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Calculating the dim light melatonin onset: the impact of threshold and sampling rate.

Authors
Molina-TA; Burgess-HJ
Source
Chronobiol Int 2011 Oct; 28(8):714-718
NIOSHTIC No.
20040290
Abstract
The dim light melatonin onset (DLMO) is the most reliable circadian phase marker in humans, but the cost of assaying samples is relatively high. Therefore, the authors examined differences between DLMOs calculated from hourly versus half-hourly sampling and differences between DLMOs calculated with two recommended thresholds (a fixed threshold of 3 pg/mL and a variable "3k" threshold equal to the mean plus two standard deviations of the first three low daytime points). The authors calculated these DLMOs from salivary dim light melatonin profiles collected from 122 individuals (64 women) at baseline. DLMOs derived from hourly sampling occurred on average only 6-8 min earlier than the DLMOs derived from half-hourly saliva sampling, and they were highly correlated with each other (r>/=0.89, p<.001). However, in up to 19% of cases the DLMO derived from hourly sampling was >30 min from the DLMO derived from half-hourly sampling. The 3 pg/mL threshold produced significantly less variable DLMOs than the 3k threshold. However, the 3k threshold was significantly lower than the 3 pg/mL threshold (p<.001). The DLMOs calculated with the 3k method were significantly earlier (by 22-24min) than the DLMOs calculated with the 3 pg/mL threshold, regardless of sampling rate. These results suggest that in large research studies and clinical settings, the more affordable and practical option of hourly sampling is adequate for a reasonable estimate of circadian phase. Although the 3 pg/mL fixed threshold is less variable than the 3k threshold, it produces estimates of the DLMO that are further from the initial rise of melatonin.
Keywords
Humans; Men; Women; Age-groups; Circadian-rhythms; Light-source; Lighting; Lighting-systems; Sampling; Analytical-methods; Salivary-glands; Chemical-analysis; Author Keywords: Circadian; Dim light melatonin onset; Phase; Sleep; Threshold
Contact
Helen J. Burgess, PhD, Biological Rhythms Research Laboratory, Rush University Medical Center, 1645 W. Jackson Blvd., Suite 425, Chicago, IL 60612
CODEN
CHBIE4
Publication Date
20111001
Document Type
Journal Article
Email Address
Helen_J_Burgess@rush.edu
Funding Type
Grant
Fiscal Year
2012
Identifying No.
Grant-Number-R01-OH-003954
Issue of Publication
8
ISSN
0742-0528
Source Name
Chronobiology International
State
IL
Performing Organization
Rush University Medical Center, Chicago, Illinois
Page last reviewed: April 12, 2019
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