Diminished melatonin secretion in the elderly caused by insufficient environmental illumination

Cognitive correlates of circadian rhythm and sleep-wake behaviour in chronic obstructive pulmonary disease patients

Chronic obstructive pulmonary disease (COPD) patients often experience reduced physical activity, sleep disturbances, and cognitive impairment. However, reports on measurement of rest-activity rhythm and sleep-wake behavior and their impact on cognitive functions in COPD patients are limited. This study aimed to objectively measure circadian rhythms (rest-activity and ambient illuminance) and sleep behaviors in clinically stable COPD patients and their relationship with cognitive functions. The study involved 65 male COPD patients and 50 age-matched controls, monitored over 3-7 days using actigraphy. Cognitive status was assessed using the Montreal Cognitive Assessment (MoCA) followed by short interbal time estimation via time production and reproduction with reaction time measurement using TimeProd software. Findings indicated significant disruptions in circadian rhythms in COPD patients, characterized by lower mesor, amplitude, and autocorrelation coefficients compared to controls. Patients also reported poorer sleep quality and higher sleep fragmentation, with 85.7% displaying cognitive impairment. Notably, longer time estimations, increased variability in task performance, and slower reaction times suggested cognitive deterioration. Positive correlations emerged between rhythm parameters (amplitude and circadian quotient) and cognitive performance metrics. This highlights the relevance of circadian and sleep disturbances in COPD, suggesting that addressing these rhythms could help mitigate cognitive decline, potentially through chronotherapeutic strategies.

The association between milk and dairy products intake and insomnia symptoms among Japanese adults in community-based cohort

Objective: To examine the association between habitual intake of milk and dairy products and insomnia. Design: Cross-sectional study by using cohort study data among 60,633 participants (22,721 men and 37,912 women) aged 20-74 years in eastern Japan. The data of milk and dairy products intake, sleep status and other lifestyle habits were collected by self-administered questionnaires. The question about milk and dairy products included whole milk, low-fat milk, cheese, yogurt, and lactic acid bacteria beverages, and were assessed by frequency (< 1 time/week, 1-2 times/week, 3-6 times/ week, and ≥ 1 time/day). Sleep status was scored with the Athens Insomnia Scale. Results: Logistic regression analysis showed that adjusted odds ratio (OR) and 95% confidence interval (95% CI) for insomnia were statistically significantly lower for whole milk intake > 1 time/day compared to < 1 time/week in all (OR: 0.91; 95% CI: 0.86-0.96; P = 0.001). The similar results were shown for women (OR: 0.90; 95% CI: 0.85-0.97; P = 0.002), not for men. In contrast, the adjusted odds for insomnia were high in the group that had frequencies of 3-6 times/week of lactic acid bacteria beverages compared to <1 time/week (OR: 1.20, 95% CI: 1.11-1.29; P < 0.001 in all; OR: 1.36; 95% CI: 1.19-1.55; P < 0.001 in men; OR: 1.13; 95% CI: 1.03-1.24; P = 0.009 in women). Conclusions: This cross-sectional study of Japanese populations showed a tendency for no insomniacs to consume whole milk more frequently.

Melatonin as a chronobiotic/cytoprotective agent in bone. Doses involved

Because the chronobiotic and cytoprotective molecule melatonin diminishes with age, its involvement in postmenopausal and senescence pathology has been considered since long. One relevant melatonin target site in aging individuals is bone where melatonin chronobiotic effects mediated by MT1 and MT2 receptors are demonstrable. Precursors of bone cells located in bone marrow are exposed to high quantities of melatonin and the possibility arises that melatonin acts a cytoprotective compound via an autacoid effect. Proteins that are incorporated into the bone matrix, like procollagen type I c-peptide, augment after melatonin exposure. Melatonin augments osteoprotegerin, an osteoblastic protein that inhibits the differentiation of osteoclasts. Osteoclasts are target cells for melatonin as they degrade bone partly by generating free radicals. Osteoclast activity and bone resorption are impaired via the free radical scavenger properties of melatonin. The administration of melatonin in chronobiotic doses (less than 10 mg daily) is commonly used in clinical studies on melatonin effect on bone. However, human equivalent doses allometrically derived from animal studies are in the 1-1.5 mg/kg/day range for a 75 kg human adult, a dose rarely used clinically. In view of the absence of toxicity of melatonin in phase 1 pharmacological studies with doses up to 100 mg in normal volunteers, further investigation is needed to determine whether high melatonin doses have higher therapeutic efficacy in preventing bone loss.

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.

Indoor Environmental Quality of Residential Elderly Care Facilities in Northeast China

The indoor environmental quality is based on the indoor environmental performance of buildings, such as air temperature, lighting, and acoustics. These parameters have a specific impact on users' health and experience. This study explores the relationship between the indoor environment of residential elderly care facilities in cold regions and the sensitivity of the elderly to these facilities with the aim of improving the elderly care environment. This study measured the acoustic, lighting, and thermal environment in four residential elderly care facilities in Northeast China in spring, summer, autumn, and winter through a participant survey. In the residential elderly care facilities surveyed in this study, brightness and illuminance show a nonlinear relationship with lighting evaluation. With an increase in brightness and illuminance, the satisfaction of the lighting environment in different seasons first increases and then decreases. The relative humidity of the different types of rooms varies greatly in spring and less in winter. The average air quality score of the bedroom is higher than that of the activity room. The correlation between odor assessment and overall indoor environmental quality is very poor. The results of the questionnaire survey indicate that the participants were satisfied with the facilities' overall indoor environmental quality. This quality is affected by physical, environmental, and demographic factors. This study provides a reference for the design of other residential elderly care facilities.

Melatonin profile in healthy, elderly subjects - A systematic literature review

Melatonin plays an important role in regulation and maintaining of the circadian rhythm. In the elderly population, an array of disturbances of circadian rhythm and sleep can be observed; however the current knowledge within the group of healthy, elderly is scarce. This systematic literature review of studies on the melatonin profile measured in the blood of healthy, elderly individuals included 519 studies, found in the primary search on PubMed. After reviewing the title and abstract, 47 studies were found eligible for full text review. The inclusion criteria were defined as follows: healthy, elderly individuals, with a mean or average age over 65 years and analysis done in blood or plasma. In addition to the primary search, three studies were directly identified by the reference lists of already included studies. A final total of 23 studies were included in the systematic literature review. In reviewing the literature, a clear circadian melatonin profile with a nocturnal peak at 3 am and lower daytime levels was observed in the healthy, elderly population. In elderly over 75 years of age, the nocturnal level of melatonin may be lower; however, the circadian rhythmicity is maintained. In the comparison of elderly, independently living individuals and individuals living in care facilities, the latter group had lower levels of nocturnal melatonin peak as well as higher daytime levels; however one can wonder if elderly in care facilities are healthy. The 23 included studies in the systematic literature review had varying primary objectives and generally the term "healthy" within this population group proves difficult to clearly define. As a result of this, an obvious interstudy variability existed, which is a limitation of this systematic literature review. However, the graphs depicted represent the best possible estimation of the melatonin profile in a healthy, elderly population. Future research in the melatonin profile within this population should focus on clearly defined healthy elderly to ensure a valid normal material in this age group.

Optimized office lighting advances melatonin phase and peripheral heat loss prior bedtime

Improving indoor lighting conditions at the workplace has the potential to support proper circadian entrainment of hormonal rhythms, sleep, and well-being. We tested the effects of optimized dynamic daylight and electric lighting on circadian phase of melatonin, cortisol and skin temperatures in office workers. We equipped one office room with an automated controller for blinds and electric lighting, optimized for dynamic lighting (= Test room), and a second room without any automated control (= Reference room). Young healthy participants (n = 34) spent five consecutive workdays in each room, where individual light exposure data, skin temperatures and saliva samples for melatonin and cortisol assessments were collected. Vertical illuminance in the Test room was 1177 ± 562 photopic lux (mean  ± SD) , which was 320 lux higher than in the Reference room (p < 0.01). Melanopic equivalent daylight (D65) illuminance was 931 ± 484 melanopic lux in the Test room and 730 ± 390 melanopic lux in the Reference room (p < 0.01). Individual light exposures resulted in a 50 min earlier time of half-maximum accumulated illuminance in the Test than the Reference room (p < 0.05). The melatonin secretion onset and peripheral heat loss in the evening occurred significantly earlier with respect to habitual sleeptime in the Test compared to the Reference room (p < 0.05). Our findings suggest that optimized dynamic workplace lighting has the potential to promote earlier melatonin onset and peripheral heat loss prior bedtime, which may be beneficial for persons with a delayed circadian timing system.

