Month-to-month variation in sleep among healthy, Scandinavian daytime workers. (September 2014)

• Record Type: Journal Article
• Authors: Garde, Anne H.; Hansen, Åse M.; Persson, Roger; Österberg, Kai; Ørbæk, Palle; Karlson, Björn; Olsen, Annemarie; Kristiansen, Jesper
• Is Part Of: Scandinavian journal of clinical & laboratory investigation. Volume 74:Number 6(2014)
• Page Start: 527
• Page End: 535
• Publication Date: 2014-09
• Subjects: Clinical biochemistry -- Periodicals; Physiology, Pathological -- Periodicals; Physiology, Experimental -- Periodicals; Medicine -- Research -- Periodicals; Clinical medicine -- Periodicals; 616.0072
• DOI: 10.3109/00365513.2014.913303
• Languages: English
• ISSNs: 0036-5513

Abstract

<abstract> <title>Abstract</title> <p> <bold> <italic>Background.</italic> </bold> The overall purpose of the present study was to attain more insight in month-to-month variation of sleep duration and quality in order to improve design and interpretation of, e.g. epidemiological studies using sleep as outcome. <bold><italic>Methods.</italic></bold> The study design entailed monthly self-reports from 38 (26 women/12 men) daytime workers, who completed the Karolinska Sleep Diary (KSD) once a month during one year. A subgroup (<italic>n</italic> = 16) also wore actigraphs on one day every month during a year. Self-reports of bedtime, time of awakening, sleep duration, individual sleep characteristics, disturbed sleep index (DSI, 4 items) and awakening index (AWI, 3 items) were analyzed together with actigraphy-derived measures. Hours of daylight were used to test for circa-annual variation in statistical models adjusted for intake of hypnotics and alcohol, gender, age and within-person variability. <bold><italic>Results.</italic></bold> Hours of daylight were found to be associated to self-reported bedtime (<italic>p</italic> = 0.032) and DSI (<italic>p</italic> = 0.030), thereby indicating a circa-annual variation. Bedtime was delayed by 1.8 min (95% CI: 0.6–2.9 min) per 1 hour increase in length of daylight. Sleep was slightly more disturbed during the winter. <bold><italic>Conclusion.</italic></bold> Only circa-annual variation in self-reports of bedtime and DSI were observed in a healthy daytime working population, and the effects were small. Therefore potential bias due to circa-annuality in the studied parameters appears to be of limited concern in adult daytime working populations.</p> </abstract>