Disentangling sources of individual differences in diurnal salivary α-amylase: Reliability, stability and sensitivity to context

Dorothée Out, Douglas A. Granger, Sandra E. Sephton, Suzanne C. Segerstrom

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


In the present study, we employ a longitudinal design and a generalizability framework to examine the sources of variance in the diurnal rhythm of salivary α-amylase (sAA). The sample consisted of 122 first-year law students (55% male, mean age = 23.9 years), who collected five saliva samples on each of three consecutive days at each of five data collection waves. In total, over 6900 saliva samples were collected, which allowed us to examine the properties of diurnal variation in sAA in great detail. Systematic individual differences accounted for 15-29% of the variability in the awakening response and diurnal slope, and for 61-65% of the variation in overall daily levels (i.e., diurnal mean, area under the curve with respect to ground [AUCg]). Although less than 1% of the variation was due to differences between waves and between days, the generalizability analyses revealed that between 16% and 17% of the variance in the diurnal mean, slope and AUCg is due to person by wave interactions, indicating that individuals vary in their biological sensitivity to environmental influences. In sum, this study documents sufficient stability and variation in diurnal sAA to warrant future studies on the origins and consequences of alterations in the diurnal rhythm of sAA worthwhile, and proposes guidelines on obtaining reliable measures.

Original languageEnglish
Pages (from-to)367-375
Number of pages9
Issue number3
StatePublished - Mar 2013

Bibliographical note

Funding Information:
DO was supported by a Rubicon award ( 446-10-026 ) from the Netherlands Organization for Scientific Research .


  • Diurnal
  • Individual differences
  • Reliability
  • Salivary α-amylase
  • Sensitivity to context
  • Stability

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology
  • Endocrine and Autonomic Systems
  • Psychiatry and Mental health
  • Biological Psychiatry


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