The Onset of Elevated Salivary Melatonin Levels. Applicability of Different Models to Define Onset

Barbara Griefahn and Sibylle Robens

Institute for Occupational Physiology at Dortmund University, Dortmund, Germany

Corresponding author: Prof. Barbara Griefahn
    Ardeystr. 67
    D-44139 Dortmund, Fed. Rep. Germany
    Telephone: +49 231 1084 221
    Fax number: +49 231 1084 400
    E-mail: griefahn@ifado.de

CEJOEM 2005, Vol.11. No.3.: 225–234

Key words:
Salivary melatonin, melatonin onset, constant routine, morningness, comparative study

Abstract:
Numerous models developed to estimate the melatonin onset complicate and even prevent the comparison between studies. This analysis aimed at the identification of models that provide plausible and comparable onsets even for melatonin profiles which were not used for their development and that are probably generally applicable. Eighteen healthy young men (16–25 yrs) completed a constant routine (24 h bed rest, 18–20°C, ≤ 30 lux, ≈ 52 dBA, hourly isocaloric diet). Salivary melatonin levels were hourly determined. Morningness was estimated with questionnaires and the physiological circadian phase position with the nadir of rectal temperature. The onsets of the individual melatonin profiles were determined with 15 different models. Three models produced plausible onsets for each individual melatonin profile, which correlated significantly with morningness and with the nadir of rectal temperature. These were two physiological models which simulated the courses of elevated N-acetyltransferase activity and of melatonin production, respectively (Brown et al., 1997) and a model which defined the onset by the time when 20% of the melatonin maximum is reached or exceeded (Sharkey and Eastman, 2002). It has been concluded that the use of either of these three models might improve the comparability between studies.

Received: 1 August 2005
Accepted: 14 October 2005

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