The effects of skin pressure by clothing on circadian rhythms of core temperature and salivary melatonin

The present experiment investigated the effects of skin pressure by foundat ion garments (girdle and brassiere) on the circadian rhythms of core temper ature and salivary melatonin. Ten healthy females (18-23 years) maintained regular sleep-wake cycles for a week prior to participation in the experime nt. The experiments were performed from June to August 1999 using a bioclim atic chamber controlled at 26.5 degreesC +/- 0.2 degreesC and 62% +/- 3% RH . Ambient light intensity was controlled at 500 lux from 07:30 to 17:30, 10 0 lux from 17:30 to 19.30, 20 lux from 19:30 to 23:30; there was total dark ness from 23:30 to 07:30. The experiment lasted for 58h over three nights. The participants arose at 07:30 on the first full day and retired at 23:30, adhering to a set schedule for 24h, but without wearing foundation garment s. For the final 24h of the second full day, the subjects wore foundation g arments. Rectal and leg skin temperatures were measured continuously throug hout the experiment. Saliva and urine were collected every 4h for the analy sis of melatonin and catecholamines, respectively. Skin pressure applied by the foundation garments was in the range 11-17 gf/cm(2) at the regions of the abdomen, hip, chest, and back. The main results were as follows: (1) Re ctal temperatures were significantly higher throughout the day and night wh en wearing foundation garments. (2) The nocturnal level of salivary melaton in measured at 03:30 was 115.2 +/- 40.4 pg/mL (mean +/- SEM, N = 10) withou t and 51.3 +/- 18.4 pg/mL (mean +/- SEM, N = 10) with foundation garments. (3) Mean urinary noradrenaline excretion was significantly lower throughout the day and night when wearing foundation garments (p <.05), but mean urin ary adrenaline excretion was not different. The results suggest that skin p ressure by clothing could markedly suppress the nocturnal elevation of sali vary melatonin, resulting in an increase of rectal temperature.