Weekday DLMOs are stable in subjects who sleep one hour later on weekends

Details

• Personal Author:
  Crowley SJ ; Eastman CI ; Tseng, Chih-Yu
• Description:
  Introduction: The time of the dim light melatonin onset (DLMO), the offset (DLMOff), and the midpoint between the two are commonly used markers of circadian phase. This study examined the stability of these markers in subjects who maintained a fixed sleep schedule during the week but had later bed and wake times on weekends. We also wanted to see whether the process of collecting the melatonin profile (keeping subjects awake overnight in dim light followed by a midday nap) would itself shift circadian phase. Methods: Healthy young adults (5 males, 6 females; 26.8+/-5.7 yrs) were required to be in bed with lights out from 23:00 to 7:00 on weekdays (regardless of their previous schedule) for 23 days. On weekends they were allowed to wake up and go to bed up to one hour later and were allowed to nap between 13:30 and 16:30 (i.e. 12 hours from nocturnal sleep). Every morning the subjects were required to go outside for a minimum of 15 minutes between 8:00 and 9:00 to receive natural light. To ensure compliance, all subjects wore wrist activity monitors, light sensors around the neck, and completed Daily Sleep Logs and Daily Light Logs. There were two overnight circadian phase assessments in dim light (<5 lux) beginning on Tuesdays (days 15 and 22) in which subjects gave saliva samples every 30 minutes. Following the first phase assessment, subjects napped from approximately 13:00 to 17:00. The DLMO and DLMOff threshold was 35% of the average of the three maximum levels. Results: Analysis of the sleep log data in-between the two phase assessments showed that all subjects adhered to the weekday sleep schedule and went to bed and woke up about one hour later on weekends. Seven subjects took naps on weekends. The mean+/-SD time of the DLMO for the first and second phase assessment was 21:48+/-1.0h and 21:54+/-0.7h; the DLMOff was 6:30+/-1.1h and 6:48+/-1.0h. The absolute phase change (i.e., the phase shift giving both advances and delays a positive sign) was 0.5+/-0.2h for the DLMO, 0.7+/-0.6h for the DLMOff, and 0.4+/-0.3h for the midpoint. Conclusions: In this study, all three phase markers remained very stable in phase assessments one week apart. The phase assessment and subsequent nap, and later weekend bed times, wake times, and naps did not significantly alter phase. Hence, researchers could conduct a baseline phase assessment one week before an experimental manipulation to let subjects recover from the sleep deprivation of the phase assessment. Our results suggest that even if subjects sleep an hour later on weekends and nap 12 hours from the midpoint of their nocturnal sleep, their circadian phase will not change as long as they receive morning bright light and continue to follow a fixed weekday sleep schedule. [Description provided by NIOSH]
• Subjects:
  Circadian Rhythm Men Occupational Health Safety Sleep Sleep Initiation And Maintenance Disorders Women
• Keywords:
  Biological-function Circadian-rhythms Humans Physiological-effects Psychomotor-function Sleep-deprivation Sleep-disorders
• ISSN:
  0161-8105
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  Illinois ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  26
• NIOSHTIC Number:
  nn:20045658
• Citation:
  Sleep 2003 Jun; 26(Abstract Suppl):A96-A97
• Federal Fiscal Year:
  2003
• Performing Organization:
  Rush University Medical Center, Chicago, Illinois
• Peer Reviewed:
  False
• Start Date:
  19990930
• Source Full Name:
  Sleep
• Supplement:
  Abstract Supplement
• End Date:
  20090430
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:6552eff1bcfb54ef2524c833dc831c772d33f41063cf455c1890941ea5541bdc3ee70f0fafc9cd92c66ccc301a11b5d3b632c5383737a41643daa50dfdd0f0f4
• Download URL:
  https://stacks.cdc.gov/view/cdc/201003/cdc_201003_DS1.pdf
• File Type:
  [PDF - 35.41 KB ]