Attenuation of vagal recovery during sleep and reduction of cortisol/melatonin ratio in late afternoon associate with prolonged daytime sleepiness among media workers with irregular shift work

• Published in: American journal of industrial medicine Vol. 55; no. 7; pp. 643 - 649
• Main Authors: Lindholm, Harri, Sinisalo, Juha, Ahlberg, Jari, Hirvonen, Ari, Hublin, Christer, Partinen, Markku, Savolainen, Aslak
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-07-2012; Wiley-Liss
• Subjects: Adult; Analysis of Variance; Biological and medical sciences; Cardiac dysrhythmias; Cardiology. Vascular system; Chi-Square Distribution; Circadian Rhythm; Confidence Intervals; cortisol; Female; Finland; Health Status Indicators; Heart; Heart Rate - physiology; heart rate variability; Humans; Hydrocortisone - analysis; Male; Mass Media; media work; Medical sciences; melatonin; Melatonin - analysis; Odds Ratio; recovery; Saliva; Self Report; Sleep - physiology; Statistics as Topic; Surveys and Questionnaires; Time Factors; Work Schedule Tolerance - physiology; Work Schedule Tolerance - psychology; Europe; Finland; Human; Corticosteroid; Melatonin; Arrhythmia; media work; Steroid hormone; Cardiovascular disease; Cortisol; Hydrocortisone; Glucocorticoid; Recovery; Shift work; Somnolence; Sleep; heart rate variability; Heart disease; Adrenal hormone; Working time table; Journalism; Sleep wake cycle; Mass media; Pineal hormone
• ISSN: 0271-3586; 1097-0274
• DOI: 10.1002/ajim.22042

Background
Media work is characterized by information flow, deadlines, and 24/7 alertness. Good recovery prevents stress‐related disorders.
Methods
The standardized questionnaire included items about health, health habits, sleep, work conditions, and work stress. Recordings of 24‐hr heart rate variability (HRV) and four salivary samples for cortisol and melatonin levels were analyzed from 70 randomly selected workers with irregular shift work, and 70 workers with normal daytime work.
Results
Irregular shift work increased the risk of insufficient recovery when compared to normal daytime work (OR 2.0; P < 0.05). In the group of workers with insufficient subjective recovery, HRV was attenuated (P < 0.05) during the early hours of night, and cortisol/melatonin ratio was decreased (P < 0.05) in the afternoon.
Conclusions
Physiological changes underlying subjective feelings of insufficient recovery are measurable. Attenuated HRV during sleep reflects prolonged sympathetic drive and/or impaired parasympathetic recovery. Interactions between cortisol and melatonin hormones might be involved in the development of chronic exhaustion. Am. J. Ind. Med. 55:643–649, 2012. © 2012 Wiley Periodicals, Inc.