2012 Volume 17 Issue 2 Pages 193-205
Studies have shown that approximately half of young Japanese women experience consistent, remarkable coldness in their extremities. The authors previously demonstrated an association of unusual coldness with lower daily energy intake and reduced thermoregulatory sympathetic nervous system (SNS) activity in young women. This led to the hypothesis that the unusual coldness observed among these young women derives from a widening difference between core and peripheral temperatures because of lowered thermogenesis. This study aims to examine this hypothesis. Twenty women aged 18-21 years participated in this study ; ten women consistently suffer severe coldness even at thermoneutral temperature (C-group), and another ten who do not experience such coldness (N-group). Body composition, resting energy expenditure (REE), thermoregulatory SNS evaluated by heart rate variability analysis, body temperature, and cold discomfort scores using visual-analogue scales were measured in a temperature-controlled room (26℃) at 8:30 a.m. after an overnight fast on two different days. As indices of core and peripheral temperatures, eardrum, finger, and toe temperatures were measured using high-sensitivity thermo-sensors for 60 min. C-group showed a significantly lower thermoregulatory SNS and tended to have lower REE per lean body mass as compared to N-group. Eardrum temperature did not differ between the groups. Only C-group showed a significantly increased difference between core and peripheral temperatures (eardrum-finger or eardrum-toe, 0-60 min). A positive correlation was observed between eardrum-toe temperatures and cold discomfort scores at the toe. Our results suggest that women who consistently experience such coldness characteristically have 1) lowered REE. 2) increased difference in core-peripheral temperatures during 60 min, 26℃-environmental exposure despite similar core temperature, and 3) increased coldness due to wider core-peripheral temperatures, thus supporting our hypothesis.