1. In this systematic review and meta-analysis, there was moderate evidence that physical activity was associated with lower cortisol levels.
2. Additionally, physical activity was associated with improvements in qualitative measures of sleep quality.
Evidence Rating Level: 1 (Excellent)
Cortisol is the main hormone associated with stress and is strongly linked with a person’s sleep cycle. Physical activity is known to improve stress management and sleep quality. However, few studies have looked at the effects of physical activity on both cortisol levels and sleep. Therefore, the objective of this systematic review and meta-analysis was to investigate the association between physical activity and both sleep quality and cortisol regulation.
Of 4,143 identified records, 10 studies were included in the systematic review. Articles were included if they were original peer-reviewed studies investigating physical exercise programs in adults which included relevant non-exercise control groups and measures of both sleep and physiological stress. Studies were synthesized, and meta-analyses were performed for the assessment of a standardized mean differences of sleep and stress measures. Risk of bias was assessed using the Cochrane Risk of Bias tool. The systematic review was conducted following PRISMA guidelines. The primary outcome was the impact of physical activity on both cortisol levels and sleep quality. Secondary objectives included sub-group analyses between gender, age group, and different health conditions.
The study found that physical activity interventions were associated with reduced cortisol levels and improved sleep quality. Furthermore, no meaningful changes in this effect were observed in the various sub-group analyses. However, this review was limited by the study populations of the included articles, including several studies conducted on breast cancer patients and a low number of male participants, limiting the generalizability of the findings. Nonetheless, this study provided evidence of an association between exercise and both improved sleep quality and cortisol levels.
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