Fatigue and processing speed predict subsequent fatigue override, evidence from a coordinated analysis of six EMA studies

In daily life, people often ignore feelings of fatigue to meet cognitive demands. This ‘fatigue override’ is the ability to maintain performance despite feeling tired. In both clinical and non-clinical samples, we examined whether better performance (i.e., faster processing speed) or high fatigue levels in preceding hours predicted decreased override capacity.

We conducted coordinated analysis of six intensive longitudinal studies involving 1088 participants from clinical, non-clinical, and mixed samples in the United States. Included studies were ones where, at each measurement occasion, fatigue was measured with ecological momentary assessments and processing speed with the Symbol Search task in people’s real-world environments. For each study, coordination models were used to examine both concurrent associations between fatigue and processing speed and whether current states predicted subsequent fatigue override, and the overall effect across studies was computed with individual participant data coordinated analysis.

Experiencing greater fatigue than average was associated with slightly poorer performance on the processing speed test (overall r = -0.068, 95% CI -0.127 to -0.008, p = .027). Being more fatigued than usual and performing faster than one’s typical processing speed were each associated with stronger subsequent coupling between fatigue and speed, indicating a decreased capacity to override fatigue in the following hours (overall B = 0.047, 95% CI 0.002 to 0.091, and B = 0.044, 95% CI 0.005 to 0.083, respectively). Clinical samples demonstrated lower capacity to override fatigue.

Results suggest that both elevated fatigue and unusually high cognitive performance may signal reduced capacity to sustain performance later. This work was supported by the National Institute on Aging at the NIH [grant numbers NIH/NIA R01AG068190 and R01AG079554], the National Institute of Occupational Safety and Health [grant number 1K01OH012739], the Eunice Kennedy Shriver National Institute of Child Health and Human Development [grant number R01HD102337], and the National Institute of Arthritis and Musculoskeletal and Skin Diseases [K01AR064275]. The funders played no role in study design, data collection, analysis and interpretation of data, or the writing of this manuscript.

Center for Economic & Social Research, University of Southern California, Los Angeles, CA, USA Raymond Hernandez, Stefan Schneider & Arthur A. Stone Center for Self-Report Science, University of Southern California, Los Angeles, CA, USA Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA, USA Department of Psychology, University of Southern California, Los Angeles, CA, USA Ferkauf Graduate School of Psychology, Yeshiva University, Bronx, NY, USA Claire J. Gonzalez Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, MI, USA Department of Exercise Science, University of South Carolina, Columbia, SC, USA Department of Rehabilitation Medicine, University of Washington, Seattle, WA, USA School of Health Sciences, University of Surrey, Guildford, United Kingdom Department of Health and Exercise Science, Wake Forest University, Winston-Salem, NC, USA Department of Neurology, The Pennsylvania State University, College of Medicine, Hershey, PA, USA Department of Psychology, The Pennsylvania State University, University Park, PA, USA Department of Public Health Sciences, The Pennsylvania State University, College of Medicine, Hershey, PA, USA Center for Healthy Aging, The Pennsylvania State University, University Park, PA, USA Departments of Health Care Sciences & Neurology, Wayne State University, Detroit, MI, USA Department of Psychiatry, University of California San Diego, San Diego, CA, USA A.A.S. is a Senior Scientist with the Gallup Organization and a consultant for Lore Contagious Health.

R.C.M. is a co-founder, has equity interest, is a consultant and receives compensation from NeuroUX, a company that develops mobile cognitive tests. The terms of this arrangement have been reviewed and approved by UC San Diego in accordance with its conflict of interest policies. The other authors have no conflicts of interest to report.