If you’re constantly changing your work hours or ??????? ???????? ?????frequently jet-setting between time zones, you may be more vulnerable to catching a virus than people with consistent work schedules or less erratic itineraries, a new study suggests.
The body’s internal clock works like a protective shield -- or an open door -- when it comes to viral infections, according to the study, which was published Monday in the journal Proceedings of the National Academy of Sciences.
Throw off your body clock, and viruses like the flu and common cold will have a greater opportunity to rush in, overtake your cells and spread throughout your body, the study's co-author Akhilesh Reddy, told Mashable.
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“When you disrupt the clockwork, then your clock is in no-man’s land,” Reddy, a clinical studies fellow at the University of Cambridge and a professor of experimental neurology, said during a phone interview.
“In that state, you’re more likely to get an infection.”
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The Cambridge study was performed on mice in a lab experiment, so its applicability to humans may be somewhat limited, but the new work does add to a growing body of research into circadian rhythms.
The daily rhythm represents the biochemical and physiological processes that rise and fall in your body over the course of 24-hours. These internally-driven cycles are what make us tired around our usual bedtime and help us wake up by the time the alarm rings. Body clocks also help regulate processes related to hormones, body temperatures and eating and digesting food.
While research has shownthat disrupting those cycles can lead to fatigue, poor motor control and irritability -- heightening the risk of injuries and harmful stress -- Monday's study offers new clues about the role of the circadian rhythm in helping us fight off infections.
Still, it doesn’t mean that people who wake up and go to sleep around the same time each day are an impenetrable fortress, warding off viruses.
A girl dons a face mask during flu season in Seoul, South Korea. Credit: ED JONES/AFP/Getty Images Reddy and Rachel Edgar, another author of the study, also found that our internal clocks may be weakest against viruses in the early morning and strongest in the evening.
“We used to assume viruses just came at you, regardless of the time of day,” Reddy said. “Our study found there’s particular times of day when the virus can infect more readily than at other times of day.”
For their study, Edgar and Reddy infected mice with a herpes virus at different times of the day, and compared the levels of infection and how far the virus spread. The mice lived in a controlled environment, with 12 hours of daylight and 12 hours of darkness.
The team found that virus replication was ten times greater in mice infected around sunrise than in mice infected 10 hours into the day, in the evening hours.
When researchers repeated the experiment in mice lacking a gene that controls the circadian rhythm, they found high levels of virus replication regardless of what time the mice were infected.
“This indicates that shift workers, who work some nights and rest some nights, and so have a disrupted body clock, will be more susceptible to viral diseases,” Edgar said in a press release.
Nurses care for babies in the premature natal intensive care unit at North Korea's Pyongyang Maternity Hospital. Credit: The Washington Post/Getty Images The U.S. National Institute for Occupational Safety and Health (NIOSH) has warned about the effects of disrupting the internal clocks of nurses, who often work sporadic 12-hour or 24-hour shifts with extended rest days, making it harder to settle into a natural rhythm.
“Research indicates that shift work and long work hours increase health and safety risks by disturbing sleep and circadian rhythms and reducing time for family and non-work responsibilities,” according to a training document that NIOSH researchers provided by email.
Reddy said he is now researching potential ways to replicate the body’s natural spike in virus protection that happens in the evening. He said that might include developing medications that patients could take in the morning period when defenses are naturally the weakest.
“If we can boost immune responses in the cells and in the whole body at that time of day, you can shield yourself better,” he said.