BY JANET JANKOWIAK, MD and ERIC REINES, MD
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Over the past 3.7 billion years, life on earth has evolved, dependent on the daily cycles of the sun. Even human clock genes in our various cells are programmed to respond to this approximately 24-hour cycle, our circadian rhythm. But over the past 200
years, the proliferation of artificial light at night (ALAN) has been powerful enough to interfere with fine-tuned adaptations to these light/dark cycles made over eons by various living organisms. While ALAN has allowed humans to be productive
far into the dark hours and essentially 24/7, it has also brought unintended health consequences. Physician organizations, including the American Medical Association (AMA) and the Massachusetts Medical Society (MMS), are taking notice and proposing
solutions.
ALAN has dramatically disturbed our circadian rhythms, most notably our sleep cycles. In turn, many people are chronically sleep-deprived, which contributes to mood disorders and reduced cognitive efficiency and learning. Disrupted circadian rhythms,
associated with ALAN, have been strongly linked to impaired metabolic functions, obesity, and various types of cancer, especially those that are endocrine-related.
Hazards Increase with Age and Vary with Light Spectrums
The impact of ALAN depends both on timing and the spectrum of light. Blue light (color temperature 4,000 to 6,000K) has the most impact because it suppresses melatonin secretion by the pineal gland. Without proper timing of melatonin (nicknamed the Dracula
hormone because it peaks at night and helps to induce sleep), our sleep-wake cycle may be thrown off. Our various electronic screens are particularly notable for blue light emission, although there are features to reduce this emission on some
phones and computers. Limiting exposure late at night is particularly important for a good night’s sleep; ideally all screens should be turned off and stored overnight in another room.
Blue light is also emitted by many streetlights and vehicle headlights, which pose other public health issues. As we mature, older eyes become more sensitive to glare. Irregularities in the corneal surface due to decreased tear production, as well as
decreased transparency of the lens and cornea, cause light to scatter and contribute to glare. With age, pupils become smaller (senile miosis) and the number of retinal rods decreases, making adaptation to dark more difficult and recovery from
glare slower. Consequently, night driving becomes more hazardous with age.
The MMS and the AMA are Taking Steps to Decrease Light Pollution
What can we do to decrease light pollution and improve public health while also saving energy? Light Emitting Diode (LED) lighting uses considerably less energy than older incandescent and fluorescent lighting. Further improvement requires minimizing
and controlling blue-rich environmental lighting to diminish glare yet retain efficiency. For that reason, the AMA encourages the
use of 3,000K or less lighting for outdoor public installations, such as streetlights, roadways, businesses, and homes, as well as for vehicle headlights. Because LED lights originally tended to be unidirectional (i.e., an intense point source
of narrow bandwidth light) they required better shielding, such as with lamp shades in the home. Newer versions of LED lights are less “harsh” as they emit a warm, amber, diffuse glow (color temperature 2,200K).
In the interest of promoting improved road and nighttime safety, the MMS Committee on Geriatric Medicine wrote and submitted a report on Glare and Older Drivers to the MMS House of Delegates (HOD). It was adopted, with amendments, at the HOD Interim Meeting
in December 2022. The report calls for the MMS to advocate to the state legislature for the use of 2,700K or lower color temperature light emitting diodes, as well as proper shielding for all outdoor applications such as roadways. The MMS Committee
on Geriatric Medicine and Committee on Environmental and Occupational Health will continue to monitor research on the topic and share relevant information with MMS members.
Janet Jankowiak, MD, a geriatric and behavioral neurologist, and Eric Reines, MD, an internist and geriatrician, are both members and former chairs of the MMS Committee on Geriatric Medicine.
