We have all heard those grandma stories about getting sick when you go out in the cold. Of course, we never believed them, but studies today show there may be some relation between time and infections.
Tests done on mice have shown that when they are infected by a virus in the morning, it spreads faster than when they are infected with the same virus later during the same day. The way that viruses make you sick is by reproducing themselves in adjacent cells until they overwhelm the body with the virus.
Biological clock experiments
The study published on August 15 in the Proceedings of the National Academy of Sciences journal says that this must be due to the mice’s biological clock or circadian rhythm. According to the study, the bio clock not only regulates sleep and wakes us up, but it also has to do with our immune system. Since the study was done on mice, it is unclear if the same thing happens to human beings. The study also says that the immune system repairs itself during the rest period of the bio clock so it is possible that it falls prey to disease faster during this time.
The experiment was done using the herpes virus, and its replication was measured constantly. The mice were held in a natural atmosphere with twelve hours of light and twelve hours of darkness. The results showed that the virus multiplied ten times more when the virus was injected at sunrise than when it was injected ten hours later (mice are night animals so they start their resting period at sunrise).
The experiment was repeated with mice which did not have a specific gene linked to the bio clock, and the virus multiplied in them at all times of the day at the same speed. There was no difference at what time during the day they were infected.
Another experiment was done with cell cultures from mice in the laboratory. With these, they found that not only did the herpes virus spread faster, but that it also altered the bio clock mechanisms making the cells an easier prey to infection and disease. Studies done with malaria have also shown that the parasite that causes it times its multiplication patterns with the cells’ circadian rhythm, invading them faster than they would when the bio clock is not active.
What does this mean for you?
Akhilesh Reddy, the neuroscientist from the University of Cambridge who did the research, says that the time of day in which we are infected by virus has a great influence on our susceptibility to that infection or disease. This means that the time of day in which we are infected will influence the speed with which the virus spreads and therefore how sick we will become.
This could explain why some people, like people who work shifts, may be affected more by viruses and infections than those who work regular daily hours.