Light exposure and its applications in human health.

Light exposure has been proven to have a significant impact on human health. As a result, researchers are increasingly exploring its potential benefits and drawbacks. With advancements in understanding light and the manufacturing of light sources, modern health lighting has become widely utilized in daily life and plays a critical role in the prevention and treatment of various illnesses. The use of light in healthcare is a global trend, with many countries actively promoting the development and application of relevant scientific research and medical technology. This field has gained worldwide attention and support from scientists and doctors alike. In this review, we examine the application of lighting in human health and recent breakthroughs in light exposure related to pathology, therapeutic strategies, molecular changes, and more. Finally, we also discuss potential future developments and areas of application.

Long-term effects of environmental dynamic lighting on sleep-wake rhythm, mood and behaviour in older adults with intellectual disabilities.

BACKGROUND: Sleep-wake problems and depressive symptoms are common in people with intellectual disabilities (IDs) and are thought to be related to the unstable sleep-wake rhythm in this population. Previously, we showed that after increasing environmental light exposure, mid-sleep and sleep onset advanced, and mood improved over a period of 14 weeks after installing environmental dynamic light installations in the living room of people with IDs. We invited participants of that short-term study to take part in the current study on sleep-wake rhythm, mood and behaviour in older adults with IDs 1 year after installing environmental dynamic light installations in the common living rooms of six group homes. METHODS: A pre-post study was performed from October 2017 to February 2019. We included 45 participants (63.5 ± 8.5 years, 67% female) from six group home facilities who provided data at baseline (9, 4 and 1 weeks prior to installing light installations), short term (3, 7 and 14 weeks after installing light installations) and 1 year (54 weeks after installing light installations). Wrist activity was measured with actigraphy (GENEActiv) to derive the primary outcome of interdaily stability of sleep-wake rhythms as well as sleep estimates. Mood was measured with the Anxiety, Depression and Mood Scale. Behaviour was measured with the Aberrant Behaviour Checklist. RESULTS: One year after installing dynamic lighting, we did not find a change in interdaily stability. Total sleep time decreased (ß = -25.40 min; confidence interval: -10.99, -39.82), and sleep onset time was delayed (ß = 25.63 min; confidence interval: 11.18, 40.08). No effect on mood or behaviour was found. CONCLUSIONS: We did not find a change in sleep-wake rhythm, mood or behaviour in older persons with IDs living in care facilities 1 year after installing the light. We did find evidence for a long-term effect on sleep duration and sleep timing. The results have to be interpreted with care as the current study had a limited number of participants. The need for more research on the long-term effects of enhancing environmental light in ID settings is evident.

Differential synthetic illumination based on multi-line detection for resolution and contrast enhancement of line confocal microscopy.

Line confocal (LC) microscopy is a fast 3D imaging technique, but its asymmetric detection slit limits resolution and optical sectioning. To address this, we propose the differential synthetic illumination (DSI) method based on multi-line detection to enhance the spatial resolution and optical sectioning capability of the LC system. The DSI method allows the imaging process to simultaneously accomplish on a single camera, which ensures the rapidity and stability of the imaging process. DSI-LC improves X- and Z-axis resolution by 1.28 and 1.26 times, respectively, and optical sectioning by 2.6 times compared to LC. Furthermore, the spatially resolved power and contrast are also demonstrated by imaging pollen, microtubule, and the fiber of the GFP fluorescence-labeled mouse brain. Finally, Video-rate imaging of zebrafish larval heart beating in a 665.6 × 332.8 µm2 field-of-view is achieved. DSI-LC provides a promising approach for 3D large-scale and functional imaging in vivo with improved resolution, contrast, and robustness.

Supplementation of ambient lighting with a task lamp improves daytime alertness and cognitive performance in sleep-restricted individuals.

