It is 92,960,000 miles away and the most powerful source of energy and life on Earth. For more than 4.5 billion years, until the invention of the incandescent light bulb in the 1800s, the sun was our only source of light, and human behavior revolved around the light-dark pattern it set. Manufactured light altered human dependence on the day-night cycles of the sun and, perhaps an unintended consequence, affected circadian sleep-wake cycles.
Research in the 1970s showed that the circadian rhythm not only regulates sleep-wake cycles but also has a molecular mechanism that influences individual cells and organ systems. Several decades later, there is substantial biomedical research that correlates disrupted circadian rhythms with health problems such as sleep disorders, metabolic syndrome and obesity, diabetes, and cardiovascular and other clinical diseases. Research has also shown that patients in the ICU suffer from sleep deprivation and disturbances, in addition to critical illnesses,...
