Table 4. Age-adjusted mean (standard error) of salivary dehydroepiandrosterone (DHEA) according to the Effort–Reward Imbalance (ERI) model indicators and time.

	DHEA (nmol/l) by time			Interaction (ERI indicator × time)		Main effect of ERI indicator
ERI indicator	9:00	12:00*	15:00†	F (degrees of freedom)	P	F (degrees of freedom)	P
High effort				0.625 (1.89, 196.1)	0.527	1.394 (1, 104)	0.240
Absent	0.22 (0.02)	0.28 (0.03)	0.20 (0.02)
Present	0.24 (0.02)	0.28 (0.03)	0.23 (0.02)
Low reward				1.279 (1.89, 196.3)	0.280	0.001 (1, 104)	0.970
Absent	0.21 (0.02)	0.27 (0.02)	0.22 (0.02)
Present	0.26 (0.02)	0.29 (0.03)	0.21 (0.02)
High E/R ratio				0.302 (1.89, 196.6)	0.728	0.245 (1, 104)	0.622
Absent	0.22 (0.02)	0.28 (0.03)	0.20 (0.02)
Present	0.25 (0.02)	0.29 (0.03)	0.22 (0.02)
High OC				1.253 (2, 208)	0.288	0.424 (1, 104)	0.517
Absent	0.23 (0.02)	0.29 (0.03)	0.21 (0.02)
Present	0.24 (0.02)	0.27 (0.03)	0.22 (0.02)

E/R ratio: effort-to-reward ratio; OC: overcommitment to work. F- and P-values were computed with mixed-model analyses of variance, into which age, employment status, current smoking, menstruation irregularity, ovulatory phase, musculoskeletal symptoms, dental and gum diseases, and other health problems were entered as covariates.

*: P < 0.001 for the within-subject comparisons to 9:00, regardless of the ERI model indicators (paired samples t-test with the Bonferroni correction).

^†: P < 0.001 for the within-subject comparisons to 12:00, regardless of the ERI model indicators.