STUDY OBJECTIVES: We examined the impact of adding a single-high-melanopic-illuminance task lamp in an otherwise low-melanopic-illuminance environment on alertness, neurobehavioral performance, learning, and mood during an 8-h simulated workday. METHODS: Sixteen healthy young adults [mean(±SD) age = 24.2 ± 2.9, 8F] participated in a 3-day inpatient study with two 8-h simulated workdays and were randomized to either ambient fluorescent room light (~30 melanopic EDI lux, 50 lux), or room light supplemented with a light emitting diode task lamp (~250 melanopic EDI lux, 210 lux) in a cross-over design. Alertness, mood, and cognitive performance were assessed throughout the light exposure and compared between conditions using linear mixed models. RESULTS: The primary outcome measure of percentage correct responses on the addition task was significantly improved relative to baseline in the supplemented condition (3.15% ± 1.18%), compared to the ambient conditions (0.93% ± 1.1%; FDR-adj q = 0.005). Additionally, reaction time and attentional failures on the psychomotor vigilance tasks were significantly improved with exposure to supplemented compared to ambient lighting (all, FDR-adj q ≤ 0.030). Furthermore, subjective measures of sleepiness, alertness, happiness, health, mood, and motivation were also significantly better in the supplemented, compared to ambient conditions (all, FDR-adj q ≤ 0.036). There was no difference in mood disturbance, affect, declarative memory, or motor learning between the conditions (all, FDR-adj q ≥ 0.308). CONCLUSIONS: Our results show that supplementing ambient lighting with a high-melanopic-illuminance task lamp can improve daytime alertness and cognition. Therefore, high-melanopic-illuminance task lighting may be effective when incorporated into existing suboptimal lighting environments. CLINICAL TRIALS: NCT04745312. Effect of Lighting Supplementation on Daytime Cognition. https://clinicaltrials.gov/ct2/show/NCT04745312.

Association between Ambient Illumination and Cognitive Impairment: A Population-Based Study of Older.

It is well-established that light therapy can alleviate cognitive impairment, and ambient illumination (AI) can quantify the amount of exposure to light. However, the relationship between AI and cognitive impairment has been largely understudied. Objectives. We aimed to examine the cross-sectional associations between AI and impaired cognition using data from the National Health and Nutrition Examination Survey (NHANES) (2011-2013) database. Methods. The correlation between AI and cognitive impairment was analyzed using multivariate logistic regression models. Nonlinear correlations were explored using curve fitting. Results. Multivariate logistic regression yielded an OR of 0.872 (95% CI 0.699, 1.088) for the association between AI and cognitive impairment after adjusting for covariates. Smooth curve fitting showed that the correlation was nonlinear, with an inflection point at 1.22. Conclusions. These results suggested that the level of AI may be linked to cognitive impairment. We found a nonlinear relationship of AI with cognitive impairment.

Evaluating Occupant Light Exposure and Usage Patterns in an Inpatient Behavioral Health Unit.

OBJECTIVE: To (1) evaluate the use case for tunable lighting in inpatient behavioral health, (2) describe differences in staff lighting exposures between static and tunable lighting conditions using wearable sensors, and (3) document occupant lighting control usage patterns. BACKGROUND: Tunable lighting fixtures can vary the amount of light and spectral content, so have been offered as a way to address light and health considerations. Before we can understand potential health benefits of tunable lighting, it is helpful to understand how occupant exposures under tunable lighting differ from those under more traditional lighting systems. METHODS: Tunable lighting benefits and challenges for inpatient behavioral health were carefully detailed during design. Light exposure measurements were recorded at an old site with static fluorescent lighting and a new site with tunable light-emitting diode (LED) lighting. Behavioral health inpatient unit staff participants voluntarily wore a light measurement device to estimate light exposure. At the new site, controls usage data were recorded each time a button was pressed on a lighting control station. RESULTS: While general observations can be made about the data between sites, there is notable variation at both sites depending on the day and hour. Button press data revealed that occupants used the full capability of the tunable lighting system to support different activities and needs. CONCLUSION: Understanding the relationship between occupant well-being and light requires a holistic research approach including thoughtful design accounting for real-world constraints, detailed measurement of light exposure, and understanding how occupants interact and make use of new technology.

Study on the preparation and luminescence properties of SrGe4 O9 :Mn4+ red phosphors for plant illumination.

