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The effects of lunchtime bright light exposure in patients of a geriatric hospital were investigated. Ten inpatients (six women and four men; mean age +/- SD: 81.2 +/- 8.8 years) with sleep disturbances were studied for 9 weeks. Nurses performed daily ratings for sleep-wakefulness disturbances. Approximately 8000 lx bright light exposure was performed for 3 weeks in the light therapy room. Before and after exposure, ocular function was evaluated. Clinical ratings of sleep-wakefulness improved in eight patients. The score of difficulty in falling asleep and drowsiness in the morning declined during the light exposure. The score of drowsiness in the afternoon decreased during the post-light exposure. Post-exposure ocular disturbances were not found.

To investigate the effects of evening bright light on the autonomic nervous system, heart rate variability (HRV) during sleep was analyzed in dim light (DL) and bright light (BL) conditions. We recorded polysomnography in nine healthy young women aged 20–21 years. Time series of % delta power was calculated in the 0.49–2.20 Hz band. Heart rate variability was analyzed from a 10-min segment of slow wave sleep. The low- to high-frequency ratio and the low-frequency component decreased significantly in the BL conditions compared with the DL conditions. However, the power of the high-frequency component did not change in the two conditions. These results indicate that evening BL affects the autonomic nervous system during slow wave sleep.

Inpatients with sleep disturbances in a geriatric hospital received 1 h of exposure to approximately 8000 lx bright light per day for 3 weeks. Polysomnogram was recorded for four female patients. Two (aged 68 and 87 years) were non-demented patients with weak cataracts and the other two (aged 92 and 93 years) were demented patients with severe cataracts. Electroencephalogram results showed that light exposure decreased the proportion of Stage W, while increased the proportion of Stage 2, and these effects continued for at least 3 weeks after the cessation of light exposure. These results suggest that exposure to bright light is effective in improving the disturbed sleep of patients.

Sleep structure was measured in five healthy elderly men in their homes. The subjects were exposed to bright light (6000 lx) for 30 min in the morning or instructed to sit in front of a desktop lighting device without light. Relative to the control conditions, bright light exposure significantly decreased time in bed and the number of awakenings. Rapid eye movement sleep was significantly fragmented by stage 1 sleep in the control condition compared with the bright light condition. These findings indicate that a short duration of morning bright light changes sleep structure and is effective in maintaining sleep.

We examined REM sleep periodicity in typical narcoleptics and patients who had shown signs of a narcoleptic tetrad without HLA-DRB1*1501/DQB1*0602 or DR2 antigens, using spectral analysis based on the maximum entropy method. The REM sleep period of typical narcoleptics showed two peaks, one at 70–90 min and one at 110–130 min at night, and a single peak at around 70–90 min during the daytime. The nocturnal REM sleep period of typical narcoleptics may be composed of several different periods, one of which corresponds to that of their daytime REM sleep.

Subjective sleep feeling and polysomnography were measured in 10 elderly women to investigate the effects of 8000 lux morning bright light (BL) exposure. The profile of sleep feeling in the BL condition was better than in the control condition. The proportion of awakening time in the first one-third of night sleep decreased, and the amount of awakening time in the last one-third increased in BL condition. Daytime napping reduced in BL condition. These findings suggested the effectiveness of exposure to bright light on the improvement of sleep quality and daytime vigilance of healthy elderly women.

To investigate the effects of 8000 lux morning bright light in the elderly, home-based motor activity on sleep was monitored for 5 days in 10 healthy women (mean age: 59.7 years old, range: 50-69 years old). The activity level and movement index on night 4 were significantly lower in bright light conditions, compared with the controlled condition. The activity level during the day was not significantly different between the two conditions. These results indicate that 8000 lux morning bright light improves sleep quality in healthy elderly women.

