Shift workers more prone to infections due to body clock changes

Feel a cold coming on in the morning?

Shift workers are more at risk of viral infections because of the effect on their body clocks, according to new research.

Scientists at Cambridge University used mice to learn that shift workers are more in danger of getting an infection due to the disturbance to their body clocks.

They found that virus replication in those mice infected at the very start of the day – equivalent to sunrise when these nocturnal animals start their resting phase – was ten times greater than in mice infected ten hours into the day.

Professor Akhilesh Reddy, the study’s senior author, said: “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.

“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.

“Each cell in the body has a biological clock that allows them to keep track of time and anticipate daily changes in our environment.

“Our results suggest that the clock in every cell determines how successfully a virus replicates.

“When we disrupted the body clock in either cells or mice, we found that the timing of infection no longer mattered – viral replication was always high.

“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.

“Given that our body clocks appear to play a role in defending us from invading pathogens, their molecular machinery may offer a new, universal drug target to help fight infection.”

Researchers at the Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, compared normal ‘wild type’ mice infected with herpes virus at different times of the day, measuring levels of virus infection and spread.

The mice lived in a controlled environment where 12 hours were in daylight and 12 hours were dark.

When a virus enters the body, it hijacks the machinery and resources in cells to help it replicate and spread throughout the body.

However, the resources on offer fluctuate throughout the day, partly in response to our circadian rhythms – in effect, the body clock.

Circadian rhythms control many aspects of our physiology and bodily functions from our sleep patterns to body temperature, and from our immune systems to the release of hormones.

The research was mostly funded by the Wellcome Trust and the European Research Council.