The role of melatonin in the molecular mechanisms underlying metaflammation and infections in obesity: A narrative review

Obesity is a chronic condition whose management is a critical challenge for physicians. The scientific community has increased its focus on the molecular mechanisms involved in obesity etiopathogenesis to better manage patients with obesity and its associated complications. The tight connection between adipose tissue and the immune system has been demonstrated to play a crucial role in inflammation, and melatonin is important for circadian rhythm regulation and metabolic homeostasis, in which it orchestrates several molecular mechanisms involved in obesity and associated inflammation. Melatonin also regulates innate and adaptive immunity; its antioxidant properties are linked to reduced predisposition to infection and weight gain in patients with obesity through the modulation of the immune response, which has a significant beneficial effect on inflammation and, consequently, on the metabolic state. Low melatonin levels have been linked to obesity, and melatonin supplementation can reduce body weight, improve metabolic profile, and ameliorate immune responses and pro-inflammatory stimuli. The role of melatonin in obesity is mainly related to improved oxidative stress signaling, modulation of adipokine secretion, and a switching from white-to-brown adipose tissue phenotype and activity. Moreover, the role of melatonin in obesity modulation by controlling circadian rhythm has recently emerged as a pivotal mechanism for lipid and glucose metabolism dysfunction in adipose, muscle, and liver tissues. Melatonin may also regulate the immune system by acting directly on thymus morphology and activity as well as by modulating oxidative stress and inflammatory states during infections. The tight association between melatonin and immune response regulation is coordinated by Toll-like receptors, which are rhythmically expressed during the day. Their expression may be strongly modulated by melatonin as their signaling is highly inhibited by melatonin. The current review summarizes studies of melatonin-induced mechanisms involved in infection regulation, particularly the modulation of obesity-associated inflammation and systemic complications.

Access to Daylight at Home Improves Circadian Alignment, Sleep, and Mental Health in Healthy Adults: A Crossover Study

As the primary environmental cue for the body’s master biological clock, light–dark patterns are key for circadian alignment and are ultimately fundamental to multiple dimensions of health including sleep and mental health. Although daylight provides the proper qualities of light for promoting circadian alignment, our modern indoor lifestyles offer fewer opportunities for adequate daylight exposure. This field study explores how increasing circadian-effective light in residences affects circadian phase, sleep, vitality, and mental health. In this crossover study, 20 residents spent one week in their apartments with electrochromic glass windows and another week with functionally standard windows with blinds. Calibrated light sensors revealed higher daytime circadian-effective light levels with the electrochromic glass windows, and participants exhibited consistent melatonin onset, a 22-min earlier sleep onset, and higher sleep regularity. In the blinds condition, participants exhibited a 15-min delay in dim light melatonin onset, a delay in subjective vitality throughout the day, and an overall lower positive affect. This study demonstrates the impact of daytime lighting on the physiological, behavioral, and subjective measures of circadian health in a real-world environment and stresses the importance of designing buildings that optimize daylight for human health and wellbeing.

The Effect of Bright Light Treatment on Rest-Activity Rhythms in People with Dementia: A 24-Week Cluster Randomized Controlled Trial

Bright light treatment is an effective way to influence circadian rhythms in healthy adults, but previous research with dementia patients has yielded mixed results. The present study presents a primary outcome of the DEM.LIGHT trial, a 24-week randomized controlled trial conducted at nursing homes in Bergen, Norway, investigating the effects of a bright light intervention. The intervention consisted of ceiling-mounted LED panels providing varying illuminance and correlated color temperature throughout the day, with a peak of 1000 lx, 6000 K between 10 a.m. and 3 p.m. Activity was recorded using actigraphs at baseline and after 8, 16, and 24 weeks. Non-parametric indicators and extended cosine models were used to investigate rest-activity rhythms, and outcomes were analyzed with multi-level regression models. Sixty-one patients with severe dementia (median MMSE = 4) were included. After 16 weeks, the acrophase was advanced from baseline in the intervention group compared to the control group (B = -1.02, 95%; CI = -2.00, -0.05). There was no significant difference between the groups on any other rest-activity measures. When comparing parametric and non-parametric indicators of rest-activity rhythms, 25 out of 35 comparisons were significantly correlated. The present results indicate that ambient bright light treatment did not improve rest-activity rhythms for people with dementia.

The Pathways Linking to Sleep Habits among Children and Adolescents: A Complete Survey at Setagaya-ku, Tokyo

It has been noted that Japanese children sleep the least in the world, and this has become a major social issue. This study examined the pathways linked to sleep habits (SH) among children and adolescents. A questionnaire-based survey was conducted in March 2019 on children and their parents at all 63 public elementary and 29 public junior high schools in Setagaya-ku, Tokyo. For the analysis, 22,385 pairs of children-parent responses (valid response rate: 68.8%) with no missing data were used. This survey collected data on SH, physical activity (PA), screen time (ST) for the child, and lifestyle and neighborhood social capital (NSC) for the parents. Moreover, the pathways linking 'NSC' → 'parental lifestyle' → 'child's PA/ST' →'child's SH' were examined through structural equation modeling. The results indicated that children's SH were affected by their PA and ST and influenced by the lifestyle of their parents and the NSC that surrounds them. Thus, we concluded that it is necessary to provide direct interventions and take additional measures with regard to parent lifestyle and their NSC to solve persistent sleep problems in children.

Bright daytime light enhances circadian amplitude in a diurnal mammal

Mammalian circadian rhythms are orchestrated by a master pacemaker in the hypothalamic suprachiasmatic nuclei (SCN), which receives information about the 24 h light-dark cycle from the retina. The accepted function of this light signal is to reset circadian phase in order to ensure appropriate synchronization with the celestial day. Here, we ask whether light also impacts another key property of the circadian oscillation, its amplitude. To this end, we measured circadian rhythms in behavioral activity, body temperature, and SCN electrophysiological activity in the diurnal murid rodent Rhabdomys pumilio following stable entrainment to 12:12 light-dark cycles at four different daytime intensities (ranging from 18 to 1,900 lx melanopic equivalent daylight illuminance). R. pumilio showed strongly diurnal activity and body temperature rhythms in all conditions, but measures of rhythm robustness were positively correlated with daytime irradiance under both entrainment and subsequent free run. Whole-cell and extracellular recordings of electrophysiological activity in ex vivo SCN revealed substantial differences in electrophysiological activity between dim and bright light conditions. At lower daytime irradiance, daytime peaks in SCN spontaneous firing rate and membrane depolarization were substantially depressed, leading to an overall marked reduction in the amplitude of circadian rhythms in spontaneous activity. Our data reveal a previously unappreciated impact of daytime light intensity on SCN physiology and the amplitude of circadian rhythms and highlight the potential importance of daytime light exposure for circadian health.

The Lighting Environment, Its Metrology, and Non-visual Responses

International standard CIE S 026:2018 provides lighting professionals and field researchers in chronobiology with a method to characterize light exposures with respect to non-visual photoreception and responses. This standard defines five spectral sensitivity functions that describe optical radiation for its ability to stimulate each of the five α-opic retinal photoreceptor classes that contribute to the non-visual effects of light in humans via intrinsically-photosensitive retinal ganglion cells (ipRGCs). The CIE also recently published an open-access α-opic toolbox that calculates all the quantities and ratios of the α-opic metrology in the photometric, radiometric and photon systems, based on either a measured (user-defined) spectrum or selected illuminants (A, D65, E, FL11, LED-B3) built into the toolbox. For a wide variety of ecologically-valid conditions, the melanopsin-based photoreception of ipRGCs has been shown to account for the spectral sensitivity of non-visual responses, from shifting the timing of nocturnal sleep and melatonin secretion to regulating steady-state pupil diameter. Recent findings continue to confirm that the photopigment melanopsin also plays a role in visual responses, and that melanopsin-based photoreception may have a significant influence on brightness perception and aspects of spatial vision. Although knowledge concerning the extent to which rods and cones interact with ipRGCs in driving non-visual effects is still growing, a CIE position statement recently used melanopic equivalent daylight (D65) illuminance in preliminary guidance on applying "proper light at the proper time" to manipulate non-visual responses. Further guidance on this approach is awaited from the participants of the 2nd International Workshop on Circadian and Neurophysiological Photometry (in Manchester, August 2019). The new α-opic metrology of CIE S 026 enables traceable measurements and a formal, quantitative specification of personal light exposures, photic interventions and lighting designs. Here, we apply this metrology to everyday light sources including a natural daylight time series, a range of LED lighting products and, using the toobox, to a smartphone display screen. This collection of examples suggests ways in which variations in the melanopic content of light over the day can be adopted in strategies that use light to support human health and well-being.

