Hospital clinicians have a new tool in their arsenal to reduce fatigue and depression: the light switch. Just as the seasonal darkness of winter can lead to depression in some people, there are signs that hospital inpatients feel better mentally and physically if exposed to minimal levels of light each day.

A study of otherwise mentally healthy patients concluded that they were not getting enough light during the day to allow for regular sleep patterns to develop — known as circadian entrainment — which likely disrupts their sleep patterns and their mood. Sleep patterns were fragmented, and patients averaged only four hours in a 24-hour period.

"They're consistently, however long their stay, exposed to too little light to have any effect on their circadian entrainment," says Esther Bernhofer, R.N., lead author of the study, published recently in the Journal of Advanced Nursing, and nurse researcher in the Cleveland Clinic Nursing Institute's Office of Research and Innovation. "It's like permanent jet lag."

Because there are plenty of other reasons that a patient might not sleep well, additional research is needed to establish that the low light is affecting patients, she says. But Bernhofer notes that relying on the naked eye to determine whether light in a patient's room is adequate would be a mistake. Light meters are needed to measure the amount of light. "The eye is not very good at determining that," she says.