Objectives We tested whether a sleep and circadian-based treatment shown to improve circadian adaptation to night shifts and attenuate negative effects on alertness, performance and sleep in young adults would also be effective in older adults.
Methods We assessed subjective alertness, sustained attention (psychomotor vigilance task, PVT), sleep duration (actigraphy) and circadian timing (salivary dim-light melatonin onset, DLMO) in 18 older adults (57.2±3.8 years; mean±SD) in a simulated shift work protocol. 4 day shifts were followed by 3 night shifts in the laboratory. Participants slept at home and were randomised to either the treatment group (scheduled evening sleep and enhanced lighting during the latter half of night shifts) or control group (ad-lib sleep and typical lighting during night shifts).
Results Compared with day shifts, alertness and sustained attention declined on the first night shift in both groups, and was worse in the latter half of the night shifts. Alertness and attention improved on nights 2 and 3 for the treatment group but remained lower for the control group. Sleep duration in the treatment group remained similar to baseline (6–7 hours) following night shifts, but was shorter (3–5 hours) following night shifts in the control group. Treatment group circadian timing advanced by 169.3±16.1 min (mean±SEM) but did not shift (−9.7±9.9 min) in the control group.
Conclusions The combined treatment of scheduled evening sleep and enhanced lighting increased sleep duration and partially aligned circadian phase with sleep and work timing, resulting in improved night shift alertness and performance.
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Contributors JFD designed the research. EDC, MPH and MJK collected the data. EDC, MPH, WW and JFD analysed the data. EDC, MPH, WW and JFD wrote the paper. All authors reviewed and approved the paper.
Funding The studies were supported by NIH grant R01 AG044416 and were carried out in the Brigham and Women's Hospital Center for Clinical Investigation, part of Harvard Catalyst (Harvard Clinical and Translational Science Center) and supported by NIH Award UL1 TR001102 and financial contributions from Brigham and Women's Hospital and from Harvard University and its affiliated academic healthcare centres. EDC was supported by NIH fellowship T32 HL007901. MJK was supported by Howard Osan Dongtan Hospital, Osan, Korea.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Partners Health Care Human Research Committee.
Provenance and peer review Not commissioned; externally peer reviewed.
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