Estimates of the daily phase and amplitude of the endogenous component of the circadian rhythm of core temperature in sedentary humans living nychthemerally

Jim Waterhouse, Dietmar Weinert, David Minors, Simon Folkard, Deborah Owens, Greg Atkinson, Alan Nevill, Thomas Reilly

Research output: Contribution to journalArticleResearchpeer-review

6 Citations (Scopus)

Abstract

Fifteen healthy female subjects were studied for eight days while living conventionally. Subjects were free to choose the ways they spent their time within a framework of regular times of retiring and rising; in practice, much of the waking time was spent in sedentary activities. Nine of the subjects were aware of the natural light-dark cycle, this approximating to a 12:12 L:D schedule at the time of year when the study took place. Before the study, subjects were assessed for their degree of 'morningness' by questionnaire; throughout the study, they wore a rectal probe, and an activity meter on their nondominant wrist. The timing (phase) and amplitude of the circadian rectal temperature rhythm were assessed on each day by cosinor analysis as well as by a method based on visual inspection of the data. These two parameters were also assessed after the temperature data for each day had been 'purified' by a number of methods. From these results it was possible to investigate the effect of purification upon the amplitude of the circadian rhythm of temperature. Also, the day-by-day variability of phase, and the relationship between morningness and phase, were compared using these methods of phase estimation, and using cross-correlation between data sets from adjacent days; in all cases, raw and purified temperature data were used. There was a significantly greater amount of daily variation in phase using purified rather than raw data sets, and this difference was present with all methods of purification as well as with all methods for estimating phase. Purification decreased the amplitude of the circadian temperature rhythm by about 30%. Finally, there was a significant correlation between the morningness score of the subjects and the phase of the circadian temperature rhythm, the phase becoming earlier with increasing morningness; when this relationship was re-examined using purified data, it became more marked. These results reflect the masking effects exerted upon raw temperature data by lifestyle. The extent to which the purification methods enable the endogenous component of a circadian rhythm - and, by implication, the output of the endogenous circadian oscillator - to be estimated in subjects living normally is addressed.

Original languageEnglish
Pages (from-to)88-107
Number of pages20
JournalBiological Rhythm Research
Volume31
Issue number1
DOIs
Publication statusPublished - 1 Jan 2000

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circadian rhythm
Circadian Rhythm
Temperature
purification
temperature
purification methods
Biological Clocks
Photoperiod
meters (equipment)
Wrist
methodology
lifestyle
probes (equipment)
diurnal variation
method
Life Style
Appointments and Schedules
Healthy Volunteers
solar radiation
questionnaires

Cite this

Waterhouse, Jim ; Weinert, Dietmar ; Minors, David ; Folkard, Simon ; Owens, Deborah ; Atkinson, Greg ; Nevill, Alan ; Reilly, Thomas. / Estimates of the daily phase and amplitude of the endogenous component of the circadian rhythm of core temperature in sedentary humans living nychthemerally. In: Biological Rhythm Research. 2000 ; Vol. 31, No. 1. pp. 88-107.
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abstract = "Fifteen healthy female subjects were studied for eight days while living conventionally. Subjects were free to choose the ways they spent their time within a framework of regular times of retiring and rising; in practice, much of the waking time was spent in sedentary activities. Nine of the subjects were aware of the natural light-dark cycle, this approximating to a 12:12 L:D schedule at the time of year when the study took place. Before the study, subjects were assessed for their degree of 'morningness' by questionnaire; throughout the study, they wore a rectal probe, and an activity meter on their nondominant wrist. The timing (phase) and amplitude of the circadian rectal temperature rhythm were assessed on each day by cosinor analysis as well as by a method based on visual inspection of the data. These two parameters were also assessed after the temperature data for each day had been 'purified' by a number of methods. From these results it was possible to investigate the effect of purification upon the amplitude of the circadian rhythm of temperature. Also, the day-by-day variability of phase, and the relationship between morningness and phase, were compared using these methods of phase estimation, and using cross-correlation between data sets from adjacent days; in all cases, raw and purified temperature data were used. There was a significantly greater amount of daily variation in phase using purified rather than raw data sets, and this difference was present with all methods of purification as well as with all methods for estimating phase. Purification decreased the amplitude of the circadian temperature rhythm by about 30{\%}. Finally, there was a significant correlation between the morningness score of the subjects and the phase of the circadian temperature rhythm, the phase becoming earlier with increasing morningness; when this relationship was re-examined using purified data, it became more marked. These results reflect the masking effects exerted upon raw temperature data by lifestyle. The extent to which the purification methods enable the endogenous component of a circadian rhythm - and, by implication, the output of the endogenous circadian oscillator - to be estimated in subjects living normally is addressed.",
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Estimates of the daily phase and amplitude of the endogenous component of the circadian rhythm of core temperature in sedentary humans living nychthemerally. / Waterhouse, Jim; Weinert, Dietmar; Minors, David; Folkard, Simon; Owens, Deborah; Atkinson, Greg; Nevill, Alan; Reilly, Thomas.

In: Biological Rhythm Research, Vol. 31, No. 1, 01.01.2000, p. 88-107.

Research output: Contribution to journalArticleResearchpeer-review

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