***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: STUDY OBJECTIVES To study the adaptation and readaptation processes to 1 week of night work ( 6:30 PM to 6:30 AM ) followed by 1 week of day work ( 6:30 AM to 6:30 PM ) . DESIGN Part of a r and omized , placebo-controlled , crossover field study . Here , data from the placebo arm are presented . SETTING Oil rig in the North Sea . Work schedule : 2 weeks on a 12-hour shift , with the first week on the night shift and the second week on the day shift . PARTICIPANTS Subjects complaining about problems with adjusting to shift work . Seventeen workers completed the study . INTERVENTIONS N/A. MEASUREMENTS Subjective and objective measures of sleepiness ( Karolinska Sleepiness Scale and simple serial reaction time test ) and sleep ( diary and actigraphy ) . RESULTS Both subjective and objective measures improved gradually during night work . The return to day work after 1 week on the night shift led to a clear increase in subjective sleepiness and worsening of sleep parameters . During the week on the day shift , sleepiness and sleep gradually improved , similar to the improvement seen during night work . The workers indicated that the day shift was worse than the night shift on some of the measures , e.g. , sleep length was significantly longer during the night-shift period . CONCLUSIONS This is one of few studies showing how shift workers in a real-life setting adjust to night work . Both subjective and objective sleepiness and subjective sleep improved across days . The effects were especially pronounced for the subjective data Previously we have shown that the 6-sulphatoxymelatonin rhythm of oil rig workers on a 2-week night shift ( 1800 - 0600 h ) adapts to the shift via a phase delay . We now report the findings of a study on two offshore drill crews working a 1 week day ( 1200 - 0000 h ) , 1 week night ( 0000 - 1200 h ) swing shift . Urine sample s were collected every 2 - 3 h throughout the subjective days , with over-sleep collection s , for the measurement of 6-sulphatoxymelatonin by radioimmunoassay .  One crew ( n = 11 ) , studied in November , showed no change in their 6-sulphatoxymelatonin rhythm during night shift . The other crew ( n = 7 ) , studied in March , showed a significant phase advance of the rhythm during night shift . The data indicate that both the type of shift and the season influence the direction and degree of adaptation Background : Melatonin shows potential oncostatic activity and is acutely suppressed by light exposure . Some evidence suggests an association between night work and breast cancer risk , possibly through the melatonin pathway . Methods : In a cohort of premenopausal nurses , we prospect ively studied the relation between rotating night shift work and breast cancer risk . Total number of months during which the nurses worked rotating night shifts  was first assessed at baseline in 1989 and periodically up date d thereafter . We used Cox proportional hazards models to calculate relative risks ( RRs ) and 95 % confidence intervals ( CIs ) . Results : Among 115,022 women without cancer at baseline , 1,352 developed invasive breast cancer  during 12 years of follow up . Women who reported more than 20 years of rotating night shift work experienced an elevated relative risk of breast cancer compared with women who did not report any rotating night shift work ( multivariate RR = 1.79 ; 95 % CI = 1.06–3.01 ) . There was no increase in risk associated with fewer years of rotating night work . Conclusion : Our results suggest a modestly elevated risk of breast cancer after longer periods of rotating night work . Additional studies are warranted to rule out small sample size or uncontrolled sources for confounding as alternative explanations Previous research indicates that night workers ' circadian rhythms do not adapt to night work and that disturbed sleep and wakefulness persist , even after weeks of working on night shift . We studied adjustment to 14  days of consecutive night work at an oil platform and the readjustment to day life at home , using the Karolinska sleep/wake diary . The platform workers adapted to night work within a few days , as indicated by the rapid reduction of night-work sleepiness , and by the gradual delay of bedtime to an hour commensurate with the behavior of day workers . Readaptation to day life was slower and more difficult , adding evidence of a complete adaptation to night work . We conclude that the lack of conflicting exposure to daylight in the morning may have facilitated the rapid adjustment to night work STUDY OBJECTIVES Although there are considerable data demonstrating the impact of shift work on sleep and alertness , little research has examined the prevalence and consequences of shift work sleep disorder in comparison to the difficulties with insomnia and excessive sleepiness experienced by day workers . The present study was design ed to determine the relative prevalence and negative consequences associated with shift work sleep disorder in a representative sample drawn from the working population of metropolitan Detroit . DESIGN R and om-digit dialing techniques were used to assess individuals regarding their current work schedules and a variety of sleep- and non-sleep-related outcomes . SETTING Detroit tricounty population . PARTICIPANTS A total of 2,570 individuals aged 18 to 65 years from a representative community-based sample including 360 people working rotating shifts , 174 people working nights , and 2036 working days . MEASUREMENTS AND RESULTS Using st and ardized techniques , individuals were assessed for the presence of insomnia and excessive sleepiness , based on DSM-IV and ICSD criteria . Those individuals with either insomnia or excessive sleepiness and who were currently working rotating or night schedules were classified as having shift work sleep disorder . Occupational , behavioral , and health-related outcomes were also measured . Individuals who met criteria for shift work sleep disorder had significantly higher rates of ulcers ( odds ratio = 4.18 , 95 % confidence interval = 2.00 - 8.72 ) , sleepiness-related accidents , absenteeism , depression , and missed family and social activities more frequently compared to those shift workers who did not meet criteria ( P < .05 ) . Importantly , in most cases , the morbidity associated with shift work sleep disorder was significantly greater than that experienced by day workers with identical symptoms . CONCLUSION These findings suggest that individuals with shift work sleep disorder are at risk for significant behavioral and health-related morbidity associated with their sleep-wake symptomatology . Further , it suggests that the prevalence of shift work sleep disorder is approximately 10 % of the night and rotating shift work population OBJECTIVES This study evaluated the effects of bright light and melatonin on adaptation to night work on an oil rig in the North Sea . METHODS Seventeen persons working a schedule of 2 weeks on a 12-hour shift , with the first week on night shift and the second week on day shift ( ie , the swing shift schedule ) participated . In a r and omized controlled crossover design , the shift workers received a placebo , melatonin ( 3 mg , 1 hour before bedtime ) , or bright light ( 30-minute exposure , individually scheduled ) during the first 4 days on the night shift and during the first 4 days on the day shift . Subjective and objective measures of sleepiness ( Karolinska Sleepiness Scale and a simple serial reaction-time test ) and sleep ( diary and actigraphy ) were recorded . RESULTS Subjective measures indicated that melatonin modestly reduced sleepiness at work during the day shift and increased sleep by 15 - 20 minutes per day . Bright light gave values in between those of melatonin and the placebo , but with few significant results . According to the objective measures , bright light improved sleep to a minor degree during the night shift . Hardly any side-effects were reported . CONCLUSIONS Melatonin and bright light modestly improved sleep and sleepiness in this field study . In well-controlled simulated nightwork studies , both melatonin and bright light are more effective in alleviating sleepiness and sleep problems . The less effect in this field study may be due to competing or conflicting factors present in real life or to an inoptimal timing and duration of the treatments 
    Output:
    
In conclusion , the longitudinal studies were generally consistent in showing that adaptation to night work was complete within one to two weeks of work , while re-adaptation to a daytime schedule was slower .
Shift workers reported more sleep problems than day workers .