by 
Volume 16, Number 9
Life without artificial light is very difficult to imagine, as our quality of life has been enhanced in many ways with this important invention. It is unlikely that Thomas Edison gave any consideration to possible adverse health effects in his pursuit of the invention of the incandescent bulb. However, most things in life are not absolutely all good or all bad, and artificial light fits that description.
Artificial light at night (ALAN) has received research attention over the past few decades, with respect to how it can affect circadian patterns and sleep, and what associations there may be to health. Of course, the availability of artificial light contributes to persons staying up later and thereby getting less sleep. Exposure to ALAN, both indoor and outdoor, also has been found to impact the frequency of arousals during sleep, the amount of shallow sleep, and overall sleep quality. Furthermore, exposure to ALAN has been associated with increased risk of mental health problems, obesity, and some cancers.
Even exposure to dim ALAN appears to be problematic, particularly exposure to shortwave light (i.e., blue light). It is estimated at least 90% of American adults use electronics within an hour of bedtime, at least a few nights per week. Compared to persons reading a printed book prior to sleep, those using light-emitting e-readers have been found to take longer before falling asleep, have reduced melatonin secretion, and experience decreased alertness the following morning.
Studies of outdoor ALAN have made use of satellite data so they are not dependent on the self-report of research participants. Of note, greater exposure to outdoor ALAN is higher in lower socioeconomic neighborhoods. Given ALAN’s association with obesity and other health problems, outdoor ALAN exposure represents one of the many contributors to social and economic health disparities.
Sleep is certainly one of the most important but often underappreciated heath behaviors. Taking steps to improve sleep quality and quantity are meaningful. Based upon the research data regarding the impact of ALAN, limiting exposure to ALAN (especially short-wave blue light) prior to bedtime and during sleep is one such step. There does not appear to be existing research on the impact of blackout curtains/shades or sleep masks, but they may be worth considering for those who cannot otherwise control exposure to indoor or outdoor ALAN.
by