Dark Night Research Articles

Dark night of the soul: the lived experience and meaning of mental health crisis

Dark night of the soul: the lived experience and meaning of mental health crisis

Camouflage or Coincidence? Investigating the Effects of Spatial and Temporal Environmental Features on Feral Cat Morphology in Tasmania.

Variations in coat morphology are well documented among felids and are theorised to aid in camouflage during stalk and ambush hunting. A diverse array of coat types has arisen in Felis catus (feral cats) through domestication and subsequent selective breeding. This species has successfully spread across Australia over the past 200 years, raising the question of whether any specific coat types offer an adaptive advantage. We used 24,657 camera-trap images of feral cats in Tasmania, Australia, and assigned each cat observation a coat colour and pattern. We analysed these data to examine how different spatial features affect the modal coat type present at a site. We also tested if cats with differing coat types were active on different days in response to temporal features, including moon luminosity (full or new). Elevation was positively associated with the presence of orange (odds ratio = 2.5, 97.5% confidence interval = 1.5, 4.4) and tortoiseshell (odds ratio = 4.1, CI = 1.6, 10.5) cats, while blotched brown cats were negatively associated with elevation (odds ratio = 0.64, CI = 0.5, 0.9), relative to black cats. Brown mackerel cats were more common in eucalypt and rainforests (odds ratio = 1.9, CI = 1.1, 3.3), as well as sites with a higher FPAR (odds ratio = 1.3, CI = 1.1, 1.6). All coat types were 1.2-2 times more likely to be active on nights with a new moon, except for orange cats who were equally active regardless of moon luminosity (odds ratio = 0.94, CI = 0.62, 1.42). Our results indicate that coat types are equally successful across Tasmania, perhaps owing to naïve prey or limited predator competition. The high activity of orange cats irrespective of moon phase may be reflective of the male cat's tendency to patrol territory, as opposed to favouring dark nights for hunting. Future studies should consider comparing the coat types found in feral cats to adjacent domestic populations, and against a wider array of habitat types to further investigate the potential for selective pressure on feral cat coat types in Australia.

Bataille and Wittgenstein: on mysticism, silence, and inner experience

ABSTRACT Despite differences, Georges Bataille, theorist of non-knowledge and atheology, and Ludwig Wittgenstein, the Austrian logician, share specific parallels regarding their understandings of language and mystical experience. For both, mystical experience pushes beyond conventional discourse. Using analogous elements of critical and mystical discourse, each express rather antiphilosophical, spiritual visions. Still, Wittgenstein’s deeply private and agnostic Christianity sharply contrasts Bataille’s own atheological experience of the death of God. Where Bataille’s mysticism challenges rationality, Wittgenstein’s instead expresses the numinous world as such, shedding light on the dark night of Bataille and the specific character of ‘inner experience’. Where Wittgenstein advocates either clarity of expression or silence, however, the transgressive and poetic syntax of Bataille, alongside his evocative and erotic usage of imagery and metaphor, instead presses precisely against the impossibility for words that Wittgenstein’s thinking forecloses. Silence, like evil and poetry for Bataille, is active and imperative to communication, opening itself against the closure of reason. Relative to Wittgenstein and Christianity’s ascent to knowledge and awareness then, Bataille instead dives down deep into the body and night of nonknowledge. In this way, paradoxically, Bataille’s atheological writings approach a new summit of communication only attainable in the absence of God.

Book Review: Madhouse at the End of the Earth: The Belgica’s Journey into the Dark Antarctic Night Sancton Julian

Book Review: <i>Madhouse at the End of the Earth: The Belgica’s Journey into the Dark Antarctic Night</i> Sancton Julian

MONITORING OF LIGHT POLLUTION IN THE TRANSCARPATHIAN REGION

Light pollution first gained attention when people realized they could no longer see the night sky as they once did due to excess visible and ultraviolet light from cities. However, in recent years, it has become clear that artificial night lighting worries not only astronomers. Studies have shown that artificial night lighting harms a variety of animals. To preserve the natural darkness of the sky in the world, parks of the dark (or starry) sky are created, which are the areas of a unique natural environment that protect the natural night darkness from pollution by artificial light. They are the equivalent of nature reserves — territories with exceptional natural value. They perform protective functions for the darkest corners of our planet, where the night environment is not dis- turbed by artificial light. These parks perform not only ecological but also educational functions. Darkness protection is slowly being incorporated into existing conservation areas such as national parks. Darkness is a natural resource that needs protection. In 2016, Transcarpathian Dark Sky Park was created. For its registration and entry into the International Association of Dark Sky Parks, the brightness of the night sky was measured in different places in this park to determine the state of light pollution in this area. The results of the measurements fully satisfied the requirements for dark sky parks. In all places of the Transcarpath- ian Dark Sky Park where we performed measurements, the average value of the background of the night sky was ~21.50 mag/ arcsec 2 . In 2021, an application for registration of Transcarpathian Dark Sky Park in the International Association of Dark Sky Parks was accepted. Research into the state of light pollution on the outskirts of the Dark Sky Park is also ongoing, namely at two optical observation stations — Uzhhorod and Derenivka. The results of changes in the background of the night sky in these places over a 40-year time interval are presented.

