New approach sheds light on ways Circadian disruption affects hu...( Troy N.Y. Growing evidence indicate...),Health

Troy, N.Y. Growing evidence indicates that exposure to irregular patterns of light and darkness can cause the human circadian system to fall out of synchrony with the 24-hour solar day, negatively affecting human health but scientists have been unable to effectively study the relationship between circadian disruptions and human maladies.

A study by researchers in Rensselaer Polytechnic Institute's Lighting Research Center (LRC) provides a new framework for studying the effects of circadian disruption on breast cancer, obesity, sleep disorders, and other health problems.

Light and dark patterns are the major synchronizer of circadian rhythms the biological cycles that repeat approximately every 24 hours to the solar day. Inadequate or irregular light exposure can cause circadian rhythm disruptions that are believed to manifest into a variety of health ailments. However, ecological studies to measure human light exposure are virtually nonexistent, making it difficult to determine if, in fact, light-induced circadian disruption directly affects human health.

LRC researchers have created a small, head-mounted device to measure an individual's daily rest and activity patterns, as well as exposure to circadian light short-wavelength light, particularly natural light from the blue sky, that stimulates the circadian system. The device, called the Daysimeter, was sent to 43 female nurses across the country to measure their daily exposure to circadian light, according to Mark Rea, director of the LRC and principal investigator on the project.

The Daysimeter was worn for seven days by both day-shift and rotating shift nurses and then returned to the LRC for analysis. Simultaneously, Rea and his colleagues studied the effect of irregular light exposure to the circadian system of 40 rats, in order to determine if the relationship between circadian disruption and health outcomes could be uncovered using rodent models.