What is the Purpose of Hiccuping?

Posted on Categories Discover Magazine

We’re all familiar with (hic) the mildly uncomfortable sensation (hic) that is hiccups (hic). Perhaps you swallowed a bit too much air at once, downed your lunch with incredible speed or took a swig of something overly carbonated or alcoholic. Maybe you laughed at a phenomenal joke for way too long — or maybe you simply became over-excited for no reason at all. The fact is, any one of these things (and a great many more) can set off a round of hiccups. And while most attacks occur sparingly and linger for only a few minutes, they can sometimes spiral out of control. Nearly 4,000 Americans are hospitalized for hiccups each year, after all. All this begs the question: At what point in our evolution did humans pick up hiccuping? And, beyond being an inconvenience, what is its purpose? Scientists have a few theories. Anatomy of a Hiccup Though the act seems like a fairly simple chain of events, hiccuping can be pretty complex from a biological perspective.  Basically, your brain tells the diaphragm — the large, dome-shaped muscle situated below your lungs that helps you breathe — to suddenly move downward. That powerful contraction forces air into your throat involuntarily, but it gets stuck on its way to the lungs. Why? Because at the same time, the change in pressure causes the opening between your vocal cords, called the glottis, to snap shut. As a result, you make that characteristic hic sound and maybe even experience a full-body jerk for good measure. Read More: Deep, Slow Breathing: An Antidote to Our Age of Anxiety? Scientists still aren’t sure exactly why the brain kicks the whole process off to begin with, or what brings it grinding to a halt after minutes or hours. In the vast majority of cases, serious disease isn’t to blame.  But occasionally, hiccups persisting longer than 48 hours do accompany structural damage or infectious or inflammatory disorders. In the case of one person, the root cause of a chronic bout of hiccups was a single hair brushing against their eardrum. In another case, however, a young man found relief from his four-year-long stretch of hiccups only after a life-saving surgery removed a tumor in his brain stem. What’s the Point of Hiccuping? With all these disadvantages, and hardly any advantages to speak of, you might be wondering if hiccups serve a purpose at all. Well, some scientists have argued in the affirmative. They point to the fact that even human fetuses hiccup, long before they’re born. In fact, the diaphragmatic spasms are more common in infants than in adults. It’s