TY - JOUR
T1 - Month-to-month variation in sleep among healthy, Scandinavian daytime workers
AU - Garde, Anne H.
AU - Hansen, Åse Marie
AU - Persson, Roger
AU - Österberg, Kai
AU - Ørbæk, Palle
AU - Karlson, Björn
AU - Olsen, Annemarie
AU - Kristiansen, Jesper
PY - 2014/9/1
Y1 - 2014/9/1
N2 - Background. 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. Methods. 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 (n = 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. Results. Hours of daylight were found to be associated to self-reported bedtime (p = 0.032) and DSI (p = 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. Conclusion. 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.
AB - Background. 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. Methods. 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 (n = 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. Results. Hours of daylight were found to be associated to self-reported bedtime (p = 0.032) and DSI (p = 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. Conclusion. 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.
U2 - 10.3109/00365513.2014.913303
DO - 10.3109/00365513.2014.913303
M3 - Journal article
C2 - 24824844
SN - 0036-5513
VL - 74
SP - 527
EP - 535
JO - Scandinavian Journal of Clinical & Laboratory Investigation
JF - Scandinavian Journal of Clinical & Laboratory Investigation
IS - 6
ER -