Award Date
5-1-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Interdisciplinary Programs
First Committee Member
Graham McGinnis
Second Committee Member
Brian K. Schilling
Third Committee Member
John Mercer
Fourth Committee Member
Jinyoung Kim
Number of Pages
187
Abstract
Introduction: Chronobiology, the study of internal biological rhythms, provides essential insights into how synchronization with these rhythms influences physiological processes, including sleep, metabolism, inflammation, and cognitive function. The modern lifestyle often disrupts these natural rhythms, resulting in circadian misalignment, which has been linked to impaired health outcomes such as increased inflammation, oxidative stress, and metabolic dysregulation. While much attention has been given to chronotype, the individual preference for activity timing, and its impacts on health and performance, less is known about how chronotypical alignment influences physiological and psychological responses in specific occupational contexts or everyday life. This dissertation aims to address these gaps by comprehensively examining the role of chronobiology in modulating physiological and behavioral responses to sleep disruption, physical activity, and occupational stressors, with particular attention to wildland firefighting.Methods: Three interconnected studies were conducted to explore the impact of chronotype, social jetlag (misalignment between biological and social clocks), and exercise timing on inflammatory and oxidative stress biomarkers, sleep quality, physical activity, and mental health outcomes. In the first study, the effects of acute sleep deprivation were investigated on inflammatory and oxidative stress responses during simulated wildland firefighting scenarios in male participants. Biomarkers were assessed at baseline, immediately post-exercise, and during recovery. The second study monitored wildland firefighters over a two-week critical training period, analyzing how chronotype and social jetlag influenced inflammatory biomarkers, body composition, and recovery patterns. Chronotype and social jetlag were assessed using validated questionnaires, while physiological biomarkers were measured using blood samples collected pre- and post-training. The final study investigated the effects of aligning habitual exercise timing with chronotype in a general adult population. Physical activity levels, sleep quality, and mental health parameters were evaluated using questionnaires and statistical analyses to compare chronotypically aligned versus misaligned exercise groups. Results: The studies collectively demonstrated that circadian alignment affects physiological and psychological responses to stressors and exercise. Specifically, the acute sleep deprivation study revealed heightened inflammatory and oxidative stress responses during simulated wildland firefighting, exacerbated by sleep loss. In wildland firefighters, misalignment between chronotype and training schedules impacted inflammatory biomarkers, suggesting greater susceptibility to stress-induced physiological disruptions among those experiencing higher social jetlag. Additionally, the third study showed that chronotype-aligned exercise notably improved mental health outcomes compared to those with misaligned exercise schedules. Conclusions: This dissertation provides compelling evidence that aligning daily activities, especially physical exercise, with individual circadian preferences can optimize health, enhance performance, and improve overall quality of life. These findings highlight the critical importance of considering chronotype and circadian rhythms in occupational health and general public health interventions. Future research should further explore chronic interventions and their potential benefits in mitigating the negative effects of circadian misalignment and sleep disruption on health and performance outcomes.
Keywords
chronobiology; chronotype; circadian; social jet lag; wildland firefighter
Disciplines
Medical Physiology | Medicine and Health Sciences | Physiology
File Format
File Size
2500 KB
Degree Grantor
University of Nevada, Las Vegas
Language
English
Repository Citation
Malek, Elias, "The Role of Chronobiology in Sleep, Physical Activity, and Stress Responses: Implications for Health and Performance" (2025). UNLV Theses, Dissertations, Professional Papers, and Capstones. 5303.
https://oasis.library.unlv.edu/thesesdissertations/5303
Rights
IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/