Daytime Light Exposure Research Articles

Nighttime Insomnia Treatment and Education for Alzheimer's Disease: A Randomized, Controlled Trial

To evaluate whether a comprehensive sleep education program (Nighttime Insomnia Treatment and Education for Alzheimer's Disease (NITE-AD)) could improve sleep in dementia patients living at home with their family caregivers. A randomized, controlled trial. Thirty-six community-dwelling patients with Alzheimer's disease (AD) and their family caregivers. All participants received written materials describing age- and dementia-related changes in sleep and standard principles of good sleep hygiene. Caregivers in active treatment (n=17) received specific recommendations about setting up and implementing a sleep hygiene program for the dementia patient and training in behavior management skills. Patients in active treatment were also instructed to walk daily and increase daytime light exposure with the use of a light box. Control subjects (n=19) received general dementia education and caregiver support. Primary sleep outcomes were derived for patients and caregivers from 1 week of sleep-wake activity measured at baseline, posttest (2 months), and 6-month follow-up using an Actillume wrist-movement recorder. Secondary patient outcomes included the Epworth Sleepiness Scale, the Cornell Depression Scale, and the Revised Memory and Behavior Problem Checklist. Caregiver self-reports included the Pittsburgh Sleep Quality Index and the Center for Epidemiological Study of Depression Scale. Patients participating in NITE-AD showed significantly greater (P<.05) posttest reductions in number of nighttime awakenings, total time awake at night, and depression, and increases in weekly exercise days than control subjects. At 6-month follow-up, treatment gains were maintained, and additional significant improvements in duration of night awakenings emerged. When cognitive level was controlled, NITE-AD patients had lower longitudinal ratings of daytime sleepiness than controls. There was a trend for control subjects to spend more time in bed at 6 months than NITE-AD patients. This study provides the first evidence that patients with AD who are experiencing sleep problems can benefit from behavioral techniques (specifically, sleep hygiene education, daily walking, and increased light exposure) that are known to improve sleep in nondemented, institutionalized older adults.

Bright light effects at night and day on various measures of sleepiness

Objective: Nighttime bright light suppresses melatonin and reduces sleepiness. This reduction in sleepiness is associated with a reduction in the theta power of the Wake-EEG. Exogenous melatonin administration increases not only subjective sleepiness but also the theta power in the wake-EEG. This suggests that the reduction in sleepiness is mediated by melatonin. To test this we compared the activating properties of bright light exposure during nighttime with those during daytime, i.e. in the absence of melatonin. Methods and Material: A total number of 24 subjects participated in two experiments (N=12 each). All subjects were non-smoking healthy young males (age, mean±SD: 22,6±1.9 years). In the first experiment subjects were exposed to either bright light (5000 lux) or dim light <10 lux (control condition) between midnight and 4 a.m. In the second experiment subjects were exposed to either bright light or dim light between 12 a.m. and 4 p.m. Hourly measurements included salivary melatonin and cortisol concentrations, 6 minutes ECG, sleepiness (Karolinska Sleepiness Scale), and wake-EEG (3min with eyes closed). Effects of bright light were tested by repeated measurements ANOVAs for the 3 hours prior to light exposure against the three hours during light exposure. The measurements at lights-on were not included in this analysis. Results: Sleepiness (KSS) was significantly reduced in the ocular light condition independent whether light exposure took place during nighttime (F (11,1)=11.29, p<0.01) or daytime (F (11,1)=9.61, p=0.01). There was a significant (F (11,1)=31.20, p<0.001) melatonin suppression during nighttime light exposure whereas no melatonin was present, and suppressed during daytime. Heartrate increased (F (11,1)=22.92, p=0.001) and the variability in interbeat interval (F (11,1)=6.27, p=0.029) decreased significantly during nighttime but not during daytime exposure. Both during nighttime and during daytime light exposure there was no overall effect on the cortisol levels. Analysis of nighttime eyes closed wake-EEG revealed an increase in the power density in the theta frequency band with increasing duration of wakefulness which was significantly correlated with the increase of subjective sleepiness over time (r=0.43, p<0.001). During bright light exposure at night power density in the theta frequencies is lower than during the dim light condition (p<0.05) and this decrease was significantly correlated with the decrease in subjective sleepiness (Rs=0.65, p<0.05). Daytime bright light exposure had no effect on the theta frequency of the wake-EEG. Conclusions: Nighttime reduction of sleepiness by bright light is accompanied by physiological changes in melatonin, heart rate, theta frequency power density but not in cortisol. Daytime bright light exposure influences only sleepiness without a change in any of these physiological variables, which suggests that the reduction of sleepiness is not necessarily mediated through the suppression of melatonin. Subjective sleepiness at night seems to be related to the theta frequency in cortical wake EEG activity.

Illumination levels in nursing home patients: effects on sleep and activity rhythms.

Studies examining levels of illumination in adult populations have demonstrated that the level and amount of light exposure are lower in the elderly compared with younger adults, particularly in institutionalized patients with dementia. Although insufficient light exposure has been implied as a cause of sleep fragmentation, evidence for such a relationship is scant. Sixty-six institutionalized elderly had their activity and light exposure monitored for a 3-day period. Mean and median light levels, minutes spent over 1000 and over 2000 lux, percent sleep and wake, and number of naps were computed for daytime intervals, defined as 07.00-18.59. Percentages of sleep and wake, number of awakenings and mean duration of wake periods were computed for night-time intervals, defined as 22.00-05.59. Mesor, amplitude and acrophase of activity and of light were determined by cosinor analysis. A mixed linear model was used to assess the effects of daytime Actillume measures on subsequent night-time measures, and vice versa. Spearman correlations were computed, and multiple regression analyses were carried out with light variables and dementia level as predictors and sleep-wake and activity measures as dependent variables. The median light level was 54 lux and a median of only 10.5 min were spent over 1000 lux. Higher light levels predicted fewer night-time awakenings, and severe dementia predicted more daytime sleep and lower mean activity. Increased bright light exposure predicted later activity acrophase. There was an association between the acrophases of light and of activity, with maximum illumination preceding peak activity. These results suggest that daytime light exposure has an impact on both night-time sleep consolidation and timing of peak activity level.