Time spent outdoors and sleep normality: A preliminary investigation

INTRODUCTION

Sleep deficiency is associated with health risks, and time outdoors is related to health benefits. This study assessed time outdoors and its association with sleep normality.

METHODS

As part of a health study in Louisville, Kentucky, 735 participants completed questionnaires on their health status, behaviors, neighborhoods, and demographics in 2018-2019. The measures included information on sleep, time outdoors, and mental and physical health. Participant characteristics were assessed by dichotomized sleep normality (N=728), and logistic regression (N=709) examined potential associations between time outdoors and sleep.

RESULTS

As time spent outdoors increased from ≤4 hours to >4 - ≤8 hours (OR=1.04; 95% CI: 0.65-1.64) and >8 - ≤12 hours (OR=1.17; 95% CI: 0.63-2.17), odds of normal sleep increased; however, those who spent >12 - ≤16 hours (OR=0.63; 95% CI: 0.31-1.27) or >16 hours (OR=0.83; 95% CI: 0.45-1.53) outdoors had a lower likelihood of normal sleep. No associations between time outdoors and sleep were significant. There was a significant trend of less bodily pain associated with normal sleep (p<0.001) and in the association of depression and sleep, where odds of normal sleep decreased as depression severity increased (p<0.001).

CONCLUSIONS

Consistent with extant literature, findings indicate associations between less pain and increased odds of normal sleep and between higher severity of depression and lower odds of normal sleep. Findings for an overall association between time outdoors and sleep normality were not significant. Future work should seek to better explicate the predictor variables to assess how greenness and activity type shape associations with sleep.

Age-related neuroendocrine and alerting responses to light

Aging is associated with sleep and circadian alterations, which can negatively affect quality of life and longevity. Importantly, the age-related reduction in light sensitivity, particularly in the short-wavelength range, may underlie sleep and circadian alterations in older people. While evidence suggests that non-image-forming (NIF) light responses may diminish in older individuals, most laboratory studies have low sample sizes, use non-ecological light settings (e.g., monochromatic light), and typically focus on melatonin suppression by light. Here, we investigated whether NIF light effects on endogenous melatonin levels and sleep frontal slow-wave activity (primary outcomes), and subjective sleepiness and sustained attention (secondary outcomes) attenuate with aging. We conducted a stringently controlled within-subject study with 3 laboratory protocols separated by ~ 1 week in 31 young (18-30 years; 15 women) and 16 older individuals (55-80 years; eight women). Each protocol included 2 h of evening exposure to commercially available blue-enriched polychromatic light (6500 K) or non-blue-enriched light (3000 K or 2500 K) at low levels (~ 40 lx, habitual in evening indoor settings). Aging significantly affected the influence of light on endogenous melatonin levels, subjective sleepiness, sustained attention, and frontal slow-wave activity (interaction: P < 0.001, P = 0.004, P = 0.007, P = 0.001, respectively). In young individuals, light exposure at 6500 K significantly attenuated the increase in endogenous melatonin levels, improved subjective sleepiness and sustained attention performance, and decreased frontal slow-wave activity in the beginning of sleep. Conversely, older individuals did not exhibit signficant differential light sensitivity effects. Our findings provide evidence for an association of aging and reduced light sensitivity, with ramifications to sleep, cognition, and circadian health in older people.

The Sleep Side of Aging and Alzheimer's Disease

As we age, sleep patterns undergo significant modifications in micro and macrostructure, worsening cognition and quality of life. These are associated with remarkable brain changes, like deterioration in synaptic plasticity, gray and white matter, and significant modifications in hormone levels. Sleep alterations are also a core component of mild cognitive impairment (MCI) and Alzheimer's Disease (AD). AD night time is characterized by a gradual decrease in slow-wave activity and a substantial reduction of REM sleep. Sleep abnormalities can accelerate AD pathophysiology, promoting the accumulation of amyloid-β (Aβ) and phosphorylated tau. Thus, interventions that target sleep disturbances in elderly people and MCI patients have been suggested as a possible strategy to prevent or decelerate conversion to dementia. Although cognitive-behavioral therapy and pharmacological medications are still first-line treatments, despite being scarcely effective, new interventions have been proposed, such as sensory stimulation and Noninvasive Brain Stimulation (NiBS). The present review outlines the current state of the art of the relationship between sleep modifications in healthy aging and the neurobiological mechanisms underlying age-related changes. Furthermore, we provide a critical analysis showing how sleep abnormalities influence the prognosis of AD pathology by intensifying Aβ and tau protein accumulation. We discuss potential therapeutic strategies to target sleep disruptions and conclude that there is an urgent need for testing new therapeutic sleep interventions.

Light in the Senior Home: Effects of Dynamic and Individual Light Exposure on Sleep, Cognition, and Well-Being

Disrupted sleep is common among nursing home patients and is associated with cognitive decline and reduced well-being. Sleep disruptions may in part be a result of insufficient daytime light exposure. This pilot study examined the effects of dynamic “circadian” lighting and individual light exposure on sleep, cognitive performance, and well-being in a sample of 14 senior home residents. The study was conducted as a within-subject study design over five weeks of circadian lighting and five weeks of conventional lighting, in a counterbalanced order. Participants wore wrist accelerometers to track rest–activity and light profiles and completed cognitive batteries (National Institute of Health (NIH) toolbox) and questionnaires (depression, fatigue, sleep quality, lighting appraisal) in each condition. We found no significant differences in outcome variables between the two lighting conditions. Individual differences in overall (indoors and outdoors) light exposure levels varied greatly between participants but did not differ between lighting conditions, except at night (22:00–6:00), with maximum light exposure being greater in the conventional lighting condition. Pooled data from both conditions showed that participants with higher overall morning light exposure (6:00–12:00) had less fragmented and more stable rest–activity rhythms with higher relative amplitude. Rest–activity rhythm fragmentation and long sleep duration both uniquely predicted lower cognitive performance.

Sleep, Noninvasive Brain Stimulation, and the Aging Brain: Challenges and Opportunities

As we age, sleep patterns undergo severe modifications of their micro and macrostructure, with an overall lighter and more fragmented sleep structure. In general, interventions targeting sleep represent an excellent opportunity not only to maintain life quality in the healthy aging population, but also to enhance cognitive performance and, when pathology arises, to potentially prevent/slow down conversion from e.g. Mild Cognitive Impairment (MCI) to Alzheimer's Disease (AD). Sleep abnormalities are, in fact, one of the earliest recognizable biomarkers of dementia, being also partially responsible for a cascade of cortical events that worsen dementia pathophysiology, including impaired clearance systems leading to build-up of extracellular amyloid-β (Aβ) peptide and intracellular hyperphosphorylated tau proteins. In this context, Noninvasive Brain Stimulation (NiBS) techniques, such as transcranial electrical stimulation (tES) and transcranial magnetic stimulation (TMS), may help investigate the neural substrates of sleep, identify sleep-related pathology biomarkers, and ultimately help patients and healthy elderly individuals to restore sleep quality and cognitive performance. However, brain stimulation applications during sleep have so far not been fully investigated in healthy elderly cohorts, nor tested in AD patients or other related dementias. The manuscript discusses the role of sleep in normal and pathological aging, reviewing available evidence of NiBS applications during both wakefulness and sleep in healthy elderly individuals as well as in MCI/AD patients. Rationale and details for potential future brain stimulation studies targeting sleep alterations in the aging brain are discussed, including enhancement of cognitive performance, overall quality of life as well as protein clearance.

