. Author manuscript; available in PMC: 2013 Oct 1.

Published in final edited form as: Brain Behav Immun. 2012 Jun 9;26(7):1047–1056. doi: 10.1016/j.bbi.2012.06.002

Table 4.

Correlations between nocturnal non-ACTH influences (λ_I), cortisol slopes, and sleep quality components among healthy controls.

PSQI components (higher = worse)	R-value	p-Value
Pearson correlations with λ_I: external, non-ACTH influences on cortisol secretion
Shorter duration	−.432	.008^**
Poorer quality	−.409	.013^*
Lower habitual efficacy	−.365	.029^*
Longer latency	−.341	.042^*
Greater disturbance	−.281	.097^†
Greater daytime dysfunction	−.227	.183
Greater use of sleep meds	−.086	.617
Nocturnal slope parameters
1am intercept	.689	<.001^**
Linear slope	.315	.007^**
Quadratic slope	−.385	.001^**
CAR discontinuity	−.055	.647

In healthy controls, but not patients (see Table 3), worse sleep quality across four of the seven PSQI components (i.e., higher scores) was associated with a lower value for λ_I, the parameter corresponding to the dynamic model intercept and representing the external, non-ACTH influences on cortisol. If all other parameters are held constant, increasing λ_I will move all of the cortisol values predicted by the dynamic model higher along the y-axis by a constant amount.

^**

p≤ .01.

p≤ .05.

^†

p≤ .10.