Whether you’re dealing with the common cold, the flu or a stomach bug, you’ve probably noticed that your symptoms feel worse at night.
You’re not imagining things. Research suggests that your body’s circadian rhythms—as well as some other factors—can exacerbate your symptoms after sundown.
Along with regulating your sleep, your body’s circadian clocks help manage your immune system, says Michael Smolensky, a biological rhythm researcher and adjunct professor of biomedical engineering at the University of Texas. “When the immune system is activated”—like when you’re sick with the common cold—“its infection-fighting cells release a variety of chemicals, some of which induce inflammation in the infected tissues,” he explains.
This immune system activity helps kill or clear away the microorganisms that are making you ill. But the resulting inflammation causes or contributes to many of your symptoms—including fever, congestion or sore throat. Smolensky says that this immune system activity and the inflammation it produces is not constant, but instead is “highly circadian rhythmic.” As a result, “you tend to experience symptoms as most severe when your immune system kicks into highest gear, which is normally at night during sleep.”
This nighttime spike in immune system activity and inflammation can also bleed into the morning hours, he says. So if, despite your symptoms, you’re able to sleep through the night, you may find that you feel worse first thing in the morning when you wake up.
The afternoon and early evening, meanwhile, are times of the day when your immune system tends to mellow out, Smolensky’s research shows. It’s not unusual to feel a bit better around those times, but then to have symptoms come roaring back later at night.
A few other factors could contribute to the nighttime misery you experience when you’re sick.
The absence of distractions may heighten your perception of some symptoms, says Dr. Rob Danoff, a family physician with Philadelphia’s Aria-Jefferson Health. That headache or sore throat you mostly ignored while watching TV may seem much worse when you’re lying in bed with nothing else to occupy your attention, he says.
Also, lying down could stoke some congestion-related symptoms. “During the day when we’re up and about, the mucus tends to drain down and doesn’t accumulate towards the back of our throat like it does when we are lying down,” Danoff says.
If congestion is your biggest issue, it may be helpful to elevate your head with a few pillows, he says. This can help your mucus drain, preventing a big build-up in the back of your throat or in your sinuses. And because you drink less at night than you do during the day, nighttime snot can become viscous and clog your nose and airways. Drink plenty of fluids during the day to keep your mucus thin and watery, not thick and gunky, Smolensky says.
Another remedy: take something to treat your most bothersome symptoms. Whether you rely on over-the-counter decongestants or natural curatives like chicken soup (which research has linked to a drop in inflammation among people with respiratory tract infections), these common therapies can provide short-term relief, says Dr. Jeffrey Steinbauer, a professor of family and community medicine at Baylor College of Medicine.
A good night’s sleep may be among the best ways to get over your illness. So using all the weapons at your disposal to ease your nocturnal symptoms is a smart idea.