| Calculating the Dim Light Melatonin Onset: The Impact of Threshold and Sampling Rate. | |
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MedLine Citation:
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PMID: 21823817 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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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 22-24 min) 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. (Author correspondence: Helen_J_Burgess@rush.edu ). |
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Authors:
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Thomas A Molina; Helen J Burgess |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-8-8 |
Journal Detail:
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Title: Chronobiology international Volume: - ISSN: 1525-6073 ISO Abbreviation: - Publication Date: 2011 Aug |
Date Detail:
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Created Date: 2011-8-9 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8501362 Medline TA: Chronobiol Int Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Biological Rhythms Research Laboratory, Department of Behavioral Sciences , Rush University Medical Center , Chicago , Illinois , USA. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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