Phototrap‐assessed diel activity of Cerambyx cerdo and Cerambyx welensii sympatric populations in the wild: Does extreme drought boost diurnality?

Abstract Longhorn beetles (Cerambycidae) are a very diverse group whose species vary greatly in morphology and behaviour, particularly in diel activity. The type genus Cerambyx includes two large oak‐ling sympatric species (Cerambyx cerdo and Cerambyx welensii) that exhibit a crepuscular/nocturnal (dim‐light) lifestyle, but their actual diel activity remains largely unclear. We used phototraps in the wild to assess if diel activity depended on either species, sex or annual meteorology. Phototraps were highly effective, and the imaged activities were representative of beetles' life, including interactions with some vertebrate species. Both longhorns exhibited roughly similar crepuscular/nocturnal behaviour, with daytime activity being usually residual or erratic. Diel activity increased sharply just before dusk, peaked between dusk and early dark night (23:00–2:00 h), and then dropped progressively until disappearing at dawn. Diel activity was sexually dimorphic in C. welensii, as in some years females tended to be active earlier than males. Distinctly, in 2022, the warmest and driest year recorded in the study area, diel activity curves were flatter and wider, with C. cerdo activity increasing in the late afternoon (19:00–21:30 h) and C. welensii in the second half of the night (3:00–6:00 h). Furthermore, both species boosted daytime activity (diurnality) by more than three times, and diurnality also increased over the season that year. We finally hypothesise that, under the current climate change scenario, extreme droughts impact diel activity in these species, particularly boosting diurnality, in an attempt to locate water/food sources to counteract body dehydration.

Resistance to Change or Transformation After Involuntary Unemployment and Underemployment: A Theoretical Model

Significant changes in workplace strategy or economic instability can lead individuals into emotional and spiritual crises, triggering identity transformations. This paper explores the effects of involuntary unemployment, underemployment, compromised employment, and mandatory retirement, referred to as involuntary second-order employment disruptions, on personal identity. Drawing from theories of quantum personal change and positive psychology, the paper discusses how these changes can lead to emotional and spiritual distress, akin to a “dark night of the soul,” potentially resulting in posttraumatic transformation. The transition through this crisis involves stages of resistance and adaptation, ultimately leading to a profound shift in identity and purpose. The process includes disengagement, disidentification, disenchantment, and disorientation, which can create significant psychological challenges, and involuntary opportunities for spiritual growth and self-actualization. The paper proposes that these employment disruptions are catalysts for deep personal transformation, highlighting the importance of managing such transitions effectively to foster resilience and positive outcomes.

Personal light exposure patterns and incidence of type 2 diabetes: analysis of 13 million hours of light sensor data and 670,000 person-years of prospective observation

Light at night disrupts circadian rhythms, and circadian disruption is a risk factor for type 2 diabetes. Whether personal light exposure predicts diabetes risk has not been demonstrated in a large prospective cohort. We therefore assessed whether personal light exposure patterns predicted risk of incident type 2 diabetes in UK Biobank participants, using ∼13 million hours of light sensor data. Participants (N=84,790, age (M ± SD)=62.3±7.9 years, 58% female) wore light sensors for one week, recording day and night light exposure. Circadian amplitude and phase were modeled from weekly light data. Incident type 2 diabetes was recorded (1997 cases; 7.9±1.2 years follow-up; excluding diabetes cases prior to light-tracking). Risk of incident type 2 diabetes was assessed as a function of day and night light, circadian phase, and circadian amplitude, adjusting for age, sex, ethnicity, socioeconomic and lifestyle factors, and polygenic risk. Compared to people with dark nights (0-50th percentiles), diabetes risk was incrementally higher across brighter night light exposure percentiles (50-70th: multivariable-adjusted HR=1.29 [1.14-1.46]; 70-90th: 1.39 [1.24-1.57]; and 90-100th: 1.53 [1.32-1.77]). Diabetes risk was higher in people with lower modeled circadian amplitude (aHR=1.07 [1.03-1.10] per SD), and with early or late circadian phase (aHR range: 1.06-1.26). Nightlight and polygenic risk independently predicted higher diabetes risk. The difference in diabetes risk between people with bright and dark nights was similar to the difference between people with low and moderate genetic risk. Type 2 diabetes risk was higher in people exposed to brighter night light, and in people exposed to light patterns that may disrupt circadian rhythms. Avoidance of light at night could be a simple and cost-effective recommendation that mitigates risk of diabetes, even in those with high genetic risk. Australian Government Research Training Program.

