Objectives: To determine whether a twice-weekly maintenance schedule of evening bright light exposure is effective in alleviating sleep maintenance insomnia on a long-term basis, after the establishment of a more favorable phase relationship between the core body temperature (CBT) rhythm and sleep.
Design: Subjects underwent light treatment while living at home. Eleven to 13 consecutive days of acute light treatment (active) were followed by a 3-month maintenance light treatment period (active or control). Subjects completed five laboratory sessions: before and after the acute phase and once a month during the maintenance period.
Setting: Sleep laboratory and subjects' homes.
Participants: Fifteen older subjects (seven women, eight men; aged 63-84) with chronic (>1 year) complaints of sleep maintenance insomnia.
Interventions: During the acute phase, all participants were exposed to evening bright light (approximately 9:00 p.m. to 11:00 p.m.;>4,000 lux). During the maintenance phase, light treatment was reduced to a twice-weekly schedule, in which the active group received bright light from approximately 9:00 p.m. to 11:00 p.m. and the control group received bright light from 3:00 p.m. to 5:00 p.m.
Measurements: During each laboratory session, polysomnographic sleep and CBT were measured.
Results: Bright light exposure during the acute treatment resulted in an average phase delay in the temperature rhythm (Tmin) of 94 minutes. Sleep quality was not improved. No significant differences between active and control subjects were found during the maintenance phase; in both groups, Tmin gradually reverted to the baseline phase position, and sleep efficiency remained unchanged.
Conclusions: Although a significant phase shift in CBT was achieved during the acute treatment phase, no improvement in sleep quality was observed. Twice-weekly light exposure was not effective in maintaining the circadian phase shift over the subsequent 3 months. Issues of compliance and alternate etiologies for the sleep maintenance insomnia are discussed.