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. Author manuscript; available in PMC: 2015 Sep 1.
Published in final edited form as: Psychosom Med. 2014 Sep;76(7):519–528. doi: 10.1097/PSY.0000000000000097

Figure 2.

Figure 2

Figure 2

(a–b). Graphical representation of the effects of duration of prior-day nap duration and prior-night nocturnal awakenings on cortisol diurnal rhythm. These effects are modeled either as the average value as well as ±1SD of the sample mean values. Graphs are estimated by the hierarchical linear models from the time of the awakening (Wake Up) through bedtime.

(a) Longer prior-day nap duration was associated with lower cortisol at awakening (b = −0.184, p = .004), greater CAR (b = 0.042, p = .050), steeper linear (b = −0.035, p = .003) and flatter quadratic slopes (b= −0.0017, p < .001). Solid line represents nap duration at −1SD; dotted line represents average nap duration; dashed line represents nap duration at +1SD.

(b) Greater duration of nocturnal awakenings was associated with a greater cortisol at awakening only (b = 0.088, p = .043) and not CAR or linear/quadratic slope. Solid line represents duration of nocturnal awakenings at −1SD; dotted line represents average duration of nocturnal awakenings; duration; dashed line represents duration of nocturnal awakenings at +1 SD.