Individual differences in the phase and amplitude of the human circadian temperature rhythm: with an emphasis on morningness–eveningness

Abstract

We studied the relationship between the phase and the amplitude of the circadian temperature rhythm using questionnaires that measure individual differences in personality variables, variables that relate to circadian rhythms, age and sex. The ambulatory core body temperature of 101 young men and 71 young women was recorded continuously over 6 days. The temperature minimum (Tmin) and amplitude (Tamp) were derived by fitting a complex cosine curve to each day’s data for each subject. Participants completed the Horne–Ostberg Morningness–Eveningness Questionnaire (MEQ), the Circadian Type Inventory (CTI) and the MMPI‐2, scored for the Psychopathology‐5 (PSY‐5) personality variables. We found that the average Tmin occurred at 03.50 h for morning‐types (M‐types), 05.02 h for the neither‐types and 06.01 h for evening‐types (E‐types). Figures were presented that could provide an estimate of Tmin given an individual’s morningness–eveningness score or weekend wake time. The Tmin occurred at approximately the middle of the 8‐h sleep period, but it occurred closer to wake in subjects with later Tmin values and increasing eveningness. In other words, E‐types slept on an earlier part of their temperature cycle than M‐types. This difference in the phase‐relationship between temperature and sleep may explain why E‐types are more alert at bedtime and sleepier after waking than M‐types. The Tmin occurred about a half‐hour later for men than women. Another interesting finding included an association between circadian rhythm temperature phase and amplitude, in that subjects with more delayed phases had larger amplitudes. The greater amplitude was due to lower nocturnal temperature.

Circadian Typology: A Comprehensive Review

“…This phase difference is around two hours both in normal day-night conditions (Baehr et al, 2000) and during a constant routine (Kerkhof & Van Dongen, 1996). This circadian phase difference is explained by endogenous factors and not by differences in sleep schedules.…”

“…ET show a higher amplitude in circadian fluctuation of body temperature in comparison to MT (Baehr et al, 2000). The strength of the human circadian system is thought to be correlated to its amplitude.…”

Chronobiological characterization of women with primary vasospastic syndrome: body heat loss capacity in relation to sleep initiation and phase of entrainment

“…It is well known that misalignment between the endogenous circadian system and the sleep-wake cycle (difference in phase of entrainment) can lead to sleep disturbances (including DIS), e.g., delayed or advanced sleep phase syndrome (8), shift work sleep disorder (19), jet lag syndrome (65), the non-24-h sleep/ wake disorder (60), and extreme M/E-type (7,21,49). A condition of marked discrepancy in sleep timing between work and free days is found particularly in E-types (designated "social jet lag").…”

What Keeps Us Awake?—the Role of Clocks and Hourglasses, Light, and Melatonin

“…We have recently collected indirect evidence that the circadian arousal signal generated by this circuitry is modulated by homeostatic sleep pressure (Schmidt et al, 2009). In this study, the interaction between these processes at the cerebral level was investi gated in chronotypes differing in circadian and homeostatic sleep-wake regula tory processes under normally entrained day-night conditions (Baehr et al, 2000;Bailey and Heitkemper, 2001;Kerkhof, 1991;Kerkhof and Van Dongen, 1996;Mongrain et al, 2004Mongrain et al, , 2006aMongrain et al, , 2006b. Extreme morning and evening chronotypes were examined at different time points within a normal waking day, while performing a sustained attention task in an fMRI environment.…”