This research stemmed from the question of how lighting situations in office buildings can affect sleep and mood. They were curious as to how office lighting contributed to a person’s circadian light- dark and activity rest patterns. They hypothesized that there would need to be an increase in circadian light exposures in buildings.
Before beginning their study they conducted research on circadian rhythms. They found that the circadian rhythm requires a certain level and wavelength of light to become activated; daylight perfectly matches the criteria it needs. They also note that lighting in office buildings do not always match daylight due to several factors like energy codes and budgets.
The research continues on to discuss how this circadian clock controls many aspects of our body. The research notes that it “regulates body temperature, melatonin production, sleep, activity-rest behavior, alertness, mood and performance” (Figueiro & Rea, 1). Thus they wanted to test the effects on sleep and mood in office settings with and without windows. They further developed the study by studying the same subjects during two seasons, summer and winter. Their goals were to take note of offices with natural lighting as compared to offices with artificial lighting.
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Additionally they were to collect self-reports of sleep and mood from the subjects. Their research was a experiment, in which participants wore a Daysimeter, a light measuring device, and were asked to keep a detailed sleep log. This was conducted for 7 days in the winter and 7 days in the summer by the same participants. From this experiment the data from the Daysimeter was analyzed to determine the total light exposure during waking and working hours. They also got data values for the regularity of daily activity and fragmentation of those activities. They used the sleep logs and the Daysimeter data to calculate several aspects of sleep including, sleep time, wake time, sleep efficiency and sleep latency.
The results showcased that sleep was poorer in the winter alongside higher depression scores. These scores also had a correlation value with low stimulus of the circadian.
However none of the results posed were statistically significant. Although these results did not give them a definitive answer to their overall question it gave more insight. They believe the results were not statistically significant due to the small sample size. However their research does show that more light during the daytime did help participants have a better quality of sleep the following night. However this study still has work that remains.
