| Abstract No.: | B-E2165 |
| Country: | Canada |
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| Title: | VALIDATION OF BRAIN TEMPERATURE AS A CIRCADIAN PHASE MARKER |
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| Authors/Affiliations: | 1 Philippe Boudreau*; 1 Ari Shechter; 3 André Dittmar; 3 Claudine Gehin; 3 Georges Delhomme; 3 Ronald Nocua; 2 Guy Dumont; 1 Diane B. Boivin;
1 Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, McGill University, Montreal, QC, Canada; 2 Department of Electrical and Computer Engineering, University of British Colombia, Vancouver, BC, Canada; 3 Laboratory of Materials Physics, INSA-Lyon, France
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| Content: | Objectives: Human circadian phase and amplitude are commonly assessed in controlled laboratory settings with measurement of the rectal core body temperature (CBT) cycle. However, in ambulatory conditions, invasive measurements are unsuitable. In this study, we compared the assessment of circadian phase and amplitude drawn from a rectal temperature sensor and from a newly designed, non-invasive, cerebral temperature (BT) sensor using an ultra-rapid sleep-wake cycle procedure (URSW).
Methods: Three healthy women (mean age ± SD: 27.0 ± 2.5 years), with regular menstrual cycles were studied individually for 5 days in time isolation for a total of five visits (two subjects entered the laboratory twice, during each phase of their menstrual cycle). After an 8-hour baseline sleep episode, participants underwent a 72-hour URSW consisting of 60-min waking episodes in dim light (<10 lux) alternating with 60-min nap episodes in total darkness. Participants remained in a semi-recumbent position during the procedure and were served balanced iso-caloric snacks during waking episodes. BT and CBT were monitored continuously throughout this procedure. To investigate time effects, an ANOVA was used with 15-min binned BT and CBT data. A dual harmonic regression model and a cross-correlation analysis were used on 1-min binned data to assess circadian phase and amplitude of BT and CBT.
Results: Data was analyzed by a two-way mixed design ANOVA (factors: type of measure x time of day). Whereas the type x time interaction was not significant (F(1,8)=3.96, p>0.05), an expected significant effect of time was observed (F(95,760)=11.60, p<0.0001). A paired t-test on the dual harmonic regression data revealed no significant difference between the phase and amplitude assessed from BT and CBT (p=0.85 and p=0.86, respectively). Similarly, cross-correlation analysis showed no phase lag between CBT and BT (mean time difference ± SD: -6 min ± 33 min, 95% CI including the zero axis).
Conclusion: Results from the dual harmonic regression and cross-correlation analysis suggest that measurements of temperature obtained via rectal and cerebral temperature sensors have similar circadian phase and amplitude. It also suggests that BT is an acceptable non-invasive alternative to CBT for the assessment of circadian phase. |
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