In this study, SrGe4 O9 :Mn4+ red phosphors for plant illumination were prepared using a high-temperature solid-phase method. The samples were characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), fluorescence spectroscopy, and other techniques. The phase structure, apparent morphology, and luminescence properties of the SrGe4 O9 :Mn4+ red phosphors were investigated. The results indicated that the dopant Mn4+ was incorporated into the matrix structure by substituting some Ge4+ ions without any changes in the crystal structure of the SrGe4 O9 matrix. The samples comprised micron-scale particles and exhibited high purity and uniform distribution of elements. The SrGe4 O9 :Mn4+ phosphors exhibited relatively strong red light emission at 660 nm under the excitation of a 430-nm blue light, and the luminescence intensity was the highest when the Mn4+ doping amount was 1%. Proper doping of Ti4+ or Sn4+ could effectively improve the luminescence intensity of the SrGe4 O9 :Mn4+ phosphors. The light-emitting diode (LED) device packaging showed that the SrGe4 O9 :Mn4+ red phosphors could be used for plant growth illumination.

Impact of Lighting Assessment and Optimization on Participation and Quality of Life in Individuals with Vision Loss.

This pilot study was designed to investigate the effects of a holistic lighting intervention on the quality of life for individuals with low vision. Sixty participants (44 women; median age 69 years) with visual impairment received lighting interventions, including a home visit and consultation in a lighting lab. Assisted by low vision consultants, participants evaluated their performance using the Canadian Occupational Performance Measure (COPM) before and after the intervention. Improvements in visual functioning and quality of life were evaluated using the 39-item National Eye Institute Visual Function Questionnaire (NEI VFQ-39), the Groffman Visual Tracing Test, and the Farnsworth Dichotomous Test (D15). Following the lighting intervention, scores improved for all activities in the COPM (p < 0.01), for near activities and vision-specific role difficulties in the VFQ-39 (p < 0.05), and overall in the D15 test (p < 0.05). These results suggest the intervention provided an effective method for improving the participants' quality of life and performance.

Individual differences in classification images of Mooney faces.

Human face recognition is robust even under conditions of extreme lighting and in situations where there is high noise and uncertainty. Mooney faces are a canonical example of this: Mooney faces are two-tone shadow-defined images that are readily and holistically recognized despite lacking easily segmented face features. Face perception in such impoverished situations-and Mooney face perception in particular-is often thought to be supported by comparing encountered faces to stored templates. Here, we used a classification image approach to measure the templates that observers use to recognize Mooney faces. Visualizing these templates reveals the regions and structures of the image that best predict individual observer recognition, and they reflect the underlying internal representation of faces. Using this approach, we tested whether there are classification images that are consistent from session to session, whether the classification images are observer-specific, and whether they allow for pattern completion of holistic representations even in the absence of an underlying signal. We found that classification images of Mooney faces were indeed non-random (i.e., consistent session from session) within each observer, but they were different between observers. This result is in line with previously proposed existence of face templates that support face recognition, and further suggests that these templates may be unique to each observer and could drive idiosyncratic individual differences in holistic face recognition. Moreover, we found classification images that reflected information within the blank regions of the original Mooney faces, suggesting that observers may fill in missing information using idiosyncratic internal information about faces.

Inside-the-body light delivery system using endovascular therapy-based light illumination technology.

