Effect of light treatment on sleep and circadian rhythms in demented nursing home patients

Abstract

Objectives: To determine whether fragmented sleep in nursing home patients would improve with increased exposure to bright light.

Design: Randomized controlled trial.

Setting: Two San Diego-area nursing homes.

Participants: Seventy-seven (58 women, 19 men) nursing home residents participated. Mean age +/- standard deviation was 85.7 +/- 7.3 (range 60-100) and mean Mini-Mental State Examination was 12.8 +/- 8.8 (range 0-30).

Interventions: Participants were assigned to one of four treatments: evening bright light, morning bright light, daytime sleep restriction, or evening dim red light.

Measurements: Improvement in nighttime sleep quality, daytime alertness, and circadian activity rhythm parameters.

Results: There were no improvements in nighttime sleep or daytime alertness in any of the treatment groups. Morning bright light delayed the peak of the activity rhythm (acrophase) and increased the mean activity level (mesor). In addition, subjects in the morning bright light group had improved activity rhythmicity during the 10 days of treatment.

Conclusion: Increasing exposure to morning bright light delayed the acrophase of the activity rhythm and made the circadian rhythm more robust. These changes have the potential to be clinically beneficial because it may be easier to provide nursing care to patients whose circadian activity patterns are more socially acceptable.

Figure 1

Raw data and model fit for one subject before and during morning light therapy. Raw data are plotted as small dots, the traditional cosine curve is plotted as a wide, smooth line, and the extended model is plotted as a thin, dotted line. The pretreatment activity data (left-hand panel) seem to have no rhythm. The peaks of the curve clearly do not match the peaks in the data. The activity data in the treatment phase (right-hand panel) are clearly more rhythmic. The extended cosine model is clearly a better representation of the data than the cosine model. For this subject, activity rhythmicity improved after treatment, and the activity acrophase estimate shifted to a later time after treatment.

Figure 2

Treatment effects on acrophase time. Acrophase was delayed during treatment in the morning light group (P = .022). DSR = daytime sleep restriction.

Figure 3

Circular plot of acrophase shift after treatment in the four treatment groups. Note that, in the morning light group, all arrows from baseline (open circles) to treatment days (closed circles) point clockwise (i.e., delayed or moved later in the day). In the evening light group, acrophase advanced (arrows pointing counterclockwise) for some patients and delayed (arrows pointing clockwise) for others. DSR = daytime sleep restriction.

Figure 4

Dim light melatonin onset (DLMO) and phase response curve in normal older people (a) and older people who are phase advanced (b). In normal middle-aged adults, DLMO is at approximately 9:00 p.m., 2 hours before bedtime. The delay portion of the phase response curve (PRC) would begin at about 1:00 p.m. In the older patients in this study, bedtime was 7:30 p.m., and DLMO was likely to be around 5:30 p.m. This would place the beginning of the delay portion 8 hours earlier, or at 9:30 a.m., the time of the morning light treatment.