Aging-related changes on social synchronization of circadian activity rhythm in a diurnal primate (Callithrix jacchus)

The input of environmental time cues and expression of circadian activity rhythms may change with aging. Among nonphotic zeitgebers, social cues from conspecific vocalizations may contribute to the stability and survival of individuals of social species, such as nonhuman primates. We evaluated aging-related changes on social synchronization of the circadian activity rhythm (CAR) in a social diurnal primate, the common marmoset. The activity of 18 male marmosets was recorded by actiwatches in two conditions. (1) Experimental - 4 young adult (5 ± 2 yrs of age) and 4 older (10 ± 2 yrs of age) animals maintained under LD 12/12 h and LL in a room with full insulation for light but only partial insulation for sound from vocalizations of conspecifics maintained outdoors in the colony; and (2) Control - 10 young adult animals maintained outdoors in the colony (5 animals as a control per age group). In LL, the CAR of young adults showed more stable synchronization with controls. Among the aged marmosets, two free-ran with τ > 24 h, whereas the other two showed relative coordination during the first 30 days in LL, but free-ran thereafter. These differences were reflected in the "social" phase angles (ψ_on and ψ_off ) between rhythms of experimental and control animal groups. Moreover, the activity patterns of aged animals showed lower social synchrony with controls compared to young adults, with the time lags of the time series between each experimental group and control group being negative in aged and positive in young adult animals (t-test, p < 0.05). The index of stability of the CAR showed no differences according to age, while the intradaily variability of the CAR was higher in the aged animals during LD-resynchronization, who took additional days to resynchronize. Thus, the social modulation on CAR may vary with age in marmosets. In the aged group, there was a lower effect of social synchronization, which may be associated with aging-related changes in the synchronization and generation of the CAR as well as in system outputs.

An Actigraphy-Based Validation Study of the Sleep Disorder Inventory in the Nursing Home

Background: Disrupted sleep is common among nursing home patients with dementia and is associated with increased agitation, depression, and cognitive impairment. Detecting and treating sleep problems in this population are therefore of great importance, albeit challenging. Systematic observation and objective recordings of sleep are time-consuming and resource intensive and self-report is often unreliable. Commonly used proxy-rated scales contain few sleep items, which affects the reliability of the raters' reports. The present study aimed to adapt the proxy-rated Sleep Disorder Inventory (SDI) to a nursing home context and validate it against actigraphy. Methods: Cross-sectional study of 69 nursing home patients, 68% women, mean age 83.5 (SD 7.1). Sleep was assessed with the SDI, completed by nursing home staff, and with actigraphy (Actiwatch II, Philips Respironics). The SDI evaluates the frequency, severity, and distress of seven sleep-related behaviors. Internal consistency of the SDI was evaluated by Cronbach's alpha. Spearman correlations were used to evaluate the convergent validity between actigraphy and the SDI. Test performance was assessed by calculating the sensitivity, specificity, and predictive values, and by ROC curve analyses. The Youden's Index was used to determine the most appropriate cut-off against objectively measured sleep disturbance defined as <6 h nocturnal total sleep time (TST) during 8 h nocturnal bed rest (corresponding to SE <75%). Results: The SDI had high internal consistency and convergent validity. Three SDI summary scores correlated moderately and significantly with actigraphically measured TST and wake-after-sleep-onset. A cut-off score of five or more on the SDI summed product score (sum of the products of the frequency and severity of each item) yielded the best sensitivity, specificity, predictive values, and Youden's Index. Conclusion: We suggest a clinical cut-off for the presence of disturbed sleep in institutionalized dementia patients to be a SDI summed product score of five or more. The results suggest that the SDI can be clinically useful for the identification of disrupted sleep when administered by daytime staff in a nursing home context. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03357328.

Assessing Chronotypes by Ambulatory Circadian Monitoring

In order to develop objective indexes for chronotype identification by means of direct measurement of circadian rhythms, 159 undergraduate students were recruited as volunteers and instructed to wear ambulatory circadian monitoring (ACM) sensors that continuously gathered information on the individual's environmental light and temperature exposure, wrist temperature, body position, activity, and the integrated TAP (temperature, activity, and position) variable for 7 consecutive days under regular free-living conditions. Among all the proposed indexes, the night phase marker (NPM) of the TAP variable was the best suited to discriminate among chronotypes, due to its relationship with the Munich ChronoType Questionnaire (β = 0.531; p < 0.001). The NPM of TAP allowed subjects to be classified as early- (E-type, 20%), neither- (N-type, 60%), and late-types (L-type, 20%), each of which had its own characteristics. In terms of light exposure, while all subjects had short exposure times to bright light (>100 lux), with a daily average of 93.84 ± 5.72 min, the earlier chronotypes were exposed to brighter days and darker nights compared to the later chronotypes. Furthermore, the earlier chronotypes were associated with higher stability and day-night contrast, along with an earlier phase, which could be the cause or consequence of the light exposure habits. Overall, these data support the use of ACM for chronotype identification and for evaluation under free living conditions, using objective markers.

Early evening light mitigates sleep compromising physiological and alerting responses to subsequent late evening light

The widespread use of electric light and electronic devices has resulted in an excessive exposure to light during the late-evening and at night. This late light exposure acutely suppresses melatonin and sleepiness and delays the circadian clock. Here we investigate whether the acute effects of late-evening light exposure on our physiology and sleepiness are reduced when this light exposure is preceded by early evening bright light. Twelve healthy young females were included in a randomised crossover study. All participants underwent three evening (18:30-00:30) sessions during which melatonin, subjective sleepiness, body temperature and skin blood flow were measured under different light conditions: (A) dim light, (B) dim light with a late-evening (22:30-23:30) light exposure of 750 lx, 4000 K, and (C) the same late-evening light exposure, but now preceded by early-evening bright light exposure (18.30-21.00; 1200 lx, 4000 K). Late-evening light exposure reduced melatonin levels and subjective sleepiness and resulted in larger skin temperature gradients as compared to dim. Interestingly, these effects were reduced when the late-evening light was preceded by an early evening 2.5-hour bright light exposure. Thus daytime and early-evening exposure to bright light can mitigate some of the sleep-disruptive consequences of light exposure in the later evening.

A defined human aging phenome

Aging is among the most complex phenotypes that occur in humans. Identifying the interplay between different age-associated features is undoubtedly critical to our understanding of aging and thus age-associated diseases. Nevertheless, what constitutes human aging is not well characterized. Towards this end, we mined millions of PubMed abstracts for age-associated terms, enabling us to generate a detailed description of the human aging phenotype. We discovered age-associated features in clusters that can be broadly associated with previously defined hallmarks of aging, consequently identifying areas where interventions could be pursued. Importantly, we validated the newly discovered features by manually verifying the prevalence of these features in combined cohorts describing 76 million individuals, allowing us to stratify features in aging that appear to be the most prominent. In conclusion, we propose a comprehensive landscape of human aging: the human aging phenome.

Chronotype-Dependent Changes in Sleep Habits Associated with Dim Light Melatonin Onset in the Antarctic Summer

Dim light melatonin onset (DLMO) is the most reliable measure of human central circadian timing. Its modulation by light exposure and chronotype has been scarcely approached. We evaluated the impact of light changes on the interaction between melatonin, sleep, and chronotype in university students (n = 12) between the Antarctic summer (10 days) and the autumn equinox in Montevideo, Uruguay (10 days). Circadian preferences were tested by validated questionnaires. A Morningness–Eveningness Questionnaire average value (47 ± 8.01) was used to separate late and early participants. Daylight exposure (measured by actimetry) was significantly higher in Antarctica versus Montevideo in both sensitive time windows (the morning phase-advancing and the evening phase-delaying). Melatonin was measured in hourly saliva samples (18–24 h) collected in dim light conditions (<30 lx) during the last night of each study period. Early and late participants were exposed to similar amounts of light in both sites and time windows, but only early participants were significantly more exposed during the late evening in Antarctica. Late participants advanced their DLMO with no changes in sleep onset time in Antarctica, while early participants delayed their DLMO and sleep onset time. This different susceptibility to respond to light may be explained by a subtle difference in evening light exposure between chronotypes.

