothesis has not been tested previously. Ten sympto matic and sis: asymptomatic postmenopausal. women were recruited from advertisements and screened. Each received 24-h ambulatory monitoring of sternal skin conductance levels to detect hot flashes, ambient temp erature, skin temperature, and T-C. The last measure was recorded usin g an ingested radiotelemetry pill. Cosinor analysis demonstrated a cir cadian rhythm (P < 0.02) of hot flashes with a peak at about 1825 h. T -C values of the symptomatic women were lower than those of the asympt omatic women (P < .05) from 0000 - 0400 h and at 1500 and 2200 h. The majority of hot flashes were preceded by elevations in T-C. Thus, elev ated T-C may serve as one trigger of menopausal hot flashes.