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October arrived and the chemist rearranged itself overnight. Elderberry syrup at the front, echinacea beside it, vitamin C in doses no human has ever needed, zinc lozenges at the till. Somebody at work is already coughing.
Researchers settled this question about a decade ago, in the only way that really answers it. They measured how people actually slept for a week, locked them in a hotel, and squirted live cold virus into every nose. Then they waited to see who got sick.
You do not catch everything going round because you were born with a weak constitution. Your defences have been working a short shift.
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Nothing in that October aisle has ever been tested the way sleep was tested, with a real virus and a locked door.
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THE SHIFT YOUR DEFENCES WORK
Your immune system does much of its real work while you are unconscious. T cells, the units that recognize an invader and remember it afterwards, become markedly better at sticking to their targets during sleep, and the signalling chemicals that coordinate a response rise overnight on a schedule.
Cut that window short and the response is slower off the mark. A virus that would have been met at the door gets several unopposed hours to establish itself. Same exposure, same virus, entirely different outcome.
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THE EVIDENCE
Aric Prather at UCSF and Sheldon Cohen at Carnegie Mellon tracked 164 adults with wrist monitors for a week, then quarantined them and administered rhinovirus by nasal drops (Sleep, 2015). Anyone averaging under six hours was 4.2 times more likely to develop a cold than those getting more than seven. Thirty-nine percent of the short sleepers fell ill, against 18%. Smoking, stress, age and income were all measured, and sleep outranked every one of them.
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Note where the line fell. Not at eight hours or nine, but somewhere between six and seven, which puts an enormous number of women on the wrong side of it by about forty minutes.
THIS MONTH, IN ORDER OF EFFORT
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Treat seven hours as the line, particularly through the autumn.
Those monitors measured sleep rather than time in bed, which runs twenty or thirty minutes shorter for most people. Lights out at eleven for a seven o'clock alarm leaves you closer to the risky side than the figure on your clock suggests.
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Guard the nights either side of your flu vaccination.
Antibody response to a vaccine has repeatedly come out weaker in people who were short of sleep around the appointment. Book it for a week when nothing is on, which costs nothing and may be the cheapest improvement available to that jab.
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At the first scratchy throat, cancel the evening rather than the morning.
Most of us respond to early symptoms by taking something and carrying on, then paying for it later in the week. Going up two hours early on that first night does more than anything you can buy at a counter.
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When somebody at home goes down, protect your own night first.
Nursing a household through a virus while sleeping five hours is precisely how the carer ends up ill a week later. Sleeping in another room for a few nights is not unkind, and it keeps one functioning adult in the building.
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And one more thing...
Of everything crowding that October display, the compound with the most serious immune research behind it is also the one with no marketing budget. Beta-glucan, a fiber from oats and baker's yeast, has been studied for how it primes the cells that meet a virus first, with a reasonable run of trials in people under physical stress. It costs very little and is spectacularly boring. You have been eating a version of it in porridge your whole life.
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QUICK QUESTION
Do you catch whatever is going round at work or at home?
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