BACKGROUND: Light-based therapies are promising for treating diseases including cancer, hereditary conditions, and protein-related disorders. However, systems, methods, and devices that deliver light deep inside the body are limited. This study aimed to develop an endovascular therapy-based light illumination technology (ET-BLIT), capable of providing deep light irradiation within the body. METHODS: The ET-BLIT system consists of a catheter with a single lumen as a guidewire and diffuser, with a transparent section at the distal end for thermocouple head attachment. The optical light diffuser alters the emission direction laterally, according to the optical fibre's nose-shape angle. If necessary, after delivering the catheter to the target position in the vessel, the diffuser is inserted into the catheter and placed in the transparent section in the direction of the target lesion. FINDINGS: ET-BLIT was tested in an animal model. The 690-nm near-infrared (NIR) light penetrated the walls of blood vessels to reach the liver and kidneys without causing temperature increase, vessel damage, or blood component alterations. NIR light transmittance from the diffuser to the detector within the organ or vessel was approximately 30% and 65% for the renal and hepatic arteries, respectively. INTERPRETATION: ET-BLIT can be potentially used in clinical photo-based medicine, as a far-out technology. ET-BLIT uses a familiar method that can access the whole body, as the basic procedure is comparable to that of endovascular therapy in terms of sequence and technique. Therefore, the use of the ET-BLIT system is promising for many light-based therapies that are currently in the research phase. FUNDING: Supported by Programme for Developing Next-generation Researchers (Japan Science and Technology Agency); JSPS KAKENHI (18K15923, 21K07217); JST-CREST (JPMJCR19H2); JST-FOREST-Souhatsu (JPMJFR2017); The Uehara Memorial Foundation; Yasuda Memorial Medical Foundation; Mochida Memorial Foundation for Medical and Pharmaceutical Research; Takeda Science Foundation; The Japan Health Foundation; Takahashi Industrial and Economic Research Foundation; AICHI Health Promotion Foundation; and Princess Takamatsu Cancer Research Fund.

Miniaturizing a Chip-Scale Spectrometer Using Local Strain Engineering and Total-Variation Regularized Reconstruction.

A wafer-thin chip-scale portable spectrometer suitable for wearable applications based on a reconstructive algorithm was demonstrated. A total of 16 spectral encoders that simultaneously functioned as photodetectors were monolithically integrated on a chip area of 0.16 mm2 by applying local strain engineering in compressively strained InGaN/GaN multiple quantum well heterostructures. The built-in GaN pn junction enabled a direct photocurrent measurement. A non-negative least-squares (NNLS) algorithm with total-variation regularization and a choice of a proper kernel function was shown to deliver a decent spectral reconstruction performance in the wavelength range of 400-645 nm. The accuracies of spectral peak positions and intensity ratios between peaks were found to be 0.97% and 10.4%, respectively. No external optics, such as collimation optics and apertures, were used, enabled by angle-insensitive light-harvesting structures, including an array of cone-shaped backreflectors fabricated on the underside of the sapphire substrate.

Light up: an intervention study of the effect of environmental dynamic lighting on sleep-wake rhythm, mood and behaviour in older adults with intellectual disabilities.

BACKGROUND: Evidence-based interventions to improve the sleep-wake rhythm, mood and behaviour in older adults with intellectual disabilities (ID) are limited. Increasing light exposure has been shown to be effective in improving the sleep-wake rhythm, mood, and behaviour in other populations. The current study investigates the effect of installing environmental dynamic lighting in common living rooms of care facilities on sleep-wake rhythm, mood, and behaviour in older adults with ID. METHODS: A non-randomised, non-concurrent, multiple baseline study was performed from October 2017 to May 2018. Fifty-four participants [mean (SD) age of 63.42 (8.6) years, 65% female] in six care facilities were included. All participants had three baseline measurements (Weeks 1, 5 and 9). Dynamic lighting was installed in Week 10, after which three intervention measurements took place (Weeks 12, 17 and 24). Sleep characteristics and the sleep-wake rhythm were assessed using actigraphy (GENEActiv). Mood was measured with the Anxiety, Depression and Mood Scale (ADAMS) and behaviour with the Aberrant Behaviour Checklist (ABC). RESULTS: Mixed-effect regression analysis showed a worsening of the primary outcome interdaily stability (P = 0.001). This could be attributed to one care facility, whereas interdaily stability did not change in the other care facilities (P = 0.74). Dynamic lighting led to earlier mid-sleep (P = 0.003) and sleep onset (P < .0001) and improved mood as indicated by lower scores on the ADAMS depression (-0.64 SD, P < 0.001) and social avoidance (-0.47 SD, P = 0.004) subscales. The prevalence of screening above cut-off for depression decreased from 23 to 9.8% (OR = .16, P = 0.003). For behaviour, a decrease was seen in hyperactivity (-0.43 SD, P < 0.001), lethargy (-0.35 SD, P = 0.008) and irritability (-0.33 SD, P < .001) as measured with the ABC. No adverse effects were reported. CONCLUSION: Installing dynamic lighting in common living areas for older adults with ID improved the mood and behaviour of the residents up to 14 weeks after placement. Integrated dynamic lighting is a promising, undemanding and potentially effective addition to improve mood and behaviour in care organisations for people with ID, but does not seem to do so by improving sleep or sleep-wake rhythms.

