Scheduled bright light for treatment of insomnia in older adults

Abstract

Objectives: To determine whether bright light can improve sleep in older individuals with insomnia.

Design: Single-blind, placebo-controlled, 12-week, parallel-group randomized design comparing four treatment groups representing a factorial combination of two lighting conditions and two times of light administration.

Setting: At-home light treatment; eight office therapy sessions.

Participants: Thirty-six women and fifteen men (aged 63.6+/-7.1) meeting primary insomnia criteria recruited from the community.

Intervention: A 12-week program of sleep hygiene and exposure to bright ( approximately 4,000 lux) or dim light ( approximately 65 lux) scheduled daily in the morning or evening for 45 minutes.

Measurements: Within-group changes were observed for subjective (sleep logs, questionnaires) and objective (actigraphy, polysomnography) sleep measures after morning or evening bright light.

Results: Within-group changes for subjective sleep measures after morning or evening bright light were not significantly different from those observed after exposure to scheduled dim light. Objective sleep changes (actigraphy, polysomnography) after treatment were not significantly different between the bright and dim light groups. Scheduled light exposure was able to shift the circadian phase predictably but was unrelated to changes in objective or subjective sleep measures. A polymorphism in CLOCK predicted morningness but did not moderate the effects of light on sleep. The phase angle between the circadian system (melatonin midpoint) and sleep (darkness) predicted the magnitude of phase delays, but not phase advances, engendered by bright light.

Conclusion: Except for one subjective measure, scheduled morning or evening bright light effects were not different from those of scheduled dim light. Thus, support was not found for bright light treatment of older individuals with primary insomnia.

Figure 1. A Diagrammatic Representation of the Relationship between Circadian Light Sensitivity and Sleep

The effect of light exposure at different times of day (phase response curve, PRC, based on Khalsa et al., 2003) in “normal” individuals (top panel) and those with an altered relationship between their sleep and underlying circadian timing system (bottom panel) are diagrammatically represented. Note, this does not depict a phase advance, such as occurs in advanced sleep phase syndrome, rather it shows a change in the phase angle (ψ) between the sleep (φ_s, midpoint of the sleep episode shown as a grey box) and circadian (φ_c, timing of peak delay on PRC) systems. In both panels, bright light in the early night causes phase delays while light in the morning causes phase advances. The magnitude of the response of the circadian clock to light scheduled to start one hour before usual bedtime (lower horizontal arrows in both panels) is larger in the bottom panel than in the top panel while the magnitude of the response to morning light scheduled to start within 15 minutes of usual time of rising in the morning (upper arrows in both panels) is similar to that of the top panel.