Semantic potential of L. Andreev’s story “Kusaka”

INTRODUCTION. The research will be useful not only to linguists and literary scholars, but also to literature teachers, since the works of L. Andreev are included in the school curriculum. The purpose of the work is to identify the semantic potential of L. Andreev’s story “Kusaka”. The relevance of the study is due to the need to study L. Andreev’s literary texts for modern philological science from the point of view of identifying the ability of units of different levels that are interconnected to act as markers of the mythical-poetic code.MATERIALS AND METHODS. The material of this work is the text of L. Andreev’s story “Kusaka”, which is a system of multi-level units, the analysis of which contributes to a deeper penetration into the author’s artistic intention. The work uses both general scientific and special linguistic methods: the method of linguistic observation and description, etymological, word-formation, onomastic, contextual, stylistic and linguocultural types of analysis.RESULTS AND DISCUSSION. It is shown that the literary text of L. Andreev is characterized by the interrelation of units of different levels, revealing the mythopoetic basis of the story, represented by the oppositions friend–foe, ligh–darkness, sound–silence. The dominant elements of the story are the lexemes house, yard, garden, sun, darkness. The diminutives used by the author when describing the girl and the dog create the image of a toy that is interesting and desirable in the present, but may be abandoned in the future due to loss of interest in it. Proper names (zoonyms Zhuchka, Kusaka, Kusachka and anthroponyms Lelya, Ilyusha, Dogaevs) and their absence have a special meaning.CONCLUSION. As in most of L. Andreev’s works, the story “Kusaka”, demonstrating the struggle of light with darkness, presents the path of gaining (Kusaka) and losing the soul (Lyolya and other people who for some reason are called kind). All this happens against the background of natural cyclicality – winter– spring–summer–autumn–... correlate with the natural processes of birth-development-old agedeath. Coming after the departure of the people who abandoned Kusaka, who again turned into just a nameless dog, the hopeless dark night becomes a symbol of lost hope, lost happiness.

Park lighting after dark – is it a route or a place? How people feel in park nightscapes (experiment)

The objective of our study was to verify: (1) whether adding ambient lighting in addition to path lighting has a positive impact on preferences, sense of safety and related feelings experienced by park visitors after dusk (H1) and whether this impact is differentiated by the features of the space (H2); (2) what features of the park space may influence the feelings tested (RQ1).For this purpose, we conducted an experiment in the Botanical Garden in Wrocław, where 114 study participants – randomly divided into two groups (experimental and control) – assessed nightscapes based on 13 variables (feelings). The experimental factor was the addition of ambient lighting (in addition to path lighting also present for the control group). The experiment was based on assessments made in three different places in the park – an open space, semi-open space and non-closed space. Thanks to this, we were able to check whether the features of the space differentiate the effects of the experimental factor and then consider their impact on people's feelings.The research found that the impact of the experimental factor (ambient light) is not obvious – it was only apparent in some cases. This factor increased preference for corridor landscapes (semi-open and semi-closed space), but lowered preference in the open landscape. The experimental factor had the strongest effects in the semi-closed, least lit space, and enhanced preferences, surprise and fascination.Moreover, comparison of the ratings of these three places showed that some spaces were rated as the safest while others were assessed as the most attractive. The safest turned out to be the semi-open space with typical park lighting, with the highest path illumination intensity, whereas the least safe was the semi-closed space with the least lighting. When it came to most of the other dimensions related to attractiveness and desire to stay in the area (mystery, contact with the surroundings, willingness to spend time there, surprise, fascination and contemplation), the place with an open view, visually attractive landscape and subtle linear point lighting was rated the highest. The remaining spaces were rated lower.The findings of the experiment indicate that (1) adding light does not always increase preference for a particular space – sometimes it lowers it, thus indicating the benefits of darkness and natural night light in park landscapes; (2) there are differences between the features of safe nightscapes and attractive and leisurely landscapes.