A new broadband near-infrared emitting Mg2Al4Si5O18:Cr3+ phosphor for night-vision imaging.

Phosphor-converted light-emitting diodes (pc-LEDs) have important applications in security surveillance and food testing. However, developing new broadband near-infrared phosphors remains an important issue. Herein, the high-temperature solid-state reaction method was applied to synthesize a new type of Cr3+ doped Mg2Al4Si5O18 broadband NIR phosphor which matches a blue LED chip. It exhibits a broadband near-infrared (NIR) phosphor emission with a focus of 856 nm and a full width at half maximum >200 nm after excitation at 453 nm. The optimum concentration of Cr3+ was established to contain 2 mol%. At 398 K, the luminescence intensity is 45.2% of that at 298 K. The power output of NIR pc-LEDs fabricated by incorporating a 450 nm chip and the Mg2Al4Si5O18:0.02 Cr3+ phosphor is 19.69 mW at 300 mA current. Finally, the developed NIR pc-LED shows significant potential for use in night-vision imaging.

Tunable White Light for Elders (TWLITE): A Protocol Demonstrating Feasibility and Acceptability for Deployment, Remote Data Collection, and Analysis of a Home-Based Lighting Intervention in Older Adults.

Sleep disturbances are common in older adults and may contribute to disease progression in certain populations (e.g., Alzheimer's disease). Light therapy is a simple and cost-effective intervention to improve sleep. Primary barriers to light therapy are: (1) poor acceptability of the use of devices, and (2) inflexibility of current devices to deliver beyond a fixed light spectrum and throughout the entirety of the day. However, dynamic, tunable lighting integrated into the native home lighting system can potentially overcome these limitations. Herein, we describe our protocol to implement a whole-home tunable lighting system installed throughout the homes of healthy older adults already enrolled in an existing study with embedded home assessment platforms (Oregon Center for Aging & Technology-ORCATECH). Within ORCATECH, continuous data on room location, activity, sleep, and general health parameters are collected at a minute-to-minute resolution over years of participation. This single-arm longitudinal protocol collected participants' light usage in addition to ORCATECH outcome measures over a several month period before and after light installation. The protocol was implemented with four subjects living in three ORCATECH homes. Technical/usability challenges and feasibility/acceptability outcomes were explored. The successful implementation of our protocol supports the feasibility of implementing and integrating tunable whole-home lighting systems into an automated home-based assessment platform for continuous data collection of outcome variables, including long-term sleep measures. Challenges and iterative approaches are discussed. This protocol will inform the implementation of future clinical intervention trials using light therapy in patients at risk for developing Alzheimer's disease and related conditions.

Effects of LED supplemental lighting on the growth and metabolomic profile of Taxus baccata cultivated in a smart greenhouse.