The Effects of Naturalistic Light on Diurnal Plasma Melatonin and Serum Cortisol Levels in Stroke Patients during Admission for Rehabilitation: A Randomized Controlled Trial

Background: Stroke patients admitted for rehabilitation often lack sufficient daytime blue light exposure due to the absence of natural light and are often exposed to light at unnatural time points. We hypothesized that artificial light imitating daylight, termed naturalistic light, would stabilize the circadian rhythm of plasma melatonin and serum cortisol levels among long-term hospitalized stroke patients. Methods: A quasi-randomized controlled trial. Stroke patients in need of rehabilitation were randomized between May 1, 2014, and June 1, 2015 to either a rehabilitation unit equipped entirely with always on naturalistic lighting (IU), or to a rehabilitation unit with standard indoor lighting (CU). At both inclusion and discharge after a hospital stay of at least 2 weeks, plasma melatonin and serum cortisol levels were measured every 4 hours over a 24-hour period. Circadian rhythm was estimated using cosinor analysis, and variance between time-points. Results: A total of 43 were able to participate in the blood collection. Normal diurnal rhythm of melatonin was disrupted at both inclusion and discharge. In the IU group, melatonin plasma levels were increased at discharge compared to inclusion (n = 23; median diff, 2.9; IQR: -1.0 to 9.9, p = 0.030) and rhythmicity evolved (n = 23; p = 0.007). In the CU group, melatonin plasma levels were similar between discharge and inclusion and no rhythmicity evolved. Overall, both patient groups showed normal cortisol diurnal rhythms at both inclusion and discharge. Conclusions: This study is the first to demonstrate elevated melatonin plasma levels and evolved rhythmicity due to stimulation with naturalistic light.

Circadian regulation of glucose, lipid, and energy metabolism in humans

The circadian system orchestrates metabolism in daily 24-hour cycles. Such rhythms organize metabolism by temporally separating opposing metabolic processes and by anticipating recurring feeding-fasting cycles to increase metabolic efficiency. Although animal studies demonstrate that the circadian system plays a pervasive role in regulating metabolism, it is unclear how, and to what degree, circadian research in rodents translates into humans. Here, we review evidence that the circadian system regulates glucose, lipid, and energy metabolism in humans. Using a range of experimental protocols, studies in humans report circadian rhythms in glucose, insulin, glucose tolerance, lipid levels, energy expenditure, and appetite. Several of these rhythms peak in the biological morning or around noon, implicating earlier in the daytime is optimal for food intake. Importantly, disruptions in these rhythms impair metabolism and influence the pathogenesis of metabolic diseases. We therefore also review evidence that circadian misalignment induced by mistimed light exposure, sleep, or food intake adversely affects metabolic health in humans. These interconnections among the circadian system, metabolism, and behavior underscore the importance of chronobiology for preventing and treating type 2 diabetes, obesity, and hyperlipidemia.

Light color importance for circadian entrainment in a diurnal (Octodon degus) and a nocturnal (Rattus norvegicus) rodent

The central circadian pacemaker (Suprachiasmatic Nuclei, SCN) maintains the phase relationship with the external world thanks to the light/dark cycle. Light intensity, spectra, and timing are important for SCN synchronisation. Exposure to blue-light at night leads to circadian misalignment that could be avoided by using less circadian-disruptive wavelengths. This study tests the capacity of a diurnal Octodon degus and nocturnal Rattus norvegicus to synchronise to different nocturnal lights. Animals were subjected to combined red-green-blue lights (RGB) during the day and to: darkness; red light (R); combined red-green LED (RG) lights; and combined red-green-violet LED (RGV) lights during the night. Activity rhythms free-ran in rats under a RGB:RG cycle and became arrhythmic under RGB:RGV. Degus remained synchronised, despite the fact that day and night-time lighting systems differed only in spectra, but not in intensity. For degus SCN c-Fos activation by light was stronger with RGB-light than with RGV. This could be relevant for developing lighting that reduces the disruptive effects of nocturnal light in humans, without compromising chromaticity.

Differential impact in young and older individuals of blue-enriched white light on circadian physiology and alertness during sustained wakefulness

We tested the effect of different lights as a countermeasure against sleep-loss decrements in alertness, melatonin and cortisol profile, skin temperature and wrist motor activity in healthy young and older volunteers under extendend wakefulness. 26 young [mean (SE): 25.0 (0.6) y)] and 12 older participants [(mean (SE): 63.6 (1.3) y)] underwent 40-h of sustained wakefulness during 3 balanced crossover segments, once under dim light (DL: 8 lx), and once under either white light (WL: 250 lx, 2,800 K) or blue-enriched white light (BL: 250 lx, 9,000 K) exposure. Subjective sleepiness, melatonin and cortisol were assessed hourly. Skin temperature and wrist motor activity were continuously recorded. WL and BL induced an alerting response in both the older (p = 0.005) and the young participants (p = 0.021). The evening rise in melatonin was attentuated under both WL and BL only in the young. Cortisol levels were increased and activity levels decreased in the older compared to the young only under BL (p = 0.0003). Compared to the young, both proximal and distal skin temperatures were lower in older participants under all lighting conditions. Thus the color temperature of normal intensity lighting may have differential effects on circadian physiology in young and older individuals.

The suprachiasmatic nucleus: age-related decline in biological rhythms

Aging is associated with changes in sleep duration and quality, as well as increased rates of pathologic/disordered sleep. While several factors contribute to these changes, emerging research suggests that age-related changes in the mammalian central circadian clock within the suprachiasmatic nucleus (SCN) may be a key factor. Prior work from our group suggests that circadian output from the SCN declines because of aging. Furthermore, we have previously observed age-related infertility in female mice, caused by a mismatch between environmental light-dark cycles and the intrinsic, internal biological clocks. In this review, we address regulatory mechanisms underlying circadian rhythms in mammals and summarize recent literature describing the effects of aging on the circadian system.

Pineal Gland Volume Assessed by MRI and Its Correlation with 6-Sulfatoxymelatonin Levels among Older Men

The pineal gland produces the hormone melatonin, and its volume may influence melatonin levels. We describe an innovative method for estimating pineal volume in humans and present the association of pineal parenchyma volume with levels of the primary melatonin metabolite, 6-sulfatoxymelatonin. We selected a random sample of 122 older Icelandic men nested within the AGES-Reykjavik cohort and measured their total pineal volume, their parenchyma volume, and the extent of calcification and cysts. For volume estimations we used manual segmentation of magnetic resonance images in the axial plane with simultaneous side-by-side view of the sagittal and coronal plane. We used multivariable adjusted linear regression models to estimate the association of pineal parenchyma volume and baseline characteristics, including 6-sulfatoxymelatonin levels. We used logistic regression to test for differences in first morning urinary 6-sulfatoxymelatonin levels among men with or without cystic or calcified glands. The pineal glands varied in volume, shape, and composition. Cysts were present in 59% of the glands and calcifications in 21%. The mean total pineal volume measured 207 mm(3) (range 65-536 mm(3)) and parenchyma volume 178 mm(3) (range 65-503 mm(3)). In multivariable-adjusted models, pineal parenchyma volume was positively correlated with 6-sulfatoxymelatonin levels (β = 0.52, p < 0.001). Levels of 6-sulfatoxymelatonin did not differ significantly by presence of cysts or calcification. By using an innovative method for pineal assessment, we found pineal parenchyma volume to be positively correlated with 6-sulfatoxymelatonin levels, in line with other recent studies.

Annual variation in daily light exposure and circadian change of melatonin and cortisol concentrations at a northern latitude with large seasonal differences in photoperiod length

Background

Seasonal variations in physiology and behavior have frequently been reported. Light is the major zeitgeber for synchronizing internal circadian rhythms with the external solar day. Non-image forming effects of light radiation, for example, phase resetting of the circadian rhythms, melatonin suppression, and acute alerting effects, depend on several characteristics of the light exposure including intensity, timing and duration, spectral composition and previous light exposure, or light history. The aim of the present study was to report on the natural pattern of diurnal and seasonal light exposure and to examine seasonal variations in the circadian change of melatonin and cortisol concentrations for a group of Swedish office workers.

Methods

Fifteen subjects participated in a field study that was carried out in the south of Sweden. Ambulatory equipment was used for monthly measurements of the daily exposure to light radiation across the year. The measurements included illuminance and irradiance. The subjects collected saliva samples every 4 h during 1 day of the monthly measuring period.

