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Title

The Validity and Feasibility of Saliva Melatonin Assessment in the Elderly
Manuscript accepted for publication, Journal of Pineal Research

Abstract

Recent work in young and middle-aged subjects suggests that melatonin levels in saliva may represent a viable alternative to serum melatonin measurement. We hypothesized that it may be a valid measure of melatonin levels in older adults as well, but features unique to the elderly may limit its utility. To study this, subjects were admitted to an academic medical center where saliva and serum specimens were collected concurrently in dim light conditions during a fourteen-hour overnight study period and analyzed for melatonin levels with radioimmunoassays. 85 subjects over the age of 65 with a broad range of medical conditions participated in the study. Subjects with dementia, depression and anemia were excluded. We found that saliva volume was inadequate for analysis (<200ul) in 23.6% of specimens, with the majority of inadequate volume specimens occurring after midnight and inadequate specimens occurring more frequently in females than in males. The correlation coefficient for saliva melatonin and serum melatonin was r=0.659 (Spearman, p<0.001), and r=0.466 for saliva DLMO and serum DLMO. Saliva melatonin levels were 30.9% of serum melatonin levels, with a wide range of ratios noted between subjects. Overall melatonin levels influenced both the correlation and ratio of saliva melatonin to serum melatonin; higher correlations and lower ratios were noted when melatonin levels were high. Saliva specimens provide an economical and practical method for melatonin assessment, however, in older adults, issues such as hyposalivation and low melatonin levels limit the feasibility and validity, respectively, of saliva melatonin.

Authors

Nalaka S. Gooneratne
Joshua P. Metlay
Wensheng Guo
Frances M. Pack
Shiv Kapoor
Allan I. Pack