Light emitting diode (LED) lamps are increasingly being studied in cultivation of horticultural, ornamental and medicinal plants as means to increase yield, quality, stress resistance, and bioactive compounds content. Enhancing the production of metabolites for medicinal or pharmaceutical use by regulating LED intensity and spectra is a challenging subject, where promising results have been achieved. Nevertheless, some species have been poorly investigated, despite their interest as a source of medicinally active substances, with particular reference to LED effects at the plant cultivation level. This study evaluates the effects of supplementary top-light LED treatments on Taxus baccata, one of the main sources of taxane precursors. Blue, red and mixed red-and-blue spectra were tested at 100 µM m-2 s-1. Moreover, 50 and 150 µM m-2 s-1 intensities were tested for the mixed spectrum. All treatments were set for 14 hours a day and were tested against natural light as control treatment, in a controlled environment, from 19 August to 9 December 2019, this latter date representing 112 days after treatment (DAT) began. A smart monitoring and control system powered by environmental and proximal sensors was implemented to assure homogeneity of temperature, humidity, and base natural light for all the treatments. It resulted in negligible deviations from expected values and reliable exclusion of confusing factors. Biometric measurements and 1H-NMR based metabolomic analysis were performed to investigate growth and phytochemical profile throughout the trial. One-way ANOVA showed that supplemental LED lighting increased plant height and number of sprouts. Considering the mixed red-and-blue spectrum, plant height increased almost proportionally from control to 100 µM m-2 s-1 (+20% at 112 DAT), with no further increase at higher intensity. The number of sprouts was strongly enhanced by LED treatments only in the early phase (48.9 vs. 7.5 sprouts in the averaged 50, 100 and 150 µM m-2 s-1 vs. the control at 28 DAT), with no differences related to intensity in the very early stage, and more persisting effects (up to 56 DAT) for higher intensities. After the very early growth stages (28 DAT), plant vigor showed a modest although significant increase over time compared to the control, with no differences related to light intensity (0.81 vs. 0.74 of NDVI in the averaged 50, 100 and 150 µM m-2 s-1 vs. the control, across 56, 84 and 112 DAT). The different spectra tested at 100 µM m-2 s-1 showed no significant differences in growth parameters, except for a slight beneficial influence of blue (alone or with red) compared to only red for sprouting. According to the metabolomic analysis, treated plants at 28 DAT were characterized by the highest content of sucrose and aromatic compounds. Signals of a putative taxane were detected in the 1H NMR profiles of plants, which were compared to the spectrum of baccatin III standard. However, the intensity of these spectral signals was not affected by the treatment, while they increased only slightly during time. Light at 150 µM m-2 s-1 induced the strongest variation in the metabolome. Conversely, light composition did not induce significant differences in the metabolome.

Efficient removal of Imidacloprid and nutrients by algae-bacteria biofilm reactor (ABBR) in municipal wastewater: Performance, mechanisms and the importance of illumination.

Neonicotinoids, such as Imidacloprid (IMI), are frequently detected in water and wastewater, posing a threat on both the environment and the health of living things. In this work, a novel algae-bacteria biofilm reactor (ABBR) was constructed to remove IMI and conventional nutrients from municipal wastewater, aiming to explore the removal effect and advantage of ABBR. Results showed that ABBR achieved 74.9% removal of IMI under 80 µmol m-2·s-1 light, higher than photobioreactor (PBR) without biofilm (61.2%) or ABBR under 40 µmol m-2·s-1 light (48.4%) after 16 days of operation. Moreover, it also showed that ABBR allowed a marked improvement on the removal of total dissolved nitrogen (TDN), total dissolved phosphorus (TDP) and soluble chemical oxygen demand (sCOD). ABBR showed different IMI removal efficiencies and bacterial communities under different light conditions, indicating that light played an important role in driving ABBR. The merits of ABBR are including (i) ABBR showed rapid pollutant removal in a short time, (ii) in ABBR, stable consortiums were formed and chlorophyll content in effluent was very low, (iii) compared with PBR, degradation products in ABBR showed lower biological toxicity. Our study highlights the benefits of ABBR on IMI removing from municipal wastewater and provides an effective and environment-friendly engineering application potential of IMI removal.

Roles of illumination on distribution of phosphorus in Chlorella vulgaris under mixotrophic cultivation.

Phosphorus (P) is a non-substitutable resource and global reserves of phosphate rock are limited. In this study, phosphorus recovery by Chlorella vulgaris, and the effects of different light intensities (2000 Lux, 5000 Lux, 8000 Lux, 12,000 Lux) on the phosphorus distribution in the soluble microbial product (SMP), extracellular polymeric substance (EPS) and intracellular polymeric substance (IPS) were analyzed. The results showed that the 5000 Lux was the optimum light intensity for P uptake and transformation by Chlorella vulgaris under mixotrophic cultivation. At the light intensity of 5000 Lux, the P uptake rate was 100% after 32 days of cultivation, and the concentration of intracellular organic phosphorus (OP) was 5.77 mg P/L. Moreover, EPS was the main P pool when inorganic phosphorus (IP) was depleted in bulk solution. Phosphorus recovery by microalgae is an important solution to treat P-containing wastewater.

