Sleep & Circadian Rhythm


“Timing is everything” may be an old cliché, but for Northwestern Medicine scientists it’s also a reflection of emerging discoveries in physiology: that the body’s circadian clocks are in fact critical to driving a host of behaviors, processes and pathways — including those associated with several diseases and pathologies. Northwestern Medicine investigators are exploring the many facets of sleep and circadian rhythm to make broad new discoveries in human health.

Media Coverage

Associated Press

Animal research and smaller studies in humans have linked prolonged light exposure with weight gain. Exactly how is uncertain but scientists think disruption in release of hormones related to sleep and appetite may be involved. Dr. Phyllis Zee, an expert in sleep and circadian rhythm disorders at Chicago’s Northwestern University, said the study is important because it highlights a behavior that can be easily changed to reduce the risk of gaining weight. “Properly timed light should be considered as part of a healthy life style,” she said, along with exercise and good nutrition.
The Washington Post

The study by researchers at Northwestern University found that fruit flies carrying a gene for Huntington’s disease appeared to receive a protective boost against the brain-damaging illness when researchers changed the insects’ sleep cycles in a way similar to jet lag. The team also found that silencing a circadian clock-controlled gene produced a similar benefit. “It seems counterintuitive, but we showed that a little bit of stress is good,” Ravi Allada, a physician who heads the neurobiology department at the university’s Weinberg College of Arts and Sciences and Pathology, said in a statement. “We subtly manipulated the circadian clock, and that stress appears to be neuroprotective.”

Based on the observational nature of the study, the researchers were unable to show causality, meaning it is unclear whether the sleep disturbances caused the mental health problems or vice versa. "It's a cross-sectional study, so we can't say anything about cause and effect or what came first, the mood disorder or the circadian disruption," said Kristen Knutson, associate professor of neurology at Northwestern's Feinberg School of Medicine, who was not involved in the study.

“The main role of circadian rhythm is to anticipate what you’re going to be doing at certain points of the day,” says Kristen Knutson, PhD, associate professor of neurology and sleep medicine at Northwestern University Feinberg School of Medicine. “When there’s a mismatch and you’re not doing what your biology expects at a certain time, your body may not handle it as well; it may not process food or glucose as rapidly, for example.”