Results

The results showed that there were large seasonal differences in daily amount of light exposure across the year. Seasonal differences were observed during the time periods 04:00–08:00, 08:00–12:00, 12:00–16:00, 16:00–20:00, and 20:00–24:00. Moreover, there were seasonal differences regarding the exposure pattern. The subjects were to a larger extent exposed to light in the afternoon/evening in the summer. During the winter, spring, and autumn, the subjects received much of the daily light exposure in the morning and early afternoon. Regarding melatonin, a seasonal variation was observed with a larger peak level during the winter and higher levels in the morning at 07:00.

Conclusions

This study adds to the results from other naturalistic studies by reporting on the diurnal and seasonal light exposure patterns for a group living at a northern latitude of 56° N, with large annual variations in photoperiod length. It seems to be seasonal variation in the lighting conditions, both concerning intensities as well as regarding the pattern of the light exposure to which people living at high latitudes are exposed which may result in seasonal variation in the circadian profile of melatonin.

Good daily habits during the early stages of life determine success throughout life

This paper assesses hypothesis that sufficient sleep duration and proper circadian rhythms during the early stages of life are indispensable to a successful life. Successful life was defined according to the famous cohort studies of Mischel's and Dunedin. To assess the hypothesis, neuronal elements presumably affecting early daily habits and successful life are reviewed. The effect of sufficient sleep duration and proper circadian rhythms during early stages of life on the development of the prefrontal cortex has been found to be the key issue to verify the hypothesis. Socioeconomic status is found to be another issue to be studied.

Associated depression in pseudophakic patients with intraocular lens with and without chromophore

BACKGROUND

With aging, the crystalline lens turns yellowish, which increases the absorption of wavelengths in the blue electromagnetic spectrum, reducing their photoreception in the retina. Since these wavelengths are the main stimulus in the regulation of the circadian rhythm, progressive reduction in their transmission is associated with chronic sleep disturbances and depression in elderly patients. Cataract extraction improves circadian photoreception at any age. However, lenses that block blue waves have 27% to 38% less melatonin suppression than lenses that block only ultraviolet (UV) rays.

PURPOSE

To assess the depression symptoms in subjects who have had bilateral phacoemul-sification and intraocular lens (IOL) implants, one group with yellow chromophore IOLs and the other group with transparent IOLs were compared.

SETTING

Association to Prevent Blindness in Mexico (APEC), Hospital "Dr Luis Sánchez Bulnes".

DESIGN

This was an observational, cross-sectional, and single-center study.

MATERIALS AND METHODS

Twenty-six subjects between 60 and 80 years of age, with a history of bilateral phacoemulsification and placement of the same type of IOL in both eyes from 4 to 12 months prior to the study, who attended the follow-up visits and agreed to participate in this study, and provided signed informed consent were included in the study. They were asked to answer the short version of the 15-item Geriatric Depression Scale.

RESULTS

The average age of the study participants was 72.5±5.94 years. The group without chromophore included 46.1% (n=12) of the patients and the group with chromophore included 53.9% (n=14) of the patients (P=0.088).

CONCLUSION

In the group of patients with IOLs that block the passage of blue light, the depression rate was 21.4%, a rate similar to that observed in the elderly population, whereas no patients in the group with transparent IOLs had depression.

Age-Related Changes in the Circadian System Unmasked by Constant Conditions

Circadian timing systems, like most physiological processes, cannot escape the effects of aging. With age, humans experience decreased duration and quality of sleep. Aged mice exhibit decreased amplitude and increased fragmentation of the activity rhythm, and lengthened circadian free-running period in both light-dark (LD) and constant dark (DD) conditions. Several studies have shown that aging impacts neural activity rhythms in the central circadian clock in the suprachiasmatic nucleus (SCN). However, evidence for age-related disruption of circadian oscillations of clock genes in the SCN has been equivocal. We hypothesized that daily exposure to LD cycles masks the full impact of aging on molecular rhythms in the SCN. We performed ex vivo bioluminescent imaging of cultured SCN slices of young and aged PER2::luciferase knock-in (PER2::LUC) mice housed under LD or prolonged DD conditions. Under LD conditions, the amplitude of PER2::LUC rhythms differed only slightly between SCN explants from young and aged animals; under DD conditions, the PER2::LUC rhythms of aged animals showed markedly lower amplitudes and longer circadian periods than those of young animals. Recordings of PER2::LUC rhythms in individual SCN cells using an electron multiplying charge-coupled device camera revealed that aged SCN cells showed longer circadian periods and that the rhythms of individual cells rapidly became desynchronized. These data suggest that aging degrades the SCN circadian ensemble, but that recurrent LD cycles mask these effects. We propose that these changes reflect a decline in pacemaker robustness that could increase vulnerability to environmental challenges, and partly explain age-related sleep and circadian disturbances.

Sleep insufficiency and the natural environment: Results from the US Behavioral Risk Factor Surveillance System survey

BACKGROUND

Exposure to the natural environment may improve health behaviors and mental health outcomes such as increased levels of physical activity and lower levels of depression associated with sleep quality. Little is known about the relationship between insufficient sleep and the natural environment.

PURPOSE

To determine whether exposure to attributes of the natural environment (e.g., greenspace) attenuates the likelihood of reporting insufficient sleep among US adults.

METHODS

Multiple logistic regression models were used to explore the association between self-reported days of insufficient sleep (in the past 30days) and access to the natural environment in a multi-ethnic, nationally representative sample (n=255,171) of US adults ≥18years of age enrolled in the 2010 Behavioral Risk Factor Surveillance System.

RESULTS

Using 1-to-6days of insufficient sleep as the referent group for all analyses, lower odds of exposure to natural amenities were observed for individuals reporting 21-to-29days (OR=0.843, 95% confidence interval (CI)=0.747, 0.951) of insufficient sleep. In stratified analyses, statistically significant lower odds of exposure to natural amenities were found among men reporting 7-to-13-days (OR=0.911, 95% CI=0.857, 0.968), 21-to-29-days (OR=0.838, 95% CI=0.759, 0.924), and 30-days (OR=0.860, 95% CI=0.784, 0.943) of insufficient sleep. Greenspace access was also protective against insufficient sleep for men and individuals aged 65+.

CONCLUSIONS

In a representative sample of US adults, access to the natural environment attenuated the likelihood of reporting insufficient sleep, particularly among men. Additional studies are needed to examine the impact of natural environment exposure on sleep insufficiency across various socio-demographic groups.

Effects of day-time exposure to different light intensities on light-induced melatonin suppression at night

Background

Bright nocturnal light has been known to suppress melatonin secretion. However, bright light exposure during the day-time might reduce light-induced melatonin suppression (LIMS) at night. The effective proportion of day-time light to night-time light is unclear; however, only a few studies on accurately controlling both day- and night-time conditions have been conducted. This study aims to evaluate the effect of different day-time light intensities on LIMS.

Methods

Twelve male subjects between the ages of 19 and 23 years (mean ± S.D., 20.8 ± 1.1) gave informed consent to participate in this study. They were exposed to various light conditions (<10, 100, 300, 900 and 2700 lx) between the hours of 09:00 and 12:00 (day-time light conditions). They were then exposed to bright light (300 lx) again between 01:00 and 02:30 (night-time light exposure). They provided saliva samples before (00:55) and after night-time light exposure (02:30).

Results

A one-tailed paired t test yielded significant decrements of melatonin concentration after night-time light exposure under day-time dim, 100- and 300-lx light conditions. No significant differences exist in melatonin concentration between pre- and post-night-time light exposure under day-time 900- and 2700-lx light conditions.

Conclusions

Present findings suggest the amount of light exposure needed to prevent LIMS caused by ordinary nocturnal light in individuals who have a general life rhythm (sleep/wake schedule). These findings may be useful in implementing artificial light environments for humans in, for example, hospitals and underground shopping malls.

Comparisons of Objective Sleep Quality Between Elderly Individuals With and Without Cataract Surgery: A Cross-Sectional Study of the HEIJO-KYO Cohort

Background

Cataract surgery (CS) drastically increases the capacity for light reception to the retina. Several previous studies have suggested the beneficial effect of CS on subjectively measured sleep quality; however, the association between CS and objectively measured sleep quality remains uncertain.

