Morning-type and evening-type individuals differ in the phase position of their endogenous circadian oscillator

• Published in: Neuroscience letters Vol. 218; no. 3; pp. 153 - 156
• Main Authors: Kerkhof, Gerard A., Van Dongen, Hans P.A.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 08.11.1996; Elsevier
• Subjects: Adult; Arousal - physiology; Biological and medical sciences; Body temperature; Body Temperature - physiology; Chronobiology; Circadian Rhythm - physiology; Constant routine; Female; Fundamental and applied biological sciences. Psychology; Human circadian rhythms; Humans; Male; Masking; Momingness-eveningness; Motor Activity - physiology; Sleep - physiology; Subjective alertness; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Masking; Subjective alertness; Momingness-eveningness; Constant routine; Human circadian rhythms; Body temperature; Human; Evening; Morning; Biological rhythm; Sleep wake cycle; Circadian rhythm; Life habit
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/S0304-3940(96)13140-2

In dealing with inter-individual phase differences in overt circadian rhythms, it is often difficult to distinguish the impact of the endogenous circadian oscillator from that of an individual's habitual lifestyle. In an attempt to resolve this uncertainty about the role of masking influences, two groups of subjects, morning-types and evening-types, were selected and monitored during entrained, habitual sleep-wake conditions and during 24 h of controlled wakefulness in a laboratory-based constant-routine procedure. Under both conditions significant differences were observed in the circadian phases of body temperature and subjective alertness. During constant routine mean between-group differences for these two variables were 2.12 and 4.28 h, respectively. Thus, evidence is provided for the endogenous nature of momingness-eveningness.