Sleep EEG of eight healthy males and eight females aged 54–72 years were recorded at their homes. The electroencephalograms were visually scored and analyzed by spectral analysis using the FFT method. There were no significant differences in sleep parameters except for a higher percentage of stage 3 + 4 in females. The spectral power of the delta band EEG was classified into two frequencies: 0.5–2 Hz and 2–4 Hz. The total amount of the delta band spectral power through the night was significantly larger in females. Periodic fluctuation of delta band power was observed in females along with non-rapid eye movement–rapid eye movement cycles.

In order to investigate the gender difference of sleep and activity in middle-aged and aged individuals, home-based sleep was self-evaluated for sleep quality and activity for 5 nights in 20 healthy adults (50-76 years old; 11 women, nine men). There was no significant gender difference for subjective sleep quality. However, the activity level and movement index at night were significantly higher in men than in women, and the activity level during the day was significantly lower in men than in women. The objective sleep quality of men was significantly worse than that of women, however, subjective sleep quality does not differ.

Using an actigraph, the activity patterns in 13 demented patients with delirium were examined. We analyzed the data of the eight patients, wearing the actigraphs for more than 10 days. They were classified into four types: type A, nocturnal delirium type; type B, wandering type; type C, hypobulia type; and type D, lying down type. The day to day activity variation was most prominent in type A and seemingly the least in type B. The dominant period of activity rhythm was nearly 24 h in all cases. Additional 12-h period was observed in type C. Actigraphs might become useful in making therapeutic decisions regarding demented patients with delirium.

Seven aged subjects aged 61-78 years were exposed to 6000 lx bright light for 30 min during morning hours at their homes for 1 week. Visual analog scale was recorded before bedtime and after rising to assess subjective feelings. Ophthalmological examinations were made before and after light exposure, to exclude pre-existing ocular disorders and to detect ocular damage. Furthermore, ocular fatigue was self-evaluated immediately before and after exposure. Visual analog scale results indicated that alertness reduced significantly before bedtime. Ophthalmological abnormalities were not found after exposure. These findings suggest that short duration morning bright light exposure reduces night-time vigilance.

In order to investigate the effects of 5000 lx evening bright light on autonomic nervous function, a spectral analysis was used to assess heart rate variability in consecutive 5-min epochs just after 60 min of bright light therapy was given to 12 young women (range: 20–21 years of age). The study revealed that a low frequency band (LF) increased in bright light conditions (BL) in comparison with controlled conditions (CL). High frequency band (HF), LF : HF ratio and the coefficient of variance (CV R-R) were not significantly different between the two conditions. These results indicate that 5000 lx evening bright light may affect sympathetic nervous system activity in healthy women.

Diagnosing narcolepsy is not always simple. Some patients secondarily show narcoleptic tetrad through irregular sleep patterns or psychotic diseases. The power densities of daytime electroencephalograms in genuine narcolepsy and secondary narcolepsy were analysed and compared. Electroencephalogram power densities for a 6.5-h period after waking in genuine narcoleptic patients were lower than those of secondary narcoleptic patients in the 11.0-12.5 Hz bands. Arousal levels may be lower in genuine narcoleptic patients than in secondary narcoleptic patients. Spectral analysis may be useful in clarifying differences between the two groups.

The study was designed to investigate gender differences in the sleep-wake patterns of healthy middle-aged individuals in their home environment. Polysomnography showed that daytime napping was more common in men than in women. Men had lower sleep efficiency index and experienced more stage 1 sleep. Males had significantly less stages 3 + 4 sleep, less stage REM sleep, and more transitions to wake from REM sleep. Men could not maintain stage REM as well as women. This study indicates that the gender differences in the sleep-wake patterns have appeared in a group of middle-aged individuals.

Subjective sleep feelings and motor activity were measured in seven healthy elderly subjects for 6 days. The subjects were exposed to bright light (6000 lux) for 30 min in the morning or instructed to sit in front of a desktop lighting device without light. The average level of motor activity during the night was significantly decreased in the bright light condition, compared with the controlled condition. However, daytime motor activity did not show significant differences between the two conditions. From these findings, even a short duration of morning bright light is effective in maintaining sleep without changing daytime activity.