Timing Your Health
As the Romans wrote, time rules life – especially our biological inner life. Body clocks influence or directly control large segments of human physiology and performance. So recent work by researchers at Cambridge’s MRC Research Unit, demonstrating that viruses as varied as herpes and influenza A infect at ten times the rate in the morning versus the evening, does not surprise many scientists. But what is more impressive is that disrupted biological clocks – the lot of many of us in modern life – make infection easy all the time. And yet most dramatic, herpes virus directly targets the cell’s biological clock controls as a way to foster infection. In a 24/7 society, we may neglect the power of time in our lives.
Viruses know better.
What Was Found
The common influenza virus (RNA made) infects mice and their individual cells at ten times the rate in the morning versus evening. The same was true of herpes virus, a large DNA virus. The infectivity correlated with the activity of Bmal1, a major clock gene. Mice whose internal clock was disrupted remained highly susceptible to infection throughout the 24 hour day. Results appear to be similar in people.
What Does This Mean?
That just as drugs have different effects at different times of day – the antipsychotic haloperidol has effects that vary seven fold through 24 hours, and statins are useless if given in the morning – so do levels of infectivity.
Which means that shift workers, who frequently complain of colds, infections, and many other diseases, are more susceptible to widely varying viruses, just as they are more susceptible to heart disease, GI dysfunction, obesity and diabetes. Facts that should give pause to those who watch their cellphones through the night – much of the world of work is turning into shiftwork. Consider the effect on infectivity rates of young people who think sleep in the night is an unpleasant hiatus from social networking.
What About Other Studies?
These results are consistent with lots of other research. Minor disruptions of circadian rhythms have made people far more susceptible to getting colds. Relatively minor changes in sleep have similar effects. Animal studies have often shown that different times of day change what infections succeed, how they get in, and how they are fought.
What Does This Mean For Me?
Consider a few circumstances:
1. Travel. Studies argue that colds are far more common in airplanes. Sometimes this is blamed on the atmosphere of planes – dry as a desert and 6,000 feet up – and the remorseless recirculation of air, making plane travel the superbowl of viruses. What people may need to pay more attention to is the effect of biological clocks on their susceptibility to infection. If your clocks are off – and that is what jet lag is, inner clocks out of phase with where you are – you are far more liable to catch a cold or other illnesses. And even if your inner clocks are totally in phase, and you’re not sleep deprived – factors that will tend to be untrue for many business travelers – the people seated next to you may well be jet-lagged, making it much easier for them to get infected, and in turn infect you.
Or you are visiting Miami Beach and worried about Zika virus. You might want to make sure you adjust to jet lag a bit before venturing out in the morning – though Zika’s selective infectivity timing will need careful study.
2. Schools. Many parents get sick from their children, who in turn are learning to regulate their immune systems in a constantly shifting environment of viruses ceaselessly mutating. If viruses are more prone to replicate in people in the morning, hand washing before and during classes, and teaching kids to keep their hands away from eyes and nose become that much more important. It’s also an argument against early morning classes, which do more than decrease student performance – they fundamentally mess up children’s biological clocks.
3. Work – If flues are easier to pass in the morning, large, congregate business meetings during flu season may be more reasonably placed in later parts of the day.
Bottom Line
Time rules life – our lives, the lives of the people we live, our pets, and our pathogens. Knowing when to perform many tasks may be critical to their outcome.
And in a world that fears pandemics, time must be enlisted on our side. If viruses as important as herpes directly target our own biological clock machinery, this is both a warning and an opportunity.
The bugs have been using our inner time against us. Now it’s time to turn the tables. We, too, can time our countermeasures to the viruses that infect and harm us.
