The purpose of this study was to investigate the change of nocturnal body skin temperature in children with a low waking basal body temperature. One hundred and thirty five children (9.8 yrs [SD 0.6]) were evaluated for oral temperature and daily physical activity (DPA) over four weekdays. Oral temperature was measured at the time of waking. DPA was defined as the number of daily steps, determined using accelerometry. The low temperature group (L, n=11) was defined as>1 SD below the mean waking oral temperature. We made a random selection among those children who had a higher waking oral temperature score (< 1SD below the grand mean waking oral temperature) and were put to bed at the same time as L. These served as the control group (C, n=12). Skin temperatures during sleep in L and C groups were measured using the Hardy-Dubois method. Then, the time of minimal value for the mean skin temperature during sleep was determined.
There were no significant differences in waking time or total sleeping time between L and C. However, the time of the occurrence of minimal mean skin temperature in L (4:42 [SD 1:01]) delayed significantly in comparison with C (3:53 [SD 0:30]). DPA (13,785 steps [SD 1,918]) and modified morningness-eveningness score (16.5 [SD 2.2]) in L were significantly lower as compared with C (17,960 steps [SD 3,422], 18.8 [SD2.5]).
Our results suggest that low waking oral temperature may be associated with delayed body temperature circadian rhythm. Our data also suggest that a lower level of daily physical activity may be a cause in retreatment of mean skin temperature rhythm.
