Effect of exposure to evening light on sleep initiation in the elderly: A longitudinal analysis for repeated measurements in home settings

Daily light exposure profiles and the association with objective sleep quality in patients with Parkinson's disease: The PHASE study

STUDY OBJECTIVES

Light information crucially influences sleep initiation and continuity. The purpose of this study was to compare daily light exposure between patients with Parkinson's disease (PD) and non-PD older adults and evaluate the association of daily light exposure with objective sleep measures in patients with PD.

METHODS

In this cross-sectional study of 189 outpatients with PD and 1101 community-dwelling older adults (controls), daily light exposure was measured using wrist light meters during the daytime and light meters set in the bedrooms during the nighttime, and objective sleep quality was measured by wrist actigraphy.

RESULTS

The median duration of exposure to ≥ 1000 lux light was significantly shorter in patients with PD than in controls. The median nighttime light intensity was higher in patients with PD than in controls. Among patients with PD, multivariable analysis suggested that the highest quartile of exposure to ≥ 1000 lux light during the daytime was linked to significantly higher sleep efficiency (SE) by 8.0% and shorter wake after sleep onset (WASO) by 36.9 minutes than the lowest quartile. During the nighttime, the highest quartile of mean light intensity had significantly lower SE by 6.8%, longer WASO by 24.1 minutes, longer sleep onset latency, and higher fragmentation index, than the lowest quartile. Importantly, daytime and nighttime light levels were independently associated with objective sleep measures.

CONCLUSIONS

The present study illustrated that greater daytime light exposure and lower nighttime light exposure are significantly associated with better objective sleep measures in patients with PD.

Racial/ethnic and sex differences in the association between light at night and actigraphy-measured sleep duration in adults: NHANES 2011-2014

OBJECTIVE

Historically minoritized individuals experience greater exposure to light at night, yet it is unclear whether the association between light at night and sleep duration vary by race/ethnicity or sex. We examined the association between light at night and sleep duration by race/ethnicity and sex.

METHODS

Participants (N = 6089, mean age=49.5, 52% women, 13% Asian, 27% Black, 14% Mexican, 46% White) in the 2011-2014 National Health and Nutrition Examination Survey underwent 9-day of actigraphy. Light at night was defined as light exposure within the 5-hour activity nadir (L5). Sleep duration within a 24-hour period was analyzed as short (<7 hours) or long (>9 hours) compared to recommended (≥7 and <9 hours). Poisson models were fit to estimate the association between light at night and sleep duration after adjustment for covariates.

RESULTS

Light at night was most common among Black participants, who also had the shortest sleep duration. Overall, light at night was associated with 80% higher prevalence of short sleep duration [1.80 (1.49, 2.18)]. Compared to no-light at night, low and high light at night were associated with higher prevalence of short sleep duration, [1.61 (1.31, 1.98) and 2.01 (1.66, 2.44), respectively]. Associations varied by race/ethnicity and sex. Light at night was associated with shorter sleep duration in Black, Mexican and White females and Mexican and White males only. Black males exposed to light at night vs. no-light at night had lower prevalence of long sleep duration. There were no associations between light at night and sleep duration among Asian participants.

CONCLUSION

Light at night was associated with shorter sleep duration, particularly among females. Targeting light exposure may help to improve sleep duration.

Night-to-night associations between light exposure and sleep health

Previous research has demonstrated that exposure to light preceding and during sleep is associated with poor sleep, but most research to date has utilized either experimental or cross-sectional designs. The current study expands upon prior studies by using a microlongitudinal design that examines the night-to-night associations between light and sleep health in a diverse sample of adults (pre-registered at osf.io/k5zgv). US adults aged 18-87 years from two parent studies (N = 124) wore an actiwatch for up to 10 nights. Light variables estimated from actigraphy include both average exposure and time above light threshold of 10 (TALT10 ) and 40 (TALT40 ) lux both during sleep and for the 1-hr preceding sleep. Actigraphy-based sleep variables included sleep offset, duration, percentage and fragmentation index. Higher average light exposure during sleep was associated with a later sleep-offset time, lower sleep percentage and higher fragmentation index (all p < 0.01). More minutes of TALT10 during sleep was associated with later sleep timing, lower sleep percentage and higher fragmentation index (all p < 0.01), and greater TALT40 during sleep was associated with lower sleep percentage. Light exposure was not related to sleep duration. In summary, greater light exposure during sleep was related to poorer sleep continuity and later wake time. The lack of association between light and sleep duration may be the result of compensating for sleep disruption by delaying wake time. Multi-level interventions to consistently reduce light levels during sleep should be considered.

Circadian rhythms as modulators of brain health during development and throughout aging

The circadian clock plays a prominent role in neurons during development and throughout aging. This review covers topics pertinent to the role of 24-h rhythms in neuronal development and function, and their tendency to decline with aging. Pharmacological or behavioral modification that augment the function of our internal clock may be central to decline of cognitive disease and to future chronotherapy for aging-related diseases of the central nervous system.

Understanding the determinants of circadian health disparities and cardiovascular disease

Emerging research suggests that sleep contributes to racial disparities in cardiovascular disease (CVD). Racial/ethnic minorities are disproportionately affected by poor cardiovascular outcomes including obesity, hypertension and diabetes. Although circadian rhythms affect sleep patterns, few studies have examined disparities in circadian health or the contribution of circadian disparities to CVD. In this paper, we provide an overview of the relation between circadian health and CVD in the context of health disparities. We discuss (1) the current knowledge on racial disparities in circadian health; (2) social and environmental determinants of circadian health disparities; (3) the cardiovascular consequences of circadian disparities; and (4) future opportunities to advance the field of circadian disparities. In brief, our findings demonstrated that among a small literature, racial minorities (mainly African American) were more likely to have a shorter circadian period, delayed phase shifts, and were more likely to be shift workers, which are associated with CVD risk factors. Given racial minorities are disproportionately affected by CVD and CVD risk factors, it is important to further understand circadian health as an intervention target and support more research among racial minorities to understand circadian health in these populations.

Association of physical activity, sedentary behaviour, and daylight exposure with sleep in an ageing population: findings from the Whitehall accelerometer sub-study

BACKGROUND

Ageing is accompanied by changes in sleep, while poor sleep is suggested as a risk factor for several health outcomes. Non-pharmacological approaches have been proposed to improve sleep in elderly; their impact remains to be investigated. The aim of this study was to examine the independent day-to-day associations of physical behaviours and daylight exposure with sleep characteristics among older adults.

