Scientists have long recognized that human metabolism moves through cycles that are synchronized with natural 24-hour “circadian rhythms.” Anything that interrupts those rhythms, including exposure to extended periods of bright light or absences of light, can affect a person’s health and psychological condition. For example, people who live in far northern or southern climates and who have little exposure to sunlight during winter months can suffer from “seasonal affective disorder”, which is a form of clinical depression. Recognizing this, lighting designers and engineers are now paying greater attention to how their products affect the health of individuals who are exposed to those lights.
A person’s heart health, in particular, can be adversely affected by excess exposure to artificial lighting. As a day progresses and the sun sets, a person’s body will produce greater quantities of the hormone melatonin, which helps a person to relax and sleep during dark evening hours. When a person is exposed to too much sunlight or excess amounts of artificial light, melatonin production is impaired and that person’s sleep cycles are interrupted. Proper melatonin levels are also associated with lower blood pressure and platelet production, both of which are directly connected with heart health. Thus, an individual who experiences excess exposure to artificial light can suffer from hypertension and narrowing of arteries due to excess circulatory system plaque.
Certain harsh, or high CCT-temperature light sources, can also affect a person’s vision and create excessive eye strain, leading to headaches and other discomforts. Lighting specialists suggest controlling, or at least moderating these health effects by focusing on lighting intensity and spectrum, as well as the timing and duration of the light that a person may be exposed to during a typical day. Light intensity can be higher during morning and afternoon hours to stimulate people and reduce any early-morning or afternoon senses of fatigue. As a day progresses, intensity levels should be reduced to ease the transition into a restful evening.
The color spectrum of artificial light will also have a great affect on a person’s health. Natural light, which has a color rendering index (“CRI”) of 100, is perceived to be ideal for many applications. Newer LED lighting systems are better able to replicate a natural CRI in almost every environment. LED systems also allow light spectrums to be changed during a day to better coordinate with CCT adjustments, all of which facilitates a healthier artificial light environment.
Beyond intensity and spectrum, the timing and duration of a person’s exposure to artificial light may be more difficult to control. Awareness of these issues is a starting point for controlling them. Research is currently being conducted to determine optimal levels of light and how those levels can be adjusted and controlled to minimize health effects. Until then, building operators can take steps to reduce problems that artificial lighting can cause, including using diffusers on light fixtures to reduce harsh glare, and adjusting artificial lighting levels during evening hours to reduce impairment of melatonin production.