...The finding adds to a growing body of research showing that a healthy pattern of light and dark, sleeping and waking, is essential to keep the immune system in balance, Hooper says. She notes that inflammation is the basis of many chronic disorders, such as heart disease, asthma, chronic pain, and many things ending in "-itis," like bursitis and dermatitis. Inflammatory conditions are more prevalent in developed countries, where people's circadian rhythms are chronically disrupted. Even people who don't work shifts or cross time zones still wake and sleep out of sync with light and darkness, Hooper says. "We all have screwed up light cycles. We stay up late, keep the lights on, look at our lit-up iPhones at 2 a.m."
http://www.huffingtonpost.com/2013/11/08/sleep-immune-system-body-clock_n_4235943.html