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Dynamic lighting is a potentially promising solution to meet the individual's chronobiologic and psychological needs at specific times of day or for specific activities. Yet, few studies have investigated the impact of dynamic lighting patterns on daytime functioning and nocturnal sleep, and the optimal dynamic lighting pattern remains largely unknown. The current study assessed the effects of a daylong dynamic lighting (DL) pattern with modulations in intensity and spectrum vs. static office lighting (SL) on markers of well-being, cognitive performance, visual experiences, and sleep in a simulated office environment. Twenty-one subjects participated in the 48-h balanced crossover laboratory study. The findings revealed time-of-day and experimental-day dependent benefits of the DL vs. SL pattern on daytime vitality, sleepiness, state self-control, mood, performance on a sustained attention task and subsequent subjective sleep quality. Complementing earlier research outcomes reported in the literature, the current study suggests that a dynamic lighting approach could be a practical strategy to support office workers' daytime well-being and nocturnal sleep. Yet, the results revealed no consistent pattern across assessments nor across the different types of metrics at a specific assessment, thus additional research regarding the optimization of lighting parameters and pattern is needed.

In this field study, we tested the effects of dynamic light scenarios and personal illuminance on visual experience, sleepiness, cognitive performance and sleep in an operational office. Two dynamic light scenarios, different in timing but with equal luminous exposure, were tested against a reference scenario in a counterbalanced crossover design. Frequent assessments of visual experience, alertness, performance and sleep showed that in both dynamic light scenarios visual comfort was slightly lower compared to the constant scenario. Additionally, sleepiness was lowest in the scenario with the brighter light timed around noon, whereas task performance and actual sleep were not significantly affected. The measured personal illuminance did not predict sleepiness and performance, yet variation and timing of these illuminances did positively relate to sleep onset and duration. When studying or implementing light scenarios aiming to deliver integrative lighting, the spatial and behavioral context should be considered as well.

Throughout the day, we are exposed to light that varies drastically over time. Correct quantification of the light is important when predicting sleep and subjective alertness in the field, yet doing so, is a complex challenge. In the current manuscript, we explore the feasibility of a novel, practical method to quantify light exposure, based on the data collected in two field studies (in late spring and winter). Data include indicators of sleep, subjective alertness, and personal luminous exposure. We explored Time above Threshold (TaT) and Mean Light Timing above Threshold (MLiT) metrics, as well as their interaction, to quantify intensity, timing, and duration of light in testing not only circadian but also acute alerting effects of light in the field during office hours. For both measures, sensitivity analyses were performed across a large range of illuminance thresholds. The aim was to explore if these analyses would render indications for (a range of) effective thresholds, and to test if this alternative method of quantifying light would outperform simple averaging over specific time intervals. Despite the relatively small data set, the current approach seems promising particularly for predicting sleep: models performed slightly better than traditional models using average light exposure as predictor. More importantly, this method takes into account intensity, duration and timing, providing more detailed insights in the relation between luminous exposure and different outcome measures. We encourage this method to be explored further with larger data sets, discuss shortcomings of the current analyses and suggest potential directions for improvement.