A study entitled Sleep Mathematics conducted by the Polytechnic Institute and Icahn School of Medicine in New York examining the effects of reduced light exposure during the day during the Covid-19 pandemic due to the transition from a work (school) to home environment confirmed that the more light a person is exposed to during the day, whether at home, work or outdoors, the better their subjective perception of sleep quality. The research findings highlight the importance of choosing light sources that are in harmony with circadian rhythms thus benefiting the user’s sleep, health and well-being when designing lighting in homes, offices and schools.
Higher light exposure during the day improves sleep quality
The study confirms that exposure to indoor light or time spent outdoors during the day is highly related to respondents’ subjectively perceived sleep quality. The results show that spending 1-2 hours a day outdoors or in a room with very high luminance (or melanopic equivalent daylight luminance, mEDI, which indicates the biological effectiveness of lighting) improves the quality of sleep at night and reduces the likelihood of sleep disturbances.
Higher light levels during the day improve mood and reduce stress
The authors found that prolonged exposure to daylight, whether indoors or outdoors, was associated with better mental and emotional outcomes for study participants during the COVID-19 pandemic.
Participants in the group exposed to ‘very bright’ indoor light had higher positive affect (feelings of pleasure, joy and happiness) compared to participants in the ‘dim’ and ‘neutral’ light groups. At the same time, participants in the ‘dim’ indoor light group had significantly higher stress and depression scores compared to participants in the other brighter light groups.
Building on their own research and the studies cited above, the authors submit recommendations for improving sleep quality and increasing the sense of well-being. They recommend spending 1 to 2 hours a day outdoors, ideally in the morning after waking up to support the natural circadian rhythm. For people working from home, it is essential to maximise natural daylight indoors and optimise the distribution of light in the room. In the morning and during the day, the solution when staying indoors is full-spectrum lighting with maximum circadian effect or the maximum melanopic EDI lux number. Evening lighting should be warm, dimmed and placed low, and electronic displays should be turned off at least 1-2 hours before bedtime to minimise the sleep cycle disruption.
