"It is estimated that a “white” LED lamp is at least 5 times more powerful in influencing circadian physiology than a high pressure sodium light
based on melatonin suppression. Recent large surveys found that brighter residential nighttime
lighting is associated with reduced sleep time, dissatisfaction with sleep quality, nighttime
awakenings, excessive sleepiness, impaired daytime functioning, and obesity. Thus, white LED
street lighting patterns also could contribute to the risk of chronic disease in the populations of
cities in which they have been installed. Measurements at street level from white LED street lamps
are needed to more accurately assess the potential circadian impact of evening/nighttime exposure
to these lights."
http://darksky.org/wp-content/uploads/bsk-pdf-manager/AMA_Re...
A representative section.
"It is estimated that a “white” LED lamp is at least 5 times more powerful in influencing circadian physiology than a high pressure sodium light based on melatonin suppression. Recent large surveys found that brighter residential nighttime lighting is associated with reduced sleep time, dissatisfaction with sleep quality, nighttime awakenings, excessive sleepiness, impaired daytime functioning, and obesity. Thus, white LED street lighting patterns also could contribute to the risk of chronic disease in the populations of cities in which they have been installed. Measurements at street level from white LED street lamps are needed to more accurately assess the potential circadian impact of evening/nighttime exposure to these lights."