Methods

To evaluate the association between CS and objectively measured sleep quality in home settings, we conducted a cross-sectional study in 1037 elderly individuals (mean age, 71.9 years). We evaluated actigraphically measured sleep quality, urinary 6-sulfatoxymelatonin excretion, and ambulatory light levels, in addition to CS status.

Results

The CS group (n = 174) showed significantly higher sleep efficiency and shorter wake after sleep onset than the no CS group (n = 863), even after adjustment for age, gender, body mass index, current smoking status, alcohol consumption, hypertension, diabetes, sleep medication, bedtime, rising time, daytime physical activity, daytime and nighttime light exposure, and urinary 6-sulfatoxymelatonin excretion (sleep efficiency: 85.8% in the CS group vs 84.4% in the no CS group, P = 0.042; wake after sleep onset: 45.7 min vs 50.6 min, respectively, P = 0.033). In contrast, urinary 6-sulfatoxymelatonin excretion, sleep onset latency, total sleep time, and sleep-mid time did not differ significantly between the CS and no CS groups.

Conclusions

Among a community-dwelling elderly population, CS is significantly associated with objectively measured sleep quality, but urinary levels of melatonin metabolite do not differ between individuals with and without CS. These associations are independent of daily light exposure profiles.

Short-term influence of cataract surgery on circadian biological rhythm and related health outcomes (CLOCK-IOL trial): study protocol for a randomized controlled trial

Background

Light information is the most important cue of circadian rhythm which synchronizes biological rhythm with external environment. Circadian misalignment of biological rhythm and external environment is associated with increased risk of depression, insomnia, obesity, diabetes, cardiovascular disease, and cancer.

Increased light transmission by cataract surgery may improve circadian misalignment and related health outcomes. Although some observational studies have shown improvement of depression and insomnia after cataract surgery, randomized controlled trials are lacking. We will conduct a parallel-group, assessor-blinded, simple randomized controlled study comparing a cataract surgery group at three months after surgery with a control group to determine whether cataract surgery improves depressive symptoms, sleep quality, body mass regulation, and glucose and lipid metabolism.

Methods/Design

We will recruit patients who are aged 60 years and over, scheduled to receive their first cataract surgery, and have grade 2 or higher nuclear opacification as defined by the lens opacities classification system III. Exclusion criteria will be patients with major depression, severe corneal opacity, severe glaucoma, vitreous haemorrhage, proliferative diabetic retinopathy, macular oedema, age-related macular degeneration, and patients needing immediate or combined cataract surgery. After baseline participants will be randomized to two groups. Outcomes will be measured at three months after surgery among the intervention group, and three months after baseline among the control group. We will assess depressive symptoms as a primary outcome, using the short version geriatric depression scale (GDS-15). Secondary outcomes will be subjective and actigraph-measured sleep quality, sleepiness, glycated haemoglobin, fasting plasma glucose and triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, body mass index, abdominal circumference, circadian rhythms of physical activity and wrist skin temperature, and urinary melatonin metabolite. Chronotype and visual function will be assessed using the ‘morningness-eveningness’ questionnaire, the Munich chronotype questionnaire, and the National Eye Institute Visual Function Questionnaire.

Discussion

Although there are potential limitations due to the difference in duration from baseline survey to outcome measurements between two groups, any seasonal effect on the outcome measurement will be balanced as a result of continuous inclusion of participants through the year, and outcomes will be adjusted for day length at outcome measurements at analysis.

Trial registration

UMIN000014559, UMIN Clinical Trials Registry, registered on 15 July 2014.

Protecting the melatonin rhythm through circadian healthy light exposure

Currently, in developed countries, nights are excessively illuminated (light at night), whereas daytime is mainly spent indoors, and thus people are exposed to much lower light intensities than under natural conditions. In spite of the positive impact of artificial light, we pay a price for the easy access to light during the night: disorganization of our circadian system or chronodisruption (CD), including perturbations in melatonin rhythm. Epidemiological studies show that CD is associated with an increased incidence of diabetes, obesity, heart disease, cognitive and affective impairment, premature aging and some types of cancer. Knowledge of retinal photoreceptors and the discovery of melanopsin in some ganglion cells demonstrate that light intensity, timing and spectrum must be considered to keep the biological clock properly entrained. Importantly, not all wavelengths of light are equally chronodisrupting. Blue light, which is particularly beneficial during the daytime, seems to be more disruptive at night, and induces the strongest melatonin inhibition. Nocturnal blue light exposure is currently increasing, due to the proliferation of energy-efficient lighting (LEDs) and electronic devices. Thus, the development of lighting systems that preserve the melatonin rhythm could reduce the health risks induced by chronodisruption. This review addresses the state of the art regarding the crosstalk between light and the circadian system.

Effects of tryptophan-rich breakfast and light exposure during the daytime on melatonin secretion at night

Background

The purpose of the present study is to investigate effects of tryptophan intake and light exposure on melatonin secretion and sleep by modifying tryptophan ingestion at breakfast and light exposure during the daytime, and measuring sleep quality (by using actigraphy and the OSA sleep inventory) and melatonin secretion at night.

Methods

Thirty three male University students (mean ± SD age: 22 ± 3.1 years) completed the experiments lasting 5 days and 4 nights. The subjects were randomly divided into four groups: Poor*Dim (n = 10), meaning a tryptophan-poor breakfast (55 mg/meal) in the morning and dim light environment (<50 lx) during the daytime; Rich*Dim (n = 7), tryptophan-rich breakfast (476 mg/meal) and dim light environment; Poor*Bright (n = 9), tryptophan-poor breakfast and bright light environment (>5,000 lx); and Rich*Bright (n = 7), tryptophan-rich breakfast and bright light.

Results

Saliva melatonin concentrations on the fourth day were significantly lower than on the first day in the Poor*Dim group, whereas they were higher on the fourth day in the Rich*Bright group. Creatinine-adjusted melatonin in urine showed the same direction as saliva melatonin concentrations. These results indicate that the combination of a tryptophan-rich breakfast and bright light exposure during the daytime could promote melatonin secretion at night; further, the observations that the Rich*Bright group had higher melatonin concentrations than the Rich*Dim group, despite no significant differences being observed between the Poor*Dim and Rich*Dim groups nor the Poor*Bright and Rich*Bright groups, suggest that bright light exposure in the daytime is an important contributor to raised melatonin levels in the evening.

Conclusions

This study is the first to report the quantitative effects of changed tryptophan intake at breakfast combined with daytime light exposure on melatonin secretion and sleep quality. Evening saliva melatonin secretion changed significantly and indicated that a tryptophan-rich breakfast and bright light exposure during the daytime promoted melatonin secretion at this time.

Lower melatonin secretion in older females: gender differences independent of light exposure profiles

Background

Melatonin is associated with a variety of diseases in advanced age, including insomnia, depression, and dementia, and its secretion is influenced by light exposure. Although studies in young and middle-aged subjects have shown that females tend to have higher melatonin levels than males, gender differences in melatonin levels among older people remain unclear.

Methods

To determine the gender differences in melatonin levels among older people in home settings, we conducted a cross-sectional study in 528 older people. We measured overnight urinary 6-sulfatoxymelatonin excretion (UME; an index of melatonin secretion), and ambulatory light intensity.

Results

The mean age of females was 1.8 years younger, and average intensity of daytime light exposure was half that in males (P < 0.01). In a univariate comparison, UME was significantly lower in females than in males (P < 0.01). A multivariate model using analysis of covariance showed that log-transformed UME remained significantly lower in females after adjustment for potential confounding factors, including age and daytime and nighttime light exposure profiles (males vs. females: 1.90 vs. 1.73 log µg; adjusted mean difference 0.17 log µg [95% confidence interval [CI] 0.02–0.32]; P = 0.02). This result indicates that older females have 18.4% (95% CI, 2.2–37.4%) lower UME than older males.

Conclusions

Older females have significantly lower UME than older males, an association which is independent of light exposure profiles in home settings. Our findings may be useful as basic data for further research to investigate gender differences in several diseases associated with melatonin in the elderly.

Effects of exercise with or without light exposure on sleep quality and hormone reponses

[Purpose]

The objectives of the present study were to determine the effect of sun exposure and aerobic exercise on quality of sleep and investigate sleep-related hormonal responses in college-aged males.