METHODS

Data were drawn from 3942 participants (age range: 60-83 years; 27% women) from the Whitehall II accelerometer sub-study. Day-to-day associations of objectively-assessed daytime physical behaviours (sedentary behaviour, light-intensity physical activity (LIPA), moderate-to-vigorous physical activity (MVPA), mean acceleration, physical activity chronotype) and daylight exposure (proportion of waking window with light exposure > 1000 lx and light chronotype) with sleep characteristics were examined using mixed models.

RESULTS

A 10%-increase in proportion of the waking period spent sedentary was associated with 5.12-minute (4.31, 5.92) later sleep onset and 1.76-minute shorter sleep duration (95%confidence interval: 0.86, 2.66). Similar increases in LIPA and MVPA were associated with 6.69 (5.67, 7.71) and 4.15 (2.49, 5.81) earlier sleep onset respectively and around 2-minute longer sleep duration (2.02 (0.87, 3.17) and 2.23 (0.36, 4.11), respectively), although the association was attenuated for MVPA after adjustment for daylight exposure (1.11 (- 0.84, 3.06)). A 3-hour later physical activity chronotype was associated with a 4.79-minute later sleep onset (4.15, 5.43) and 2.73-minute shorter sleep duration (1.99, 3.47). A 10%-increase in proportion of waking period exposed to light> 1000 lx was associated with 1.36-minute longer sleep (0.69, 2.03), independently from mean acceleration. Associations found for sleep duration were also evident for duration of the sleep windows with slightly larger effect size (for example, 3.60 (2.37, 4.82) minutes for 10%-increase in LIPA), resulting in associations with sleep efficiency in the opposite direction (for example, - 0.29% (- 0.42, - 0.16) for 10%-increase in LIPA). Overall, associations were stronger for women than for men.

CONCLUSIONS

In this study, higher levels of physical activity and daylight exposure were associated with slightly longer sleep in older adults. Given the small effect sizes of the associations, increased physical activity and daylight exposure might not be enough to improve sleep.

Multidimensional Environmental Factors and Sleep Health for Aging Adults: A Focused Narrative Review

The timing, amount, and quality of sleep are critical for an individual's health and quality of life. This paper provides a focused narrative review of the existing literature around multidimensional environments and sleep health for aging adults. Five electronic databases, Scopus, Web of Science, PubMed/Medline; EBSCOhost, PsycINFO (ProQuest), and Google Scholar yielded 54,502 total records. After removing duplicates, non-peer reviewed academic articles, and nonrelevant articles, 70 were included for review. We were able to categorize environmental factors into housing security, home environment, and neighborhood environment, and, within each environmental category, specific elements/aspects are discussed. This paper provides a comprehensive map connecting identified levels of influence (individual, home/house, and neighborhood-level) in which subfactors are listed under each level of influence/category with the related literature list. Our review highlights that multidimensional environmental factors can affect aging adults' sleep health and eventually their physical, mental, and cognitive health and that sleep disparities exist in racial minorities in socioeconomically disadvantaged communities in which cumulative environmental stressors coexist. Based on this focused narrative review on the multidimensional sleep environments for aging adults, knowledge gaps are identified, and future research directions are suggested.

Association of perceptions of artificial light-at-night, light-emitting device usage and environmental noise appraisal with psychological distress, sleep quality and chronotype: A cross sectional study

Exposure to artificial light-at-night (ALAN) is increasing globally, and there are concerns around how ALAN may impact sleep, psychological and physical health. However, there is a lack of evidence in the literature on how individuals perceive ALAN relative to their sleeping environment and habits, and how such perceptions correspond to objectively assessed night-time illuminance at the level of the residence. This cross-sectional study examined how such perceptions associate with sleep quality, sleep timing, psychological distress and cognitive failures. Further we examined the association between illuminance levels calculated as the biologically-relevant melatonin-suppression index (MSI) and the self-report of perception of ALAN. Five hundred and fifty two adult participants completed a survey addressing perception of ALAN in sleep environment along with the Pittsburgh Sleep Quality Index, Munich Chronotype Questionnaire, Cognitive Failure Questionnaire and the General Health Questionnaire. We report that perception of external ALAN in the sleeping environment was associated with poorer sleep quality, more cognitive failures and greater psychological distress, when controlling for age, sex, house location and MSI. No associations were found between the perception of external ALAN and MSI scores, and MSI scores were not associated with scores on any of the self-report measures. Internal lighting passing into the sleeping environment was associated with poorer sleep quality but not with psychological wellbeing. Habitual use of light-emitting devices was associated with poorer psychological wellbeing but not with sleep quality and sleep timing. Perception of environmental noise annoyance at night was associated with higher psychological distress and poorer quality sleep, and the perception of noise annoyance was associated with perception of ALAN. These results may suggest heightened attentional bias towards ALAN associated with poor sleep quality and higher levels of psychological distress, and highlight the need for more granular approaches in the study of ALAN and sleep and psychological health in terms of levels individual ALAN exposure, and an interpretation that seeks to integrate biological and psychological perspectives.

The Effect of Light Therapy on Electroencephalographic Sleep in Sleep and Circadian Rhythm Disorders: A Scoping Review

Light therapy is used to treat sleep and circadian rhythm disorders, yet there are limited studies on whether light therapy impacts electroencephalographic (EEG) activity during sleep. Therefore, we aimed to provide an overview of research studies that examined the effects of light therapy on sleep macro- and micro-architecture in populations with sleep and circadian rhythm disorders. We searched for randomized controlled trials that used light therapy and included EEG sleep measures using MEDLINE, PubMed, CINAHL, PsycINFO and Cochrane Central Register of Controlled Trials databases. Five articles met the inclusion criteria of patients with either insomnia or delayed sleep−wake phase disorder (DSWPD). These trials reported sleep macro-architecture outcomes using EEG or polysomnography. Three insomnia trials showed no effect of the timing or intensity of light therapy on total sleep time, wake after sleep onset, sleep efficiency and sleep stage duration compared to controls. Only one insomnia trial reported significantly higher sleep efficiency after evening light therapy (>4000 lx between 21:00−23:00 h) compared with afternoon light therapy (>4000 lx between 15:00−17:00 h). In the only DSWPD trial, six multiple sleep latency tests were conducted across the day (09:00 and 19:00 h) and bright light (2500 lx) significantly lengthened sleep latency in the morning (09:00 and 11:00 h) compared to control light (300 lx). None of the five trials reported any sleep micro-architecture measures. Overall, there was limited research about the effect of light therapy on EEG sleep measures, and studies were confined to patients with insomnia and DSWPD only. More research is needed to better understand whether lighting interventions in clinical populations affect sleep macro- and micro-architecture and objective sleep timing and quality.

