title: Effects of timed bright-light exposure on shift-work adaptation in middle-aged subjects.
abstract: Shift workers suffer from a constellation of symptoms that can severely compromise their ability to perform optimally on-shift. The largest single factor contributing to shift-worker problems is sleep disturbance, and there is little question that the primary cause of such sleep disturbance is circadian disruption. Recently, a number of studies have demonstrated that timed exposure to bright light can help facilitate adaptation to simulated shift-work schedules, at least in younger subjects. The aim of the current study was to assess the effects of bright-light interventions in middle-aged individuals undergoing a simulated shift-work regimen. Results indicate that although light was effective in resetting the circadian clocks of these subjects by more than 6 hours, there was little effect on measures of on-duty alertness and performance or on off-duty sleep. These findings suggest that middle-aged subjects may be less phase-tolerant than young subjects, and they raise questions concerning the utility of bright-light interventions in some shift-work populations.
mesh_terms: D000328:Adult; D000367:Age Factors; D001831:Body Temperature; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D010789:Phototherapy; D012893:Sleep Wake Disorders / Q000209:etiology / Q000628:therapy; D012895:Sleep, REM; D013997:Time Factors; D014851:Wakefulness; D014940:Work Schedule Tolerance / Q000502:physiology*