Dim light at night shifts microglia to a pro-inflammatory state after cerebral ischemia, altering stroke outcome in mice

Circadian rhythms are endogenous biological cycles that regulate physiology and behavior and are set to precisely 24-h by light exposure. Light at night (LAN) dysregulates physiology and function including immune response; a critical component that contributes to stroke pathophysiological progression of neuronal injury and may impair recovery from injury. The goal of this study is to explore the effects of dim LAN (dLAN) in a murine model of ischemic stroke to assess how nighttime lighting from hospital settings can affect stroke outcome. Further, this study sought to identify mechanisms underlying pathophysiological changes to immune response after circadian disruption. Male and female adult Swiss Webster (CFW) mice were subjected to transient or permanent focal cerebral ischemia, then were subsequently placed into either dark night conditions (LD) or one night of dLAN (5 lx). 24 h post-stroke, sensorimotor impairments and infarct sizes were quantified. A single night of dLAN following MCAO increased infarct size and sensorimotor deficits across both sexes and reduced survival in males after 24 h. Flow cytometry was performed to assess microglial phenotypes after MCAO, and revealed that dLAN altered the percentage of microglia that express pro-inflammatory markers (MHC II+ and IL-6) and microglia that express CD206 and IL-10 that likely contributed to poor ischemic outcomes. Following these results, microglia were reduced in the brain using Plexxikon 5622 (PLX 5622) a CSFR1 inhibitor, then the mice received an MCAO and were exposed to LD or dLAN conditions for 24 h. Microglial depletion by PLX5622 resulted in infarct sizes that were comparable between lighting conditions. This study provides supporting evidence that environmental lighting exacerbates ischemic injury and post-stroke mortality by a biological mechanism that exposure to dLAN causes a fundamental shift of activated microglial phenotypes from beneficial to detrimental at an early time point after stroke, resulting in irreversible neuronal death.

Effect of textile colour on vector mosquito host selection: a simulated field study in Mali, West Africa.

The effect of clothing colour on the biting rates of different vector mosquito species is not well understood. Studies under tropical field conditions are lacking. This study aimed to determine the influence of clothing colours on mosquito biting rates in rural and suburban settings in West Africa. We performed a simulated field study in a suburban and a rural site in Mali using Mosquito-Magnet traps utilizing CO2 and other attractants, which were covered with black, white, and black/white striped textile sheets covers. These targets operated continuously for 10 consecutive days with bright nights (around full moon) and 10 consecutive days with dark nights (around new moon). Trapped mosquitoes were collected and catch rates counted hourly. Mosquitoes were morphologically identified to the species complex level (Anopheles gambiae s.l. and Culex pipiens s.l.) or species level (Aedes aegypti). A subset of Anopheles specimens were further identified by molecular methods. Under bright-night conditions, An. gambiae s.l. was significantly more attracted to black targets than to white and striped targets; during dark nights, no target preference was noted. During bright nights, Cx. pipiens s.l. was significantly more attracted to black and striped targets than to white targets; a similar trend was noted during dark nights (not significant). For day-active Ae. aegypti, striped targets were more attractive than the other targets and black were more attractive than white targets. The study firstly demonstrated that under field conditions in Mali, West Africa, mosquito catch rates were influenced by different clothing colours, depending on mosquito species and light conditions. Overall, light colours were least attractive to host-seeking mosquitoes. Using white or other light-coloured clothing can potentially reduce bite exposure and risk of disease transmission in endemic tropical regions.

Role of Melatonin in Viral, Bacterial and Parasitic Infections.

In all mammals, the circulating pool of MLTs is synthesized in the pineal gland during the night's darkness hours. Its main function is synchronizing the organism in the photoperiod. In contrast, extra-pineal MLT is synthesized in peripheral organs, does not follow any circadian rhythm or circulate, and plays a detoxifying and cytoprotective role. Circulating MLT may stimulate both innate and acquired immune responses through its circadian action and by activating high-affinity receptors on immunocompetent cells. Extra-pineal MLT may have antioxidant and anti-inflammatory effects that dampen the innate immune response. These two seemingly divergent roles may be considered to be two sides of the same coin. In fact, the integration of both circulating and extra-pineal MLT functions might generate a balanced and effective immune response against microbial pathogens. The studies described in this review investigated the effects of exogenous MLT in various models of infectious diseases using extremely different doses and treatment schedules. None of them evaluated the possibility of integrating the non-circadian anti-inflammatory effect with the circadian immunoenhancing action of MLT. As a consequence, in spite of the fact that most studies agree that MLT has a beneficial effect against infections, it seems difficult to draw any definite conclusion about its possible therapeutic use.

