Daily rumination about stress, sleep, and diurnal cortisol activity

ABSTRACT

Rumination is an involuntary cognitive process theorized to prolong arousal and inhibit proper emotion regulation. Most available research has examined individual differences in cognitive dispositions to ruminate about stress as a risk marker for psychopathology and other health problems. This intensive longitudinal study extended previous research by examining day-to-day associations of rumination about stress with objectively-measured actigraph-based sleep and diurnal salivary cortisol activity. Sixty-one healthy participants (M_age = 20.91) completed up to five ecological momentary assessments (EMA) each day and wore actigraph wristwatches for eight days (N = 488). On three of these days, participants provided five saliva samples assayed for cortisol (N = 910). On average, greater daily stress levels were associated with shorter sleep duration and higher waking cortisol levels. In day-to-day analyses, greater daily stress levels, when combined with ruminating about daily stress more than usual, was associated with higher waking cortisol levels the following morning. Ruminating more than usual about daily stress, in the context of low-stress days, was also associated with flatter diurnal cortisol slopes the next day. These findings highlight the potential influences of daily stress, and rumination about stress, on sleep and diurnal cortisol activity – two important markers of health and well-being.

KEYWORDS:

• Rumination
• sleep
• diurnal cortisol
• actigraphy
• daily diaries

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Michael R. Sladek http://orcid.org/0000-0003-1697-438X

Reagan S. Breitenstein http://orcid.org/0000-0001-9998-166X

Notes

1 The current study scored sleep using the Phillips Actiware 6 program and the validated Sadeh algorithm to measure sleep (Oakley, 1997; Sadeh, Hauri, Kripke, & Lavie, 1995; Sadeh, Sharkey, & Carskadon, 1994): A = E - 2(1/25) + E - 1(1/5) + E + E + 1(1/5) + E + 2(1/25), where A denotes activity counts and E denotes epoch. Within the Sadeh algorithm, activity counts (A) within each epoch (E) were calculated based on activity levels during the adjacent 2 min period. The threshold in the algorithm and model was set to 40, with a range of 20–80. We calculated sleep parameters based on 1-minute epochs and significant movement after at least 10 min of inactivity.

2 Because cortisol values were log transformed, the effect sizes can be interpreted as a percent change per 1-unit change in the predictor after using the formula: % change = [(e^b) − 1].

Additional information

Funding

M.R.S. is now affiliated with Harvard Graduate School of Education. This research was supported by the Arizona State University College of Liberal Arts and Sciences NS-SS-GRG Research Seed Grant. This research was also conducted with the support of the National Science Foundation Graduate Research Fellowship Program under grant number DGE-1311230 to M.R.S., the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under Award Number R01HD079520 to L.D.D, and a William T. Grant Foundation Scholar Award to L.D.D. Any opinion, findings, and conclusions expressed in this material are those of the authors and do not necessarily reflect views of funding agencies. Thanks to participants and research assistants of the ASU Transition to College Study, Andrea Gierens at Biochemisches Labor at the University of Trier for technical assistance with salivary assays, Kevin Grimm for comments on a previous version of the manuscript, and Saul Castro and HyeJung Park for assistance with data cleaning.