## 4 Results
### Sleep-Related Health Outcomes  
Ten of the reviewed articles specifically investigated sleep-related health outcomes, focusing on sleep quality, sleep-wake patterns, and duration (refer to Table 4). Natural light cycles promote alertness and wakefulness by synchronizing individuals' circadian rhythms to the daily environment [2; 67; 32]. On the other hand, as a result of artificial light exposure at night (ALAN), circadian rhythms can be disrupted, which can affect sleep quality and make it more difficult to fall asleep [32; 60]. However, the results across studies have not consistently supported this viewpoint regarding ALAN. In one study conducted in institutionalized elderly patients with dementia, activity and sleep were investigated using a wrist activity monitor (Actilume) [32]. Each patient received one of four treatments at random: evening bright light (2500 lux from 17:30 to 19:30), morning bright light (500 lux from 9:30 to 11:30), evening dim red light (red light less than 50 lux between 17:30 and 19:30), or daytime sleep restriction (DSR). Interestingly, the effect of increasing light exposure in the mornings or evenings on sleep or alertness during the day was inconclusive [32]. In another study of a younger population of hospitalized inpatients, sleep-wake activity patterns were also assessed using wrist actigraphs/light meters. There were chronic light exposure levels that did not adequately synchronize circadian rhythms with a mean daytime light intensity of 104.80 lux. This low light level caused sleep disturbances as well as circadian disruptions [60]. In medical inpatients, there was no synchronization of light exposure with sleep-wake patterns, suggesting a need for further investigation of how manipulating light exposure can be beneficial [60]. In one study, simulated natural lighting systems were used in intensive care units (ICUs) as part of an intervention research project to support patients' circadian rhythms compared with traditional lighting systems [56]. Although interviews with patients who had experienced sleep disorders revealed their satisfaction with the dynamic lighting environment, this study only used self-reported subjective measures from the patients and did not provide clear objective evidence that the light intervention influenced factors such as circadian rhythm maintenance and subsequent recovery [56]. In a similar study, dynamic lighting \begin{table}
\begin{tabular}{c c c} \hline \hline \# & **Study Types** & **Ref.** \\ \hline
**1** & **Experimental Studies** & \\  & \(\bullet\) Randomized controlled trial & [25; 32; 55] \\  & \(\bullet\) Intervention study & [26; 56] \\  & \(\bullet\) Controlled clinical trial & [57] \\  & \(\bullet\) Experimental measurements & [57; 59] \\
**2** & **Quasi-Experimental Study** & \\  & \(\bullet\) Clinical test bed & [57] \\
**3** & **Observational Study** & \\  & \(\bullet\) Observation & [6; 57; 58; 62; 63; 64; 65; 66] \\  & \(\bullet\) Field survey & [26; 32; 59; 63] \\  & \(\bullet\) Correlational study or non-experimental study & [60] \\  & \(\bullet\) Retrospective cohort study & [27; 61] \\
**4** & **Qualitative Study/Case Study** & \\  & \(\bullet\) Case study & [62; 65] \\  & \(\bullet\) Pilot study & [23; 58; 64] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary of studies with the interventions and human participant studies. interventions were evaluated on sleep outcomes in inpatients. By providing low nocturnal light exposure, and 2 h of bright light (1750 lux) during the day, the lighting system with a dynamic 24 h light/dark cycle can improve inpatient sleep compared to traditional lighting systems [25]. However, additional clinical research is needed to identify the effective lighting design and strategy to improve health outcomes and status in healthcare settings [25]. Conversely, no significant improvement was reported in sleep quality, mood, or well-being among psychiatric inpatients in response to a dynamic circadian lighting system [55].