The Relationship Between Light Exposure before Bedtime and Daytime Sleepiness Among People Living With Cognitive Impairment

While sleep disturbances are common in people living with cognitive impairment, little is known about the influence of evening light exposure on their sleep. The purpose of this study was to examine the relationship between evening light exposure in natural living environment and daytime sleepiness in community residing people living with cognitive impairment. A secondary data analysis was conducted using the baseline data of the Healthy Patterns Clinical Trial. Actiwatch Spectrum Plus was used to collect information on the average white light intensity of 4 hours before sleep for three consecutive days. Multivariate regression analyses were used. Among 173 participants, the average light intensity during evening was 80.25 ± 123.04 lux. After controlling for covariates, greater intensity of light exposure during evening was related to excessive daytime sleepiness (β = 0.211, p = .004). The results of our study suggest exposure to light during evening may disturb sleep and subsequently influence daytime sleepiness the following day.

Effect of nighttime bedroom light exposure on mood episode relapses in bipolar disorder

OBJECTIVE

A previous cross-sectional study reported that nighttime light is associated with increased occurrence of manic symptoms in bipolar disorder; however, the longitudinal association between nighttime light and subsequent mood episode relapses remains unclear. We determined whether bedroom nighttime light was associated with mood episode relapses in patients with bipolar disorder.

METHODS

This prospective cohort study included 172 outpatients with bipolar disorder who participated in an Association between the Pathology of Bipolar Disorder and Light Exposure in Daily Life (APPLE) cohort study. A portable photometer was used to measure illuminance in the bedroom from bedtime to rising time during 7 consecutive nights for baseline assessment. Then, the participants were assessed at a 2-year follow-up for mood episode relapses.

RESULTS

Of the 172 participants, 157 (91%) completed the 2-year follow-up, and 39 (22%) experienced manic or hypomanic episodes (with or without mixed features), during that time. In the Cox proportional-hazards model, the hazard ratio (HR) for manic/hypomanic episode relapses was significantly higher when the average nighttime illuminance was ≥3 lux (n = 71) than when it was <3 lux (n = 101; HR, 2.54; 95% confidence interval (CI), 1.33-4.84). In the multivariable model adjusted for a propensity score in relation to nighttime light, the relationship remained significant (HR, 2.17; 95% CI, 1.04-4.52). The association between nighttime light and depressive episode relapses was not significantly different.

CONCLUSIONS

Keeping the bedroom dark at night may prevent hypomanic and manic episodes.

A longitudinal study of morning, evening, and night light intensities and nocturnal sleep quality in a working population

We aimed to investigate whether higher light intensity in the morning is associated with better nocturnal sleep quality and whether higher light intensities in the evening or night have the opposite effect. Light intensity was recorded for 7 consecutive days across the year among 317 indoor and outdoor daytime workers in Denmark (55-56° N) equipped with a personal light recorder. Participants reported sleep quality after each nocturnal sleep. Sleep quality was measured using three parameters; disturbed sleep index, awakening index, and sleep onset latency. Associations between increasing light intensities and sleep quality were analyzed using mixed effects models with participant identity as a random effect. Overall, neither white nor blue light intensities during morning, evening, or night were associated with sleep quality, awakening, or sleep onset latency of the subsequent nocturnal sleep. However, secondary analyses suggested that artificial light during the morning and day contrary to solar light may increase vulnerability to evening light exposure. Altogether, we were not able to confirm that higher morning light intensity significantly improves self-reported sleep quality or that higher evening or night light intensities impair self-reported sleep quality at exposure levels encountered during daily life in a working population in Denmark. This suggests that light intensities alone are not important for sleep quality to a degree that it is distinguishable from other important parameters in daily life settings.

Nighttime Light Hurts Mammalian Physiology: What Diurnal Rodent Models Are Telling Us

Natural sunlight permits organisms to synchronize their physiology to the external world. However, in current times, natural sunlight has been replaced by artificial light in both day and nighttime. While in the daytime, indoor artificial light is of lower intensity than natural sunlight, leading to a weak entrainment signal for our internal biological clock, at night the exposure to artificial light perturbs the body clock and sleep. Although electric light at night allows us "to live in darkness", our current lifestyle facilitates nighttime exposure to light by the use, or abuse, of electronic devices (e.g., smartphones). The chronic exposure to light at nighttime has been correlated to mood alterations, metabolic dysfunctions, and poor cognition. To decipher the brain mechanisms underlying these alterations, fundamental research has been conducted using animal models, principally of nocturnal nature (e.g., mice). Nevertheless, because of the diurnal nature of human physiology, it is also important to find and propose diurnal animal models for the study of the light effects in circadian biology. The present review provides an overview of the effects of light at nighttime on physiology and behavior in diurnal mammals, including humans. Knowing how the brain reacts to artificial light exposure, using diurnal rodent models, is fundamental for the development of new strategies in human health based in circadian biology.

Effect of COVID-19-Related Home Confinement on Sleep Quality, Screen Time and Physical Activity in Tunisian Boys and Girls: A Survey

COVID-19 home confinement has led to a stressful situation for children around the world and affected their lifestyle. The present study aimed to investigate the effect of these restrictions on sleep quality, screen time (ST) and physical activity (PA) in Tunisian children with a special focus on gender differences. An online survey was launched in April 2020. Questions were presented in a differential format, with expected responses related to "before" and "during" confinement. Participants (52 boys and 48 girls, age: 8.66 ± 3.3 years) responded to the Pittsburgh Sleep Quality Index (PSQI), the digital media use, and the Ricci and Gagnon sedentary behavior questionnaires. Findings revealed that COVID19 home confinement had a negative effect on all the considered parameters (p < 0.05). Significant effects of gender were found on sleep disturbances (p = 0.016, np2 = 0.05), subjective sleep quality (p < 0.01, np2 = 0.07), global score of PSQI (p = 0.01, np2 = 0.01) and nocturnal and global screen time (p < 0.001, np2 = 0.09) with poorer sleep and higher screen time in girls compared to boys during home confinement. A significant correlation was shown between Global ST and PSQI score (r = 0.39, p < 0.001). Programs of PA for children and sensitization campaigns against the use of screens have been deemed urgent with special focus oriented to girls.

Effect of evening light exposure on sleep in bipolar disorder: A longitudinal analysis for repeated measures in the APPLE cohort

OBJECTIVE

Sleep disturbance, a core feature of bipolar disorder, is associated with residual mood symptoms, mood episode recurrence and suicide ideation. We investigated the effect of evening light exposure on sleep in patients with bipolar disorder.

