Effect of short duration morning bright light in elderly men: sleep structure

The effects of daylight duration on the multiple sleep latency test (MSLT) results: A pilot study

OBJECTIVE

MSLT results are known to be affected by multiple factors including sleep time, frequency of nighttime arousals, and medications intake. Although being the main synchronizer of sleep and wakefulness, daylight duration effects on MSLT have not been examined. Burlington, Vermont, USA experiences great variations in daylight duration, ranging from 8 h 50 min to 15 h 33 min of daylight. The aim of this study was to test the hypothesis that there would be photoperiod duration effects on MSLTs performed during short daylight (short daylight studies, SDS) vs. long daylight (long daylight studies, LDS) from 2013 to 2023 in our sleep laboratory.

METHODS

We identified and analyzed 37 SDS (daylight 530-560 min) and 36 LDS (daylight 903-933 min) from our database. Groups of SDS and LDS results were compared using non-paired student T test, Chi-Square and non-parametric Mann Whitney U Test.

RESULTS

Average daylight duration was 15 h 18 ± 14.6 min for LDS and 8 h 57 ± 18 min for SDS. Two groups did not differ in terms of the age, gender, BMI and race of patients studied. Mean total sleep time and sleep efficiency during PSG preceding MSLT, and MSLT mean sleep onset latency did not significantly differ for the two groups. However, SDS MSLT naps had significantly more sleep onset REM periods (SOREMP), and distribution of the number of SOREMP captured during MSLT was different for SDS and LDS groups. Differences of SDS and LDS results did not relate to sleep architecture of the overnight PSG as analysis of sleep and REM latency and relative percentages of N1, N2, REM, and N3 was not significantly different between SDS and LDS. The two groups showed difference in arousal indexes during N1 and REM sleep.

CONCLUSIONS

Daylight duration may impact MSLT results and should probably be accounted for in MSLT interpretation. Attention to photoperiod could be considered in MSLT guidelines, if our results are replicated in larger samples.

[Effect of light therapy on the night sleep of children with sleep problems]

Effect of light therapy on the night sleep of children with sleep problems Abstract. Studies on the effect of light therapy on the nighttime sleep of adolescents revealed earlier sleep onset and longer sleep periods. The present study examines the corresponding effects in children. A group of 28 children (M = 10.0; SD = 1.65 years) with difficulties falling asleep and sleeping through the night received a light therapy device for home application. The effect was investigated by an A-B-A-B design with four measurement points. We detected significant, small- to medium-sized effects on the children's sleep-onset problems and ability to sleep through the night as well as mood. Sleep onset was reduced by approximately 10 minutes. The representativeness of the sample is limited, but the results largely correspond to the findings in adolescents. Because of the weekly switch between application and nonapplication, the true circadian effects might be underestimated. In principle, however, the effects found in adolescents appear to be transferable to children, though further research is necessary.

A systematic review of the amount and timing of light in association with objective and subjective sleep outcomes in community-dwelling adults

Light is considered the dominant environmental cue, or zeitgeber, influencing the sleep-wake cycle. Despite recognizing the importance of light for our well-being, less is known about the specific conditions under which light is optimally associated with better sleep. Therefore, a systematic review was conducted to examine the association between the amount and timing of light exposure in relation to sleep outcomes in healthy, community-dwelling adults. A systematic search was conducted of four databases from database inception to June 2016. In total, 45 studies met the review eligibility criteria with generally high study quality excepting for the specification of eligibility criteria and the justification of sample size. The majority of studies involved experimental manipulation of light (n = 32) vs observational designs (n = 13). Broad trends emerged suggesting that (1) bright light (>1000 lux) has positive implications for objectively assessed sleep outcomes compared to dim (<100 lux) and moderate light (100-1000 lux) and (2) bright light (>1000 lux) has positive implications for subjectively assessed sleep outcomes compared to moderate light (100-1000 lux). Effects due to the amount of light are moderated by the timing of light exposure such that, for objectively assessed sleep outcomes, brighter morning and evening light exposure are consistent with a shift in the timing of the sleep period to earlier and later in the day, respectively. For subjectively assessed sleep outcomes, brighter light delivered in the morning was associated with self-reported sleep improvements and brighter evening light exposure was associated with worse self-reported sleep.

Association of morning illumination and window covering with mood and sleep among post-menopausal women

The antidepressant and sleep-promoting effects of light exposure might be useful for treating age-related mood and sleep disorders. In view of recent evidence suggesting beneficial effects of morning light, this study examined the associations of mood and sleep with morning light exposure, 24 h environmental illumination, and the degree to which the volunteers' bedroom windows were covered in the morning. We examined 459 postmenopausal women participating an ancillary study of the Women's Health Initiative conducted at the University of California, San Diego Clinical Center, San Diego, CA, USA. At baseline, volunteers completed a 4-week sleep-recall questionnaire. Volunteers were then assessed for 5-7 days in their home environments with actigraphic wrist monitors. During home recording, self-reported mood was assessed. Morning illumination during the first 4 h after arising, 24-h illumination mesor (cosine-fitted mean), and illumination acrophase (cosine-fitted peak time) were calculated. Sleep was scored each night using validated wrist actigraphic methods. A sleep diary was completed each morning. During two 24-h periods, urine was collected approximately every 2 h during wakefulness and following any voidings during the sleep period. Cosine-fitting established the acrophase of urinary 6-sulfatoxymelatonin (aMT6s) excretion. Morning illumination and 24-h illumination were modestly associated with better mood and sleep. Associations of light with mood and sleep were consistently greater for subjects whose body clocks were delayed relative to the group median. Less morning window covering in the subjects' bedrooms was associated with more morning light and less depressed mood. The results suggest that both morning and 24-h light exposure may be beneficial for older adults.