Studer, P., Brucker, J. M., Haag, C., Van Doren, J., Moll, G. H., Heinrich, H., et al. (2018). Effects of blue- and red-enriched light on attention and sleep in typically developing adolescents. Physiol Behav, 199, 11–19.
Abstract: Differential effects of blue- and red-enriched light on attention and sleep have been primarily described in adults. In our cross-over study in typically developing adolescents (11-17years old), we found attention enhancing effects of blue- compared to red-enriched light in the morning (high intensity of ca. 1000lx, short duration: <1h) in two of three attention tasks: e.g. better performance in math tests and reduced reaction time variability in a computerized attention test. In our pilot study, actigraphy measures of sleep indicated slight benefits for red- compared to blue-enriched light in the evening: tendencies toward a lower number of phases with movement activity after sleep onset in the complete sample and shorter sleep onset latency in a subgroup with later evening exposure times. These findings point to the relevance of light concepts regarding attention and sleep in typically developing adolescents. Such concepts should be developed and tested further in attention demanding contexts (at school) and for therapeutic purposes in adolescents with impaired attention or impaired circadian rhythms.
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Morelli, F., Mikula, P., Benedetti, Y., Bussière, R., & Tryjanowski, P. (2018). Cemeteries support avian diversity likewise urban parks in European cities: Assessing taxonomic, evolutionary and functional diversity. Urban Forestry & Urban Greening, 36, 90–99.
Abstract: The aim of this study was to explore different components of avian diversity in two types of urban green areas, parks and cemeteries, in four European countries in relation to environmental characteristics. We studied bird species richness, functional diversity and evolutionary distinctiveness in 79 parks and 90 cemeteries located in four European countries: the Czech Republic, France, Italy and Poland.
First, we found no significant differences between cemeteries and parks in bird diversity. However, in both parks and cemeteries, only: two community metrics were affected by different environmental characteristics, including local vegetation structure and presence of human-related structures. Species richness was positively correlated with tree coverage and site size, functional diversity was unrelated to any of the measured variables, while the mean evolutionary distinctiveness score was positively correlated with tree coverage and negatively associated with the coverage of flowerbeds and number of street lamps.
Our findings can be useful for urban planning: by increasing tree coverage and site size it is possible to increase both taxonomic richness and evolutionary uniqueness of bird communities. In both parks and cemeteries, the potential association between light pollution and bird species richness was negligible. We also identified some thresholds where bird diversity was higher. Bird species richness was maximized in parks/cemeteries larger than 1.4 ha, with grass coverage lower than 65%. The evolutionary uniqueness of bird communities was higher in areas with tree coverage higher than 45%. In conclusion, the findings of this study provide evidence that cemeteries work similarly than urban parks supporting avian diversity.
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Czaczkes, T. J., Bastidas-Urrutia, A. M., Ghislandi, P., & Tuni, C. (2018). Reduced light avoidance in spiders from populations in light-polluted urban environments. Naturwissenschaften, 105(11-12), 64.
Abstract: Increased urbanisation is leading to a rise in light pollution. Light pollution can disrupt the behaviour and physiology of animals resulting in increased mortality. However, animals may also benefit from artificial light sources, as these may aggregate prey or signal suitable environments. For example, spiders are commonly seen congregating around artificial light sources. Changes in selective pressures engendered by urban environments are driving changes in urban organisms, driving better adaptation to these environments. Here, we ask whether urban populations of the synanthropic spider Steatoda triangulosa show different responses to light compared to rural populations. Egg-sacs from urban and rural populations were collected and incubated in a common garden setting, and the emerging spiderlings tested for light preference. While rural spiderlings avoided light (37% built webs in the light), urban spiderlings were indifferent to it (49% built webs in the light). Reduced light avoidance may benefit spiders through increased prey capture, increased movement into suitable habitats, or due to a release from selection pressure from visually hunting predators which do not enter buildings.
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Zerbini, G., Kantermann, T., & Merrow, M. (2018). Strategies to decrease social jetlag: Reducing evening blue light advances sleep and melatonin. Eur J Neurosci, in press.
Abstract: The timing of sleep is under the control of the circadian clock, which uses light to entrain to the external light-dark cycle. A combination of genetic, physiological and environmental factors produces individual differences in chronotype (entrained phase as manifest in sleep timing). A mismatch between circadian and societal (e.g., work) clocks leads to a condition called social jetlag, which is characterized by changing sleep times over work and free days and accumulation of sleep debt. Social jetlag, which is prevalent in late chronotypes, has been related to several health issues. One way to reduce social jetlag would be to advance the circadian clock via modifications of the light environment. We thus performed two intervention field studies to describe methods for decreasing social jetlag. One study decreased evening light exposure (via blue-light-blocking glasses) and the other used increased morning light (via the use of curtains). We measured behaviour as well as melatonin; the latter in order to validate that behaviour was consistent with this neuroendocrinological phase marker of the circadian clock. We found that a decrease in evening blue light exposure led to an advance in melatonin and sleep onset on workdays. Increased morning light exposure advanced neither melatonin secretion nor sleep timing. Neither protocol led to a significant change in social jetlag. Despite this, our findings show that controlling light exposure at home can be effective in advancing melatonin secretion and sleep, thereby helping late chronotypes to better cope with early social schedules.
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Lowden, A., Lemos, N., Gonçalves, B., Öztürk, G., Louzada, F., Pedrazzoli, M., et al. (2018). Delayed Sleep in Winter Related to Natural Daylight Exposure among Arctic Day Workers. Clocks & Sleep, 1(1), 105–116.
Abstract: Natural daylight exposures in arctic regions vary substantially across seasons. Negative consequences have been observed in self-reports of sleep and daytime functions during the winter but have rarely been studied in detail. The focus of the present study set out to investigate sleep seasonality among indoor workers using objective and subjective measures. Sleep seasonality among daytime office workers (n = 32) in Kiruna (Sweden, 67.86° N, 20.23° E) was studied by comparing the same group of workers in a winter and summer week, including work and days off at the weekend, using actigraphs (motion loggers) and subjective ratings of alertness and mood. Actigraph analyses showed delayed sleep onset of 39 min in winter compared to the corresponding summer week (p < 0.0001) and shorter weekly sleep duration by 12 min (p = 0.0154). A delay of mid-sleep was present in winter at workdays (25 min, p < 0.0001) and more strongly delayed during days off (46 min, p < 0.0001). Sleepiness levels were higher in winter compared to summer (p < 0.05). Increased morning light exposure was associated with earlier mid-sleep (p < 0.001), while increased evening light exposure was associated with delay (p < 0.01). This study confirms earlier work that suggests that lack of natural daylight delays the sleep/wake cycle in a group of indoor workers, despite having access to electric lighting. Photic stimuli resulted in a general advanced sleep/wake rhythm during summer and increased alertness levels.
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