METHODS

In this longitudinal analysis, we measured the sleep parameters of 207 outpatients with bipolar disorder using actigraphy at their homes for seven consecutive nights. We measured the white-light illuminance and the irradiance of each wavelength during the 4 hours before each participant's bedtime. We used mixed-effect linear regression analysis for repeated measures to evaluate the effect of evening light exposure on subsequent sleep parameters.

RESULTS

The median white-light illuminance was 25.8 lux (interquartile range, 12.9-50.1 lux). In a multivariable model adjusted for potential confounders, we found higher white-light illuminance to be significantly associated with lower sleep efficiency (per log lux: 95% confidence interval = [-1.328, -0.133]; p = 0.017), prolonged sleep-onset latency (95% confidence interval = [0.006, 0.172]; p = 0.035) and longer wake after sleep onset (95% confidence interval = [1.104, 4.459]; p = 0.001). This effect size was larger in the younger age group (aged < 44 years) stratified by median age. Higher irradiance of the blue wavelength range was significantly associated with longer wake after sleep onset, a result similar to those for the green and red wavelength ranges.

CONCLUSION

We observed significant associations between evening light exposure and subsequent sleep in patients with bipolar disorder. The effects of various light wavelengths on sleep in bipolar disorder require further investigation.

Lighting in the Home and Health: A Systematic Review

Poor housing is an important determinant of poor health. One key aspect of housing quality is lighting. Light is important for visual performance and safety, and also plays a vital role in regulating human physiological functions. This review aims to synthesise existing evidence on the relationship between lighting in the home and health and recommends areas for future research. Three databases were searched for relevant literature using pre-defined inclusion criteria. Study quality was assessed using the Newcastle Ottawa Scale. Extracted data were qualitatively synthesised according to type of lighting (natural light, artificial light and light at night) and stratified by broad health domains (physical, mental and sleep health). Of the 4043 records retrieved, 28 studies met the inclusion criteria. There was considerable heterogeneity in light exposure metrics used and specific health outcome assessed by the studies. Lighting in the home can negatively affect health but the current evidence base is limited to a small number of studies in different domains of light and health. Further research surrounding specific health outcomes is required to better inform housing quality assessments and lighting practises in the home.

Is night-time light intensity associated with cardiovascular disease risk factors among adults in early-stage urbanisation in South India? A cross-sectional study of the Andhra Pradesh Children and Parents Study

OBJECTIVES

To explore associations of night-time light intensity (NTLI), a novel proxy for continuous urbanisation levels, with mean systolic blood pressure (SBP), body mass index (BMI), fasting serum low-density lipoprotein (LDL) and fasting plasma glucose (FPG), among adults in early-stage urbanisation in Telangana, South India.

DESIGN

Cross-sectional analysis of the third wave of the Andhra Pradesh Children and Parents Study cohort.

SETTING

28 villages representing a continuum of urbanisation levels, ranging from rural settlement to medium-sized town in Telangana, South India.

PARTICIPANTS

Data were available from 6944 participants, 6236 of whom were eligible after excluding pregnant women, participants younger than 18 years of age and participants missing data for age. Participants were excluded if they did not provide fasting blood samples, had implausible or missing outcome values, were medicated for hypertension or diabetes or had triglyceride levels invalidating derived LDL. The analysis included 5924 participants for BMI, 5752 participants for SBP, 5287 participants for LDL and 5328 participants for FPG.

RESULTS

Increasing NTLI was positively associated with mean BMI, SBP and LDL but not FPG. Adjusted mean differences across the range of village-level NTLI were 1.0 kg/m2 (95% CI 0.01 to 1.9) for BMI; 4.2 mm Hg (95% CI 1.0 to 7.4) for SBP; 0.3 mmol/L (95% CI -0.01 to 0.7) for LDL; and -0.01 mmol/L (95% CI -0.4 to 0.4) for FPG. Associations of NTLI with BMI and SBP were stronger in older age groups.

CONCLUSION

The association of NTLI with cardiovascular disease (CVD) risk factors identify NTLI as a potentially important tool for exploring urbanisation-related health. Consistent associations of moderate increases in urbanisation levels with important CVD risk factors warrant prevention strategies to curb expected large public health impacts from continued and rapid urbanisation in India.

Analysis of the evidence of related factors, associated conditions and at-risk populations of the NANDA-I nursing diagnosis insomnia

Objectives

To summarize evidence in the literature on the predictors of insomnia in adults and to determine correspondences with diagnostic indicators of the NANDA-I diagnosis Insomnia.

Methods

An integrative review performed in Pubmed, Virtual Health Library and CINAHL. Forty-eight articles published in Portuguese, English or Spanish from 2011 to 2018 were included. An analysis of correspondence between the predictors and the NANDA-I related factors and associated conditions for Insomnia was performed.

Results

There was a correspondence of the predictors found in this review with NANDA-I related factors and associated conditions, except for grieving and frequent naps during the day. Smoking, caffeine intake, dysfunctional sleep beliefs, obesity and caregiver role strain are possible new related factors; chronic illness is a possible new associated condition and individuals going through changes in marital status, economically disadvantaged, female gender, increasing age and night shift worker are possible new at-risk populations.

Conclusion

The predictors of insomnia that had a correspondence with the NANDA-I elements can support the evidence base of the nursing diagnosis. The predictors found without a correspondence with the diagnosis can be considered for inclusion in the NANDA-I classification, thereby supporting the clinical reasoning of nurses and students.

Perceptions of Light Pollution and its Impacts: Results of an Irish Citizen Science Survey

BACKGROUND

Light pollution is increasingly an area of concern for health and quality of life research. Somewhat surprisingly, there are relatively few descriptions of perceptions of light pollution in the literature. The current study examined such perceptions in a Irish sample.

METHODS

A survey was circulated as part of a citizen science initiative of a national newspaper; the survey included questions regarding night sky brightness and the impact of light at night on sleep and animal behaviour. Complete responses from 462 respondents were analysed.

RESULTS

Urban location was, as anticipated, associated with reported brighter night skies, and public lighting was reported as the main source of light at night for urban settings, whilst neighbours' domestic lighting was the most commonly reported source for rural settings. Respondents from rural settings were more likely to report that light at night impinged on sleep, whilst city dwellers were more likely to report recent changes in wildlife behaviour.

CONCLUSIONS

Citizen science approaches may be useful in gathering data on public perceptions of light pollution and its impacts. In the current study, this perception was strongly influenced by location, highlighting the importance of assessing experiences and attitudes across a number of geographical settings.

