3. Results
3.1. Exaggerated MBPS and sympathetic changes under cold conditions
During baseline recording, DBP in cold conditions was significantly
higher than under warm conditions (Table 1). The mean
ambient temperatures in cold and warm conditions were
16.67 ± 0.45 C and 24.40 ± 0.78 C, and the mean difference
between the two conditions was 7.73 C (P < 0.001). Higher RR,
HF and NBT together with lower LF/HF and LF% values were prominent
during the night of sleep (from 12:00 to 07:30) than during
waking (from 07:30 to 09:00); in parallel, lower RR, HF and NBT
values together with higher LF/HF and LF% values were found during
waking compared to sleep. When the participants were in the
sleep laboratory (21:30 to 09:00), the ambient temperature was
kept within a narrow range (Fig. 1, Ta, lower panel). The NBT and
Ta did not show a circadian rhythm of skin temperature throughout
the study period, confirming that NBT and Ta measurements
were not contaminated by skin temperature.