Circadian rhythms’ might sound like an ’80s synth-pop band, but they’re key to our biology and our health. They’re the physical, mental, and behavioral changes all organisms, including humans, have evolved to respond to – our internal body clocks controlling virtually every biological system, from our sleeping and waking cycles to mood and performance levels, and metabolic, reproductive and immune systems. And those immune systems have never been more important than in the war on Covid-19.
To keep our immunity strong and be in the best physical and mental shape to fight infection, most of us need seven to eight hours of sleep a night. ‘A few people can get by with five hours and wake to feel refreshed, which is what counts,’ says Michelle Baker, a Durban-based clinical psychologist with a special interest in sleep. But regularly getting less than five hours has been linked to a raft of ills, from increased inflammation, high blood pressure and insulin resistance to weight gain, cardiovascular disease, impaired blood sugar regulation, and the big one right now – impaired immunity.
The impact of poor sleep on immunity has been shown in several studies, such as one done last year at the University of California, which found that people who got less than six hours of sleep a night were four times more at risk of catching a cold when exposed to the virus than those who had seven hours or more. ‘Another study showed an increased risk of catching pneumonia with less than five hours of sleep,’ says Dr. Alison Bentley, who runs a sleep therapy clinic at the Wits University Donald Gordon Medical Centre.
The reason comes down to our T cells – white blood cells that ward off infection by attacking and destroying virus-carrying cells before they can multiply. Sleep boosts our production of T cells; getting too little sleep weakens it. Crucial too is our production of proteins called cytokines, secreted by certain cells of the immune system, that help the immune system respond fast to foreign substances. ‘Cytokines direct cells to head towards infections to fight them, and the brain disposes of waste during sleep,’ Baker says.
You need a proper night’s sleep to replenish these cells and proteins and ward off a disease like Covid-19. But many of us are struggling to get our ZZZs because of stress about coronavirus, job security, the economy, the political implications, and the uncertain future.
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