Effects of dim light at night in C57BL/6 J mice on recovery after spinal cord injury

Spinal cord injury (SCI) can cause long-lasting locomotor deficits, pain, and mood disorders. Anatomical and functional outcomes are exacerbated by inflammation after SCI, which causes secondary damage. One promising target after SCI is manipulating the circadian system, which optimizes biology and behavior for time of day – including neuroimmune responses and mood-related behaviors. Circadian disruption after SCI is likely worsened by a disruptive hospital environment, which typically includes dim light-at-night (dLAN). Here, we hypothesized that mice subjected to SCI, then placed in dLAN, would exhibit worsened locomotor deficits, pain-like behavior, and anxiety-depressive-like symptoms compared to mice maintained in light days with dark nights (LD). C57BL/6 J mice received sham surgery or moderate T9 contusion SCI, then were placed permanently in LD or dLAN. dLAN after SCI did not worsen locomotor deficits; rather, SCI-dLAN mice showed slight improvement in open-field locomotion at the final timepoint. Although dLAN did not alter SCI-induced heat hyperalgesia, SCI-dLAN mice exhibited an increase in mechanical allodynia at 13 days post-SCI compared to SCI-LD mice. SCI-LD and SCI-dLAN mice had similar outcomes using sucrose preference (depressive-like) and open-field (anxiety-like) tests. At 21 dpo, SCI-dLAN mice had reduced preference for a novel juvenile compared to SCI-LD, implying that dLAN combined with SCI may worsen this mood-related behavior. Finally, lesion size was similar between SCI-LD and SCI-dLAN mice. Therefore, newly placing C57BL/6 J mice in dLAN after SCI had modest effects on locomotor, pain-like, and mood-related behaviors. Future studies should consider whether clinically-relevant circadian disruptors, alone or in combination, could be ameliorated to enhance outcomes after SCI.

Night sky brightness trends above Zagreb, 2012–2022

The night sky brightness at the RGN site (near the centre of Zagreb, Croatia) was monitored from January 2012 to August 2022. The first data set, covering the period 2012 to 2017, has already been analysed and the conclusions were published in Andreić (2018). The main conclusions are repeated here for comparison and completeness. The results of the analysis of the second dataset, covering the period from January 2018 to July 2022, are reported here. The first data analysis showed that the average night sky brightness did not change significantly from 2012 to 2017, excluding differences due to annual variations in meteorological parameters. The second data set (2018 to 2022) showed a slight decrease in night sky brightness compared to the first data set. The difference is small, about 0.2 mag/arcsec2 (mean values). In the second data set, there is a trend toward darker nights in later years that began three or four years ago (around 2019 or 2020). It is attributed to the modernisation of the public lighting network, where old, often very poor lighting fixtures are slowly being replaced by modern LED lighting fixtures, and to the effects of climatic changes leading to warmer winters with more clear nights.

“Reading”, “listening” and sound, light environment

Sound is always an important medium for passing on knowledge and skills as well as for communicating information. Reading accompanies the use of the brain in the silent reading of words, an act that transforms textual information into verbal information. People can “listen” and “read” in a dark or low light environment. Learning and thinking in a quiet, dark environment is not only conducive to the formation of innovative thinking, but also the inheritance of ancient ideas of health and wisdom. Modern disciplines follow the human perception mechanism and advocate concepts of “Quiet Area” (in soundscape discipline) and “Dark Night Sky” (in lightscape discipline). It is in accordance with the ancients preference of thinking and learning in a “quiet, dark environment”, which is consistent with the law of the matter and the origin of things. This also reflects the integration of human life wisdom and modern science.

