New research suggests that viral infections are more dangerous to those with varied body clocks
Men and women who work changing shift hours are more likely to suffer from colds and flu, according to new research published by a University of Cambridge study. The scientists found that fluctuations to the body clock made people more likely to succumb to an illness, while those with a regular sleeping pattern made it harder for viruses to replicate and spread between cells.
The study, published in the Proceedings of the National Academy of Sciences, will offer support to the anecdotal belief that shift workers, whose circadian rhythm is interrupted by having to go against the natural impetus to rest during the night, are more prone to health troubles, such as infections and chronic diseases.
Viruses that make their way beyond the first defences of the human body hijack healthy cells and use their cellular systems to replicate and reproduce throughout the body. The ability of the body’s cells to fend off infection has been seen to vary throughout the day, largely associated with the ebb and flow of the circadian rhythm, the name given to the body process that governs sleeping patterns, regulates temperature, controls the immune system, as well as the release of hormones.
In this new study, mice infected with herpes at different points during the day were observed to see how well the virus managed to spread. The scientists strictly regulated the mice’s living conditions, exposing them to 12 hours of light and the same period of darkness.
The researchers noted that the mice infected at the beginning of the day – tantamount to sunrise, when nocturnal mice are typically beginning to rest – suffered from infections 10 times greater than those exposed 10 hours into the day, when mice are beginning to wake up. When the Cambridge team replicated the experience in mice without the Bmal1 gene, which governs the body clock, they discovered the same high levels of viral replication no matter what time of day the mice were exposed.
“The time of day of infection can have a major influence on how susceptible we are to the disease, or at least on the viral replication, meaning that infection at the wrong time of day could cause a much more severe acute infection,” said Professor Akhilesh Reddy, the study’s senior author. “This is consistent with recent studies, which have shown that the time of day that the influenza vaccine is administered can influence how effectively it works.”
Dr Rachel Edgar added: “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. If so, then they could be prime candidates for receiving the annual flu vaccines.”
The research also suggests that the genes governing the circadian rhythm also react to seasonal change, becoming less active in the winter months, just as viral diseases like influenza are at their annual peak.