[Light therapy for depression].

Artificial light has been used as a treatment for depression since the 1980s. The indications have since broadened from seasonal depression to non-seasonal depression including bipolar, geriatric, and chronic depression. Light acts through retinohypothalamic connections from specialised retinal neurons to central nuclei involved in circadian and emotional regulation. This review illuminates the current strategies directed towards utilising natural daylight or electric lighting mimicking the dynamic spectrum and intensity of daylight to improve treatment in modern hospital settings.

Effects of dynamic bedroom lighting on measures of sleep and circadian rest-activity rhythm in inpatients with major depressive disorder.

Bright light therapy is an effective treatment option for seasonal and non-seasonal affective disorders. However up to now, no study has investigated effects of dynamic bedroom lighting in hospitalized patients with major depression. A bedroom lighting system, which automatically delivered artificial dawn and dusk and blue-depleted nighttime lighting (DD-N lighting) was installed in a psychiatric ward. Patients with moderate to severe depression were randomly assigned to stay in bedrooms with the new lighting or standard lighting system. Patients wore wrist actimeters during the first two treatment weeks. Additionally, hospitalization duration and daily psychotropic medication were retrieved from patients' medical charts. Data from thirty patients, recorded over a period of two weeks, were analyzed. Patients under DD-N lighting generally woke up earlier (+ 20 min), slept longer (week 1: + 11 min; week 2: + 27 min) and showed higher sleep efficiency (+ 2.4%) and shorter periods of nighttime awakenings (- 15 min). In the second treatment week, patients started sleep and the most active 10-h period earlier (- 33 min and - 64 min, respectively). This pilot study gives first evidence that depressed patients' sleep and circadian rest/activity system may benefit from bedroom lighting when starting inpatient treatment.

From dawn to dusk-mimicking natural daylight exposure improves circadian rhythm entrainment in patients with severe brain injury.

STUDY OBJECTIVES: While light therapy has proven effective in re-entraining circadian rhythms, the potential of such an intervention has not been evaluated systematically in post-comatose patients with disorders of consciousness (DOC), who often have strongly altered circadian rhythms. METHODS: We recorded skin temperature over 7-8 days in patients with DOC in each of two conditions: habitual light (HL), and dynamic daylight (DDL) condition. While patients were in a room with usual clinic lighting in the HL condition, they were in an otherwise comparable room with biodynamic lighting (i.e. higher illuminance and dynamic changes in spectral characteristics during the day) in the DDL condition. To detect rhythmicity in the patients' temperature data, we computed Lomb-Scargle periodograms and analyzed normalized power, and peak period. Furthermore, we computed interdaily stability and intradaily variability, which provide information about rhythm entrainment and fragmentation. RESULTS: We analyzed data from 17 patients with DOC (i.e. unresponsive wakefulness syndrome [n = 15] and minimally conscious state [n = 2]). The period length of the patients' temperature rhythms was closer to 24 h in the DDL as compared to the HL condition (median median deviation from 24 h: DDL = 0.52 h, HL = 3.62 h). Specifically, in 11/17 (65%) patients the period length was closer to 24 h in the DDL condition. Furthermore, the patients' rhythm was more pronounced, more stable, and less variable in the DDL condition. CONCLUSIONS: Our results indicate that DDL stimulation entrains and stabilizes circadian rhythms. This highlights the importance of adequate room lighting as an adjunct therapeutic approach for improving circadian rhythms in severely brain-injured patients. TRIAL REGISTRATION INFORMATION: German Clinical Trials Register (DRKS00016041); registration: 18.01.2019; recording start: 04.06.2019 https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00016041.