Month-to-month variation in sleep among healthy, Scandinavian daytime workers.
Scand J Clin Lab Invest
; 74(6): 527-35, 2014 Sep.
Article
in En
| MEDLINE
| ID: mdl-24824844
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.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Sleep
/
Occupational Health
/
Healthy Volunteers
Type of study:
Prognostic_studies
/
Risk_factors_studies
Aspects:
Determinantes_sociais_saude
Limits:
Humans
Country/Region as subject:
Europa
Language:
En
Journal:
Scand J Clin Lab Invest
Year:
2014
Document type:
Article
Affiliation country:
Denmark
Country of publication:
United kingdom