Day-to-day variations in salivary cortisol measurements

Purpose: The purpose of this study was to clarify the day-to-day variations of salivary cortisol to discuss the appropriate timing for collecting saliva in a day for stress evaluation. Materials and methods: Saliva samples from twelve healthy adults were collected by means of Salivette (R) (SARSTEDT Co.) three times per day, immediately after awakening (Time1), 6:00 PM (Time2) and 30 min before going to bed (Time3), on 5 nonconsecutive days. Cortisol concentration was measured using a radioimmunoassay. Results: Salivary cortisol concentration showed the larger value at Time1 than that at Time2. The mean value of %CV for day-to-day variation showed the smallest value at Time1 (mean: 43.1%) and the largest value at Time3 (mean: 100.3%). There were significant differences in %CV value between Time1 and Time3, Time2 (mean: 64.1%) and Time3. Conclusions: There are considerable day-to-day variations in salivary cortisol concentration measurements. From the viewpoint of day-to-day variation, collecting saliva immediately after awakening in the morning is thought to be more advantageous for evaluating cortisol concentration. (C) 2011 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved.