Circadian Rhythms of Cortisol and Melatonin in Young Adults with Different Chronotypes – a Pilot Study
Author
Ganesaratnam, Nirooshitha
Term
4. term
Publication year
2012
Submitted on
2012-06-01
Pages
127
Abstract
Vores krop følger cirka 24-timers rytmer (døgnrytmer), som styres af eksterne tidssignaler (zeitgeber) – især lys. Hjernen har et hovedur i den suprachiasmatiske kerne (SCN) i hypothalamus, der koordinerer kroppens øvrige biologiske ure. Når dette system forstyrres, kan det ses ved fx søvnproblemer og depression, med ændringer i søvnmønstre, hormoner som melatonin og kortisol samt kropstemperatur. Formålet med dette studie var at undersøge, om personer med forskellige kronotyper (morgen- vs. intermediærtype) har forskellige døgnprofiler af melatonin og kortisol. Tolv raske frivillige blev inddelt som morgen- eller intermediærtype ud fra Horne-Östberg-spørgeskemaet. Før laboratoriedelen bar deltagerne en aktigraf (et armbåndsur-lignende bevægelsesmåler) i fem døgn for at bekræfte søvnvaner. Under laboratorieopholdet blev der taget blodprøver hver time og spytprøver om morgenen. Koncentrationer af melatonin og kortisol blev målt med standard laboratorietests (ELISA). Resultatet viste ingen signifikante forskelle i de overordnede døgnrytmer for kortisol og melatonin mellem de to grupper. Intermediærtyperne havde dog en lavere amplitude og en senere timing (faseforsinkelse) i melatoninrytmen sammenlignet med morgentyperne. Da deltagerantallet var lille, er større studier nødvendige for at afgøre, om kronotyper reelt adskiller sig, og om én kronotype kan være mere udsat for depression end en anden.
Our bodies run on roughly 24-hour cycles called circadian rhythms, kept on time by external cues (zeitgebers), especially light. The brain’s master clock in the suprachiasmatic nucleus (SCN) of the hypothalamus coordinates clocks throughout the body. When this system is disrupted, it can contribute to sleep problems and depression, with changes in sleep patterns, hormones such as melatonin and cortisol, and body temperature. This study examined whether people with different chronotypes (morning vs. intermediate types) show different daily patterns of melatonin and cortisol. Twelve healthy volunteers were classified as morning or intermediate types using the Horne–Östberg questionnaire. Before the lab visit, participants wore an actigraph (a watch-like activity monitor) for five days to validate sleep habits. During a hospital stay, hourly blood samples and morning saliva samples were collected. Melatonin and cortisol levels were measured using standard laboratory assays (ELISA). Overall, there were no significant differences in the circadian rhythms of cortisol and melatonin between the two groups. However, intermediate types showed a lower amplitude and a later timing (phase delay) of the melatonin rhythm compared with morning types. Because the sample was small, larger studies are needed to determine whether chronotypes truly differ and whether one chronotype may be more prone to depression than another.
[This abstract was generated with the help of AI]
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