Influence of Building Layout and Weather Conditions on Air Traffic Services

I Gusti Ngurah Rai International Airport is one of the busiest airports in Indonesia that serves a variety of flights, ranging from scheduled, unscheduled, cargo, and military, to recreational flights. All flights are regulated by the Air Traffic Controller which is divided into two units, namely the Aerodrome Control Tower and Approach Control Surveillance. The Aerodrome Control Tower has the responsibility of regulating flight traffic in the "vicinity of aerodrome" area. From the tower, ATC must be able to monitor all movements of flight operations in the area of responsibility. However, at the I Gusti Ngurah Rai Airport tower, several things can affect ATC's view in monitoring the movement of flight operations, namely airport buildings that block several parking stands, dark night conditions in the maneuvering area, and extreme weather. Of course, these problems will also affect the performance of ATC in providing flight traffic services. In addition, it can cause doubts in ATC in making decisions for aircraft that are being handled. This research aims to analyze the problem of ATC's limited view in monitoring the movement of flight operations in its area of responsibility. The research method used is qualitative with data collection techniques in the form of observation, literature study, interviews, and documentation. The development of Advanced Surface Movement Guidance and Control System that can monitor the movement of flight operations in various conditions can be one solution to the problem. In addition, the installation of CCTV in several areas that are not visible from the tower can also assist ATC in monitoring the movement of flight operations in the area. The results of this study are expected to assist ATC in monitoring the movement of flight operations both in dark night conditions and extreme weather. The author also hopes that the results of this study can be useful in improving organized and efficient flight traffic services at I Gusti Ngurah Rai International Airport.

Assisting refugee survivors of torture and trauma: An existential perspective.

Consistent exposure to refugee narratives of trauma and torture can profoundly impact trauma therapists. This secondary analysis reanalyzed data from a narrative inquiry investigating the lived experiences of refugee trauma therapists. We aimed to explore emergent concerns through an existential lens to enrich understanding and provide additional insights into the lived experiences of these individuals. Participants in this purposive sample (N = 19) were therapists who had provided interventions to refugees for 2-34 years. Narrative construction, theory-guided data analysis, and memo writing were used to reanalyze data generated by semistructured interviews augmented by photo elicitation. The findings indicate that being forced to reevaluate familiar beliefs consequent to one's professional roles induced intense existential moments, described as "a dark night of the soul," "the paradox of life and death," "uncanny feelings of not being at home," and "a falling." Acknowledging the complexities of the field, an existential framework to assist refugee trauma therapists in metabolizing and living with the professional challenges they encounter instead of focusing on alleviating decontextualized symptoms of distress is recommended. Research to inform requirements of the space to enable refugee trauma therapists to share their concerns and facilitate transitions toward more authentic, nonevasive sense of "being-in-the-world" is suggested.

“The night of nothingness”. New dimensions of the experience of the Dark Night in the autobiography of Thérèse of Lisieux

“The night of nothingness”. New dimensions of the experience of the Dark Night in the autobiography of Thérèse of Lisieux

Tailored lighting intervention (TLI) for improving sleep-wake cycles in older adults living with dementia.

Introduction: Sleep disturbance is a hallmark of Alzheimer's disease and related dementias, and caregiver stress caused by patients' nighttime wandering, injuries, and agitation are frequently at the root of decisions to move them to assisted living facilities, where typically dim institutional lighting can further exacerbate their sleep problems. This study explored the effects of a circadian-effective lighting intervention on actigraphic sleep measures and subjective assessments of sleep disturbance, depression, and sleep-disturbed behaviors. Methods: Fourteen older adult (≥60years) participants (11 females, mean age = 84.1 [SD 8.9]), all diagnosed with moderate to severe dementia and sleep disturbance, were recruited from 3 assisted living and memory care facilities. Following a crossover, placebo-controlled design, 3 different lighting modes were used to deliver high levels of circadian stimulus to the participants' eyes for two 8-week intervention periods in a counter balanced order with a 4-week washout between the study's 2 conditions (dim light control vs. active intervention). Actigraphy and questionnaire data were collected over 7-day assessment periods that preceded (baseline weeks 1 and 9) and concluded (post-intervention week 9 and 22) the intervention periods. Actigraphic outcomes included sleep duration, sleep time, sleep efficiency, sleep start time, and sleep end time. Subjective assessments included the Cornell Scale for Depression in Dementia (CSDD), Pittsburgh Sleep Quality Index (PSQI), and Sleep Disorders Inventory (SDI) instruments. Results: Under the active condition, sleep duration significantly (p = 0.018) increased and sleep start time significantly (p = 0.012) advanced after the intervention compared to baseline. Also under the active condition, PSQI (p = 0.012), CSDD (p = 0.007), Sleep Disorders Inventory frequency (p = 0.015), and SDI severity (p = 0.015) scores were significantly lower after the intervention compared to baseline. Discussion: This study demonstrates that a circadian-effective lighting intervention delivering bright days and dark nights improves measures of sleep and mood in dementia patients living in controlled environments.