Interventions to reduce short-wavelength ("blue") light exposure at night and their effects on sleep: A systematic review and meta-analysis

The sleep-wake and circadian cycles are influenced by light, particularly in the short-wavelength portion of the visible spectrum. Most personal light-emitting electronic devices are enriched in this so-called "blue" light. Exposure to these devices in the evening can disturb sleep. Interventions to reduce short-wavelength light exposure before bedtime may reduce adverse effects on sleep. We conducted a systematic review and meta-analysis to examine the effect of wearing color-tinted lenses (e.g. orange or amber) in frames to filter short-wavelength light exposure to the eye before nocturnal sleep. Outcomes were self-reported or objective measures of nocturnal sleep. Relatively few (k = 12) studies have been done. Study findings were inconsistent, with some showing benefit and others showing no effect of intervention. Meta-analyses yielded a small-to-medium magnitude combined effect size for sleep efficiency (Hedge's g = 0.31; 95% CI: -0.05, 0.66; I2 = 38.16%; k = 7), and a small-to-medium combined effect size for total sleep time (Hedge's g = 0.32; 95% CI: 0.01, 0.63; I2 = 12.07%; k = 6). For self-report measures, meta-analysis yielded a large magnitude combined effects size for Pittsburgh Sleep Quality Index ratings (Hedge's g = -1.25; 95% CI: -2.39, -0.11; I2 = 36.35%; k = 3) and a medium combined effect size for total sleep time (Hedge's g = 0.51; 95% CI: 0.18, 0.84; I2 = 0%; k = 3), Overall, there is some, albeit mixed, evidence that this approach can improve sleep, particularly in individuals with insomnia, bipolar disorder, delayed sleep phase syndrome, or attention-deficit hyperactive disorder. Considering the ubiquitousness of short-wavelength-enriched light sources, future controlled studies to examine the efficacy of this approach to improve sleep are warranted. Systematic review registration: PROSPERO 2018 CRD42018105854.

How Much Lighting is Required to Feel Safe When Walking Through the Streets at Night?

Public space lighting (PSL) is indispensable after the natural dark. However, little is known about how much PSL people actually need to feel sufficiently safe in different real-world urban settings. The present study attempts to answer this question by employing a novel real-time interactive approach, according to which, observers use a specially-designed mobile phone application to assess and report the perceived attributes of street lighting and the feeling of safety (FoS) it generates. To validate the proposed approach, a systematic survey was conducted in three cities in Israel—Tel Aviv-Yafo and Haifa, which lie on the Mediterranean coast, and Be’er Sheba, which lies inland. Additionally, instrumental PSL measurements were performed at the same locations. As the study reveals, the necessary level of illumination required by urban residents to feel safe differs by city and is significantly higher in Be’er Sheba, other factors held equal, in compare to Haifa and Tel Aviv-Yafo. This difference may be attributed to stronger daylight that the residents of the desert city of Be’er Sheba are accustomed to, and, therefore, may prefer stronger nighttime illumination. The difference could also be related to the relatively low socio-economic status and somewhat higher crime rates in the latter city. Findings also show a significant and positive association between FoS and instrumentally measured PSL levels, although this association exhibits diminishing returns. To the best of our knowledge, the present study is the first to use an interactive location- and time-based mobile phone technology, which can potentially provide more accurate and reliable assessments, compared to traditional “pen and paper” survey techniques.

Sex and estrous cycle dependent changes in locomotor activity, anxiety and memory performance in aged mice after exposure of light at night

Light-at-night (LAN) can affect mammalian behaviour. But, the effects of LAN on aged rodents remain undefined yet. In the present investigation, aged Swiss Albino mice, habituated in regular light-dark cycle, were exposed to bright-light-pulse (1-h) at night on the day of study followed by experimentations for assessment of locomotor activities in the open field, anxiety in the elevated plus maze and short-term memory for novel object recognition (NOR) in the habituated field. Under without-bright-light exposure, (a) aged proestrous females showed greater locomotor activities and less anxiety than in aged diestrous females, (b) aged males showed locomotor activities and anxiety level similar to aged diestrous females and aged proestrous females respectively and (c) all animals failed to retain in object discrimination memory. LAN exposure exhibited the continual failure of such retention of memory while animals showed free and spontaneous exploration with thigmotactic behaviour having no object bias and/or phobia, but time stay in objects by animals altered variably among sexes and stages of estrous cycle. Overall, the LAN caused (a) diminution in locomotor activities, rise in anxiety and failure of memory for recognition of both familiar and novel objects in aged proestrous females, (b) hyperlocomotor activities and reduction in anxiety in both males and diestrous females with the failure of memory for recognition of novel objects only in aged males while diestrous females showed enhanced exploration time to both objects during NOR. Thus, nocturnal behaviour of aged mice varies with sex and estrous cycle and light acts differentially on them.

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.

Pre-awake light exposure and sleep disturbances: findings from the HEIJO-KYO cohort

OBJECTIVES

To evaluate the associations between pre-awake light (PAL) exposure and subjective and objective measures of sleep quality.

METHODS

In this cross-sectional study of 1108 elderly participants (mean age, 71.9 years), we measured bedroom light intensity using a bedside light meter for two nights and sleep quality using actigraphy and a questionnaire. PAL was determined as the 2h-average light intensity before rise time, and sleep disturbance was defined as the Pittsburgh sleep quality index score ≥6.

RESULTS

Sleep disturbance prevalence increased with increased PAL exposure (P = 0.002). In multivariable models adjusted for potential confounders, the odds ratio (OR) for sleep disturbances was significantly higher in the highest quartile PAL group (Q4) than in the lowest quartile group (Q1) (OR, 1.65; 95% CI, 1.16-2.34). This association occurred independent of post-bedtime light exposure; and was stronger in the later chronotype group (n = 556) (OR, 1.80; 95% CI, 1.05-3.09) than in the earlier chronotype group (n = 552) (OR, 1.64; 95% CI, 1.01-2.64). Actigraphic sleep efficiency in the Q4 group was significantly lower by 2.6% (95% CI, 1.3-3.8) than that in the Q1 group. Moreover, longer wake after sleep onset by 7.5 min (95% CI, 2.8-12.2) and sleep onset latency by 0.2 log min (95% CI, 0.1-0.4) were observed in the Q4 group than the Q1 group.

CONCLUSIONS

Higher PAL exposure was significantly associated with a higher prevalence of sleep disturbances, independent of post-bedtime light exposure. Consistent results were observed in the actigraphy analysis.

Sleep Environment and Insomnia in Elderly Persons Living at Home

The aim of this study was to draw a portrait of the sleep environment of elderly persons living in private households and to determine its relationship with the presence of insomnia. A sample of 599 individuals aged 70 years and older responded to questions about the comfort of their pillow and mattress and the noise level and brightness of their bedroom at night and in the morning. They were also asked whether or not they shared their bed or bedroom with a sleep partner. The Insomnia Severity Index was used to assess insomnia severity. Over 40% of the study participants were using a pillow that was not very comfortable, and almost 30% said that their bedroom was not completely quiet. Binomial logistic regression results revealed that two variables were significantly associated with insomnia symptoms: a pillow rated as moderately comfortable to very uncomfortable and a bedroom that was not completely quiet. No other sleep environment characteristics considered in this study were associated with the risk of insomnia. These results indicate that a nonnegligible proportion of the elderly population endures a suboptimal sleep environment. Although it is difficult to predict the real impact of changes to the sleep environment, this study supports the proposal that simple, minor changes to the bedroom can promote sleep in the elderly.

Population-level study links short-wavelength nighttime illumination with breast cancer incidence in a major metropolitan area

Several population-level studies revealed a positive association between breast cancer (BC) incidence and artificial light at night (ALAN) exposure. However, the effect of short-wavelength illumination, implicated by laboratory research and small-scale cohort studies as the main driving force behind BC-ALAN association, has not been supported by any population-level study carried out to date. We investigated a possible link between BC and ALAN of different subspectra using a multi-spectral year-2011 satellite image, taken from the International Space Station, and superimposing it with year-2013 BC incidence data available for the Great Haifa Metropolitan Area in Israel. The analysis was performed using both ordinary least square (OLS) and spatial dependency models, controlling for socioeconomic and locational attributes of the study area. The study revealed strong associations between BC and blue and green light subspectra (B = 0.336 ± 0.001 and B = 0.335 ± 0.002, respectively; p < 0.01), compared to a somewhat weaker effect for the red subspectrum (B = 0.056 ± 0.001; p < 0.01). However, spatial dependency models, controlling for spatial autocorrelation of regression residuals, confirmed only a positive association between BC incidence and short-wavelength (blue) ALAN subspectrum (z = 2.462, p < 0.05) while reporting insignificant associations between BC and either green (z = 1.425, p > 0.1) or red (z = -0.604, p > 0.1) subspectra. The obtained result is in line with the results of laboratory- and small-scale cohort studies linking short-wavelength nighttime illumination with circadian disruption and melatonin suppression. The detected effect of blue lights on BC incidence may help to develop informed illumination policies aimed at minimizing the adverse health effects of ALAN exposure on human health.

Bedroom Light Exposure at Night and the Incidence of Depressive Symptoms: A Longitudinal Study of the HEIJO-KYO Cohort

Previous studies have indicated that minimal exposure to light at night (LAN) increases depression risk, even at 5 lux, in nocturnal and diurnal mammals. Although such low-level LAN may affect human circadian physiology, the association between exposure to LAN and depressive symptoms remains uncertain. In the present study, bedroom light intensity was measured objectively, and depressive symptoms were assessed, during 2010-2014 in Nara, Japan. Of 863 participants (mean age = 71.5 years) who did not have depressive symptoms at baseline, 73 participants reported development of depressive symptoms during follow-up (median, 24 months). Compared with the "dark" group (average of <5 lux; n = 710), the LAN group (average of ≥5 lux; n = 153) exhibited a significantly higher depression risk (hazard ratio = 1.89; 95% CI: 1.13, 3.14), according to a Cox proportional hazards model adjusting for age, sex, body mass index, and economic status. Further, the significance remained in a multivariable model adjusting for hypertension, diabetes, and sleep parameters (hazard ratio = 1.72; 95% CI: 1.03, 2.89). Sensitivity analyses using bedroom light data with a cutoff value of ≥10 lux suggested consistent results. In conclusion, these results indicated that exposure to LAN in home settings was independently associated with subsequent depression risk in an elderly general population.

Environmental Design for End-of-Life Care: An Integrative Review on Improving the Quality of Life and Managing Symptoms for Patients in Institutional Settings

CONTEXT

The environment in which end-of-life (EOL) care is delivered can support or detract from the physical, psychological, social, and spiritual needs of patients, their families, and their caretakers.

OBJECTIVES

This review aims to organize and analyze the existing evidence related to environmental design factors that improve the quality of life and total well-being of people involved in EOL care and to clarify directions for future research.

METHODS

This integrated literature review synthesized and summarized research evidence from the fields of medicine, environmental psychology, nursing, palliative care, architecture, interior design, and evidence-based design.

RESULTS

This synthesis analyzed 225 documents, including nine systematic literature reviews, 40 integrative reviews, three randomized controlled trials, 118 empirical research studies, and 55 anecdotal evidence. Of the documents, 192 were peer-reviewed, whereas 33 were not. The key environmental factors shown to affect EOL care were those that improved 1) social interaction, 2) positive distractions, 3) privacy, 4) personalization and creation of a home-like environment, and 5) the ambient environment. Possible design interventions relating to these topics are discussed. Examples include improvement of visibility and line of sight, view of nature, hidden medical equipment, and optimization of light and temperature.

CONCLUSION

Studies indicate several critical components of the physical environment that can reduce total suffering and improve quality of life for EOL patients, their families, and their caregivers. These factors should be considered when making design decisions for care facilities to improve physical, psychological, social, and spiritual needs at EOL.

Influence of Day Length and Physical Activity on Sleep Patterns in Older Icelandic Men and Women

STUDY OBJECTIVES

To identify cross-sectional and seasonal patterns of sleep and physical activity (PA) in community-dwelling, older Icelandic adults using accelerometers.

METHODS

A seven-day free-living protocol of 244 (110 female) adults aged 79.7 ± 4.9 years was conducted as part of a larger population-based longitudinal observational-cohort study in the greater Reykjavik area of Iceland. A subpopulation (n = 72) repeated the 7-day measurement during seasonal periods with greater (13.4 ± 1.4 h) and lesser (7.7 ± 1.8 h) daylight.

RESULTS

Cross-sectional analyses using multiple linear regression models revealed that day length was a significant independent predictor of sleep duration, mid-sleep, and rise time (all p < 0.05). However, the actual within-individual differences in sleep patterns of the repeaters were rather subtle between periods of longer and shorter day-lengths. Compared to women, men had a shorter sleep duration (462 ± 80 vs. 487 ± 68 minutes, p = 0.008), earlier rise time, and a greater number of awakenings per night (46.5 ± 18.3 vs. 40.2 ± 15.7, p = 0.007), but sleep efficiency and onset latency were similar between the two sexes. Daily PA was also similar between men and women and between periods of longer and shorter day-lengths. BMI, age, gender, and overall PA all contributed to the variations in sleep parameters using multiple regression analysis.

CONCLUSIONS

The sleep and PA characteristics of this unique population revealed some gender differences, but there was limited variation in response to significant daylight changes which may be due to long-term adaptation.