[Methods]

In this study, the cross-over design was utilized. The subjects (N = 10) without any physical problems or sleep disorders participated in the experimental performed 4 protocols in only sun exposure (for 30 minutes, EG1) protocol, only aerobic exercise (walking and jogging for 30 minutes, EG2) protocol, aerobic exercise with sun exposure (EG3) protocol, and control (no exercise and no sun exposure, EG4) protocol. Each protocol was 5 times per week with one-week break (wash-out period) between protocols to prevent the effects of the previous protocol. Total test period was should be 7 weeks (one week of protocol and one week of break). Before and after each aerobic exercise session, the subjects completed stretching to warm up for 5 to 10 minutes. Surveys consisting of (bedtime, wake-up time, sleep onset latency, and (Pittsburgh Sleep Quality Index (PSQI) were obtained before the test and after each protocol. After each protocol, the following sleep-related hormonal responses were measured: blood concentrations of melatonin, cortisol, epinephrine, and norepinephrine. One-way ANOVA was used to determine differences between protocols. Statistical significance was set at p < 0.05.

[Results]

Bedtime of EG4 was significantly later than that of the EG1 or EG3. Wake-up time in the EG4 was significantly later than that of the EG1 or the EG3. Sleep onset latency in the EG4 was longer than that of the EG3. The quality of sleep in the EG4 was lower than that of the EG3. Sleep cycle in the EG4 was significantly shorter than that of the EG1. Blood melatonin concentrations of the EG3 was significantly higher than that of the EG4. There were no significant differences in blood concentrations of cortisol, epinephrine, or norepinephrine among protocols, with the order from the lowest to the highest values of EG1 < EG2 < EG3 < EG4.

[Conclusion]

The present data found that EG1 and EG3 showed positive sleep-related hormonal responses, sleep habits, and quality of sleep, indicating that sun exposure or exercise with sun exposure may improve the physical status and quality of life.

The Nature of Sleep in 10 Bedridden Elderly Patients With Disorders of Consciousness in a Japanese Hospital

No previous study has satisfactorily clarified the nature of sleep in elderly bedridden people with disorders of consciousness (DOC). The objective of the present study was to clarify the sleep states of 10 elderly bedridden patients with DOC in a Japanese hospital to facilitate provision of evidence-based nursing care and appropriate adjustment of patients’ environments. Nocturnal polysomnography recordings were analyzed according to the standard scoring criteria, and the patients’ sleep stages and quality were investigated. Of the 10 patients, 9 showed slow wave sleep (SWS), 4 showed very high values for sleep efficiency (96–100%), and in 3 of these patients, the percentage of SWS was ≥ 20%. Furthermore, three of these four patients had 200 or more changes in sleep stage. Although the mechanism is unknown, the amount of SWS combined with the value of sleep efficiency suggests that the quality of sleep is poor in elderly bedridden patients with DOC. Further study is needed to determine better indicators of good sleep in this population.

Melatonin regulation of biliary functions

The intrahepatic biliary epithelium is a three-dimensional tubular system lined by cholangiocytes, epithelial cells that in addition to modify ductal bile are also the targets of vanishing bile duct syndromes (i.e., cholangiopathies) such as primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) that are characterized by the damage/proliferation of cholangiocytes. Cholangiocyte proliferation is critical for the maintenance of the biliary mass and secretory function during the pathogenesis of cholangiopathies. Proliferating cholangiocytes serve as a neuroendocrine compartment during the progression of cholangiopathies, and as such secrete and respond to hormones, neurotransmitters and neuropeptides contributing to the autocrine and paracrine pathways that regulate biliary homeostasis. The focus of this review is to summarize the recent findings related to the role of melatonin in the modulation of biliary functions and liver damage in response to a number of insults. We first provide a general background on the general function of cholangiocytes including their anatomic characteristics, their innervation and vascularization as well the role of these cells on secretory and proliferation events. After a background on the synthesis and regulation of melatonin and its role on the maintenance of circadian rhythm, we will describe the specific effects of melatonin on biliary functions and liver damage. After a summary of the topics discussed, we provide a paragraph on the future perspectives related to melatonin and liver functions.

Melatonin: buffering the immune system

Melatonin modulates a wide range of physiological functions with pleiotropic effects on the immune system. Despite the large number of reports implicating melatonin as an immunomodulatory compound, it still remains unclear how melatonin regulates immunity. While some authors argue that melatonin is an immunostimulant, many studies have also described anti-inflammatory properties. The data reviewed in this paper support the idea of melatonin as an immune buffer, acting as a stimulant under basal or immunosuppressive conditions or as an anti-inflammatory compound in the presence of exacerbated immune responses, such as acute inflammation. The clinical relevance of the multiple functions of melatonin under different immune conditions, such as infection, autoimmunity, vaccination and immunosenescence, is also reviewed.

The management of sleep and circadian disturbance in patients with dementia

Sleep and circadian disturbances are common among patients with dementia. Symptomatic manifestations vary according to dementia subtype, with one commonly shared pattern--the irregular sleep-wake rhythm (ISWR), a circadian disorder characterized by an absence of the sleepwake cycle’s circadian synchronization. Hypothesized mechanisms of circadian rhythm disturbance include suprachiasmatic nucleus (SCN) circadian pacemaker damage, pineal gland and melatonin secretion alterations, and reduced zeitbeigers and decreased input to the SCN. Management options include prescribed sleep/wake scheduling, light therapy, melatonin, physical and social activity, and mixed modality. The mixed-modality approach is the most effective method in treating ISWR. Pharmacologic interventions are controversial, with no evidence supporting their effectiveness while associated with multiple side effects. They should be used with caution and only be considered as short-term therapy. All treatment strategies should be individualized to achieve the best outcomes.

Daily rhythms of the sleep-wake cycle

The amount and timing of sleep and sleep architecture (sleep stages) are determined by several factors, important among which are the environment, circadian rhythms and time awake. Separating the roles played by these factors requires specific protocols, including the constant routine and altered sleep-wake schedules. Results from such protocols have led to the discovery of the factors that determine the amounts and distribution of slow wave and rapid eye movement sleep as well as to the development of models to determine the amount and timing of sleep. One successful model postulates two processes. The first is process S, which is due to sleep pressure (and increases with time awake) and is attributed to a 'sleep homeostat'. Process S reverses during slow wave sleep (when it is called process S'). The second is process C, which shows a daily rhythm that is parallel to the rhythm of core temperature. Processes S and C combine approximately additively to determine the times of sleep onset and waking. The model has proved useful in describing normal sleep in adults. Current work aims to identify the detailed nature of processes S and C. The model can also be applied to circumstances when the sleep-wake cycle is different from the norm in some way. These circumstances include: those who are poor sleepers or short sleepers; the role an individual's chronotype (a measure of how the timing of the individual's preferred sleep-wake cycle compares with the average for a population); and changes in the sleep-wake cycle with age, particularly in adolescence and aging, since individuals tend to prefer to go to sleep later during adolescence and earlier in old age. In all circumstances, the evidence that sleep times and architecture are altered and the possible causes of these changes (including altered S, S' and C processes) are examined.

Neurochemical and neuropharmacological aspects of circadian disruptions: an introduction to asynchronization

Circadian disruptions are common in modern society, and there is an urgent need for effective treatment strategies. According to standard diagnostic criteria, most adolescents showing both insomnia and daytime sleepiness are diagnosed as having behavioral-induced sleep efficiency syndrome resulting from insomnia due to inadequate sleep hygiene. However, a simple intervention of adequate sleep hygiene often fails to treat them. As a solution to this clinical problem, the present review first overviews the basic neurochemical and neuropharmachological aspects of sleep and circadian rhythm regulation, then explains several circadian disruptions from similar viewpoints, and finally introduces the clinical notion of asynchronization. Asynchronization is designated to explain the pathophysiology/pathogenesis of exhibition of both insomnia and hypersomnia in adolescents, which comprises disturbances in various aspects of biological rhythms. The major triggers for asynchronization are considered to be a combination of light exposure during the night, which disturbs the biological clock and decreases melatonin secretion, as well as a lack of light exposure in the morning, which prohibits normal synchronization of the biological clock to the 24-hour cycle of the earth and decreases the activity of serotonin. In the chronic phase of asynchronization, involvement of both wake- and sleep-promoting systems is suggested. Both conventional and alternative therapeutic approaches for potential treatment of asynchronization are suggested.