Ambient Light Exposure and Changes in Obesity Parameters: A Longitudinal Study of the HEIJO-KYO Cohort

CONTEXT

Previous epidemiological studies have suggested an association between nighttime light levels and the prevalence of obesity, although evidence is limited to cross-sectional studies.

OBJECTIVE

To evaluate the longitudinal association between ambient light exposure and the subsequent changes in obesity parameters.

DESIGN AND PARTICIPANTS

Data from 1110 elderly participants at baseline (mean age, 71.9 years) and data from 766 at follow-up (median, 21 months) were included in this prospective population-based study.

MEASURES

Time-dependent ambient light exposure based on objective measurements and changes in the waist-to-height ratio (WHtR) and body mass index (BMI) were measured.

RESULTS

Multivariable mixed-effect linear regression models showed a significant association between light exposure and the %WHtR gain; this was independent of potential confounders (eg, caloric intake, physical activity, and sleep/wake parameters). Nighttime or evening exposure to higher light intensity was significantly associated with subsequent %WHtR gain. Morning exposure to a longer time ≥500 lux or nighttime exposure to a longer time <3 lux was significantly associated with subsequent %WHtR loss. These association trends were nearly consistent when the BMI was used as an obesity parameter. Increased nighttime light exposure (mean ≥3 vs <3 lux) was estimated to correspond to a 10.2% WHtR gain and a 10.0% increase in BMI over 10 years.

CONCLUSIONS

Ambient light exposure, such as increased nighttime or evening light exposure and decreased morning light exposure, was independently associated with subsequent increases in obesity parameters. Further interventional studies are warranted to establish an optimal controlled lighting environment as a preventive option against obesity.

Environmental 24-hr Cycles Are Essential for Health

Circadian rhythms are deeply rooted in the biology of virtually all organisms. The pervasive use of artificial lighting in modern society disrupts circadian rhythms and can be detrimental to our health. To investigate the relationship between disrupting circadian rhythmicity and disease, we exposed mice to continuous light (LL) for 24 weeks and measured several major health parameters. Long-term neuronal recordings revealed that 24 weeks of LL reduced rhythmicity in the central circadian pacemaker of the suprachiasmatic nucleus (SCN) by 70%. Strikingly, LL exposure also reduced skeletal muscle function (forelimb grip strength, wire hanging duration, and grid hanging duration), caused trabecular bone deterioration, and induced a transient pro-inflammatory state. After the mice were returned to a standard light-dark cycle, the SCN neurons rapidly recovered their normal high-amplitude rhythm, and the aforementioned health parameters returned to normal. These findings strongly suggest that a disrupted circadian rhythm reversibly induces detrimental effects on multiple biological processes.

Outdoor artificial light at night, obesity, and sleep health: Cross-sectional analysis in the KoGES study

Obesity is a common disorder with many complications. Although chronodisruption plays a role in obesity, few epidemiological studies have investigated the association between artificial light at night (ALAN) and obesity. Since sleep health is related to both obesity and ALAN, we investigated the association between outdoor ALAN and obesity after adjusting for sleep health. We also investigated the association between outdoor ALAN and sleep health. This cross-sectional survey included 8526 adults, 39-70 years of age, who participated in the Korean Genome and Epidemiology Study. Outdoor ALAN data were obtained from satellite images provided by the US Defense Meteorological Satellite Program. We obtained individual data regarding outdoor ALAN; body mass index; depression; and sleep health including sleep duration, mid-sleep time, and insomnia; and other demographic data including age, sex, educational level, type of residential building, monthly household income, alcohol consumption, smoking status and consumption of caffeine or alcohol before sleep. A logistic regression model was used to investigate the association between outdoor ALAN and obesity. The prevalence of obesity differed significantly according to sex (women 47% versus men 39%, p < 0.001) and outdoor ALAN (high 55% versus low 40%, p < 0.001). Univariate logistic regression analysis revealed a significant association between high outdoor ALAN and obesity (odds ratio [OR] 1.24, 95% confidence interval [CI] 1.14-1.35, p < 0.001). Furthermore, multivariate logistic regression analyses showed that high outdoor ALAN was significantly associated with obesity after adjusting for age and sex (OR 1.25, 95% CI 1.14-1.37, p < 0.001) and even after controlling for various other confounding factors including age, sex, educational level, type of residential building, monthly household income, alcohol consumption, smoking, consumption of caffeine or alcohol before sleep, delayed sleep pattern, short sleep duration and habitual snoring (OR 1.20, 95% CI 1.06-1.36, p = 0.003). The findings of our study provide epidemiological evidence that outdoor ALAN is significantly related to obesity.

Does artificial light-at-night exposure contribute to the worldwide obesity pandemic?

BACKGROUND

Worldwide overweight and obesity rates are on the rise, with about 1 900 billion adults being defined as overweight and about 600 million adults being defined as obese by the World Health Organization (WHO). Increasing exposure to artificial light-at-night (ALAN) may influence body mass, by suppression of melatonin production and disruption of daily rhythms, resulting in physiological or behavioral changes in the human body, and may thus become a driving force behind worldwide overweight and obesity pandemic.

METHODS

We analyzed most recent satellite images of night time illumination, available from the US Defense Meteorological Satellite Program (DMSP), combining them with country-level data on female and male overweight and obesity prevalence rates, reported by the WHO. The study aims to identify and measure the strength of association between ALAN and country-wide overweight and obesity rates, controlling for per capita GDP, level of urbanization, birth rate, food consumption and regional differences.

RESULTS

ALAN emerged as a statistically significant and positive predictor of overweight and obesity (t>1.97; P<0.05), helping to explain, together with other factors, about 70% of the observed variation of overweight and obesity prevalence rates among females and males in more than 80 countries worldwide. Regional differences in the strength of association between ALAN and excessive body mass are also noted.

CONCLUSIONS

This study is the first population-level study that confirms the results of laboratory research and cohort studies in which ALAN was found to be a contributing factor to excessive body mass in humans.

Nocturnal light pollution and underexposure to daytime sunlight: Complementary mechanisms of circadian disruption and related diseases

Routine exposure to artificial light at night (ALAN) in work, home, and community settings is linked with increased risk of breast and prostate cancer (BC, PC) in normally sighted women and men, the hypothesized biological rhythm mechanisms being frequent nocturnal melatonin synthesis suppression, circadian time structure (CTS) desynchronization, and sleep/wake cycle disruption with sleep deprivation. ALAN-induced perturbation of the CTS melatonin synchronizer signal is communicated maternally at the very onset of life and after birth via breast or artificial formula feedings. Nighttime use of personal computers, mobile phones, electronic tablets, televisions, and the like--now epidemic in adolescents and adults and highly prevalent in pre-school and school-aged children--is a new source of ALAN. However, ALAN exposure occurs concomitantly with almost complete absence of daytime sunlight, whose blue-violet (446-484 nm λ) spectrum synchronizes the CTS and whose UV-B (290-315 nm λ) spectrum stimulates vitamin D synthesis. Under natural conditions and clear skies, day/night and annual cycles of UV-B irradiation drive corresponding periodicities in vitamin D synthesis and numerous bioprocesses regulated by active metabolites augment and strengthen the biological time structure. Vitamin D insufficiency and deficiency are widespread in children and adults in developed and developing countries as a consequence of inadequate sunlight exposure. Past epidemiologic studies have focused either on exposure to too little daytime UV-B or too much ALAN, respectively, on vitamin D deficiency/insufficiency or melatonin suppression in relation to risk of cancer and other, e.g., psychiatric, hypertensive, cardiac, and vascular, so-called, diseases of civilization. The observed elevated incidence of medical conditions the two are alleged to influence through many complementary bioprocesses of cells, tissues, and organs led us to examine effects of the totality of the artificial light environment in which humans reside today. Never have chronobiologic or epidemiologic investigations comprehensively researched the potentially deleterious consequences of the combination of suppressed vitamin D plus melatonin synthesis due to life in today's man-made artificial light environment, which in our opinion is long overdue.

[Sleep and sleep disorders in the elderly. Part 2: therapy]

Sleep disorders need to be treated if they affect the quality of life, lead to functional problems in daily life or unfavorably affect self-sufficiency. The large number of sleep disorders is reflected in the number of different and varied available therapeutic procedures. The basic therapeutic procedure for any sleep disorder is the use of sleep hygiene. Sleeplessness (insomnia) is most effectively treated through behavioral therapy, with stimulus control and sleep restriction as the most effective measures, whereas pharmacotherapy is considerably less effective and has side effects. Sleep-disordered breathing is also the most common cause of hypersomnia in the elderly and is most effectively treated by nocturnal positive pressure breathing.

Sleep cognitions associated with anxiety and depression in the elderly

PURPOSE

The objective of this study was to identify the maladaptive sleep-related cognitions most often maintained by the elderly, according to the presence or absence of anxiety and mood disorders. The presence of dysfunctional sleep-related beliefs and attitudes at bedtime in asymptomatic, depressive, and anxious seniors was thus compared. The second objective was to verify the relationships between various dysfunctional cognitions and mental disorders.

METHOD

The sample in this study consisted of 2,759 participants aged 65 years and over, with a mean age of 73.8 years. They were recruited through a method of random generation of telephone numbers according to a sampling strategy based on geographic location. After the goal of the study was explained to them, the participants agreed to have health professionals visit their home and to answer questions in a 1.5-hour-long structured interview (after signing a consent form).

RESULTS

Depressive and anxious seniors adopt dysfunctional sleep-related cognitions in higher proportions than asymptomatic older persons. Once we had controlled for the other factors, we were able to specifically link two sleep-related beliefs and all the sleep-related attitudes studied to the probability of being anxious or depressive.

CONCLUSION

The clarifications obtained will make it possible to improve detection, assessment, and intervention processes regarding anxiety or mood disorders, by pinpointing the most direct link between each of the dysfunctional cognitions and the two types of mental disorders, and not just the link to sleep problems.

Sleep and the endogenous melatonin rhythm of high arctic residents during the summer and winter

The seasonal extremes of photoperiod in high latitudes place particular strain on the human circadian system. Arctic residence has been associated with poor sleep in both summer and winter. The goal of the work reported here was to study the circadian rhythms of individuals living in the high Arctic by measuring sleep variables and the timing of melatonin production. Two research trials were conducted in the built environment of CFS Alert (82° 29' 58″ N). Participants wore motion logging devices (actigraphs), which measure ambient light as well as motion, for 1week to provide data on sleep quantity, quality and light exposure. On the penultimate day of each trial, the participants were maintained together in a gymnasium with lounge chairs and saliva was collected at regular intervals to measure melatonin and assess the dim light melatonin onset (DLMO), offset (MelOFF), 50% rise and fall times of the whole profile and total production. In general, sleep duration was found to be significantly different between the January and June data collections at CFS Alert, with participants in June sleeping 50min on average less each day compared to their January counterparts. In June sleep was mistimed in many subjects relative to circadian phase as evidenced by the melatonin rhythm. Exposure to bright evening light was the most likely causal factor and should be avoided in the Arctic summer. The Arctic summer represents a particularly challenging environment for obtaining sufficient sleep. This has implications for the cognitive performance of staff during work hours.

Association between light exposure at night and insomnia in the general elderly population: the HEIJO-KYO cohort

Chronic circadian misalignment between the internal and environmental rhythms, which is typically related to night-shift work and clock-gene variants, is associated with disruption of suprachiasmatic nucleus function and increased risk of insomnia. Under controlled laboratory conditions, light at night (LAN) suppresses melatonin secretion, delays the internal biological rhythm, and reduces sleepiness. Therefore, LAN exposure may cause circadian misalignment and insomnia, though it remains unclear in real-life situations whether LAN exposure is associated with insomnia. To evaluate an association between LAN exposure and sleep quality in home settings, we conducted a cross-sectional community-based study in 857 elderly individuals (mean age, 72.2 years). We evaluated bedroom light intensity using a light meter and subjectively and objectively measured sleep quality using the Pittsburgh Sleep Quality Index and an actigraph, respectively, along with urinary 6-sulfatoxymelatonin excretion. Compared with the lowest quartile group of LAN intensity, the highest quartile group revealed a significantly higher odds ratio (OR) for subjective insomnia in a multivariate model adjusted for age, gender, body mass index, daytime physical activity, urinary 6-sulfatoxymelatonin excretion, bedtime, rising time, and day length (adjusted OR, 1.61, 95% confidence interval, 1.05-2.45, p=0.029). In addition, higher OR for subjective insomnia was significantly associated with the increase in quartiles of LAN intensity (ptrend=0.043). Consistently, we observed significant association trends between the increase in quartiles of LAN intensity and poorer actigraphic sleep quality, including decreased sleep efficiency, prolonged sleep-onset latency, increased wake-after-sleep onset, shortened total sleep time, and delayed sleep-mid time in multivariate models adjusted for the covariates mentioned above (all ptrend<0.001). In conclusion, we demonstrated that LAN exposure in home settings is significantly associated with both subjectively and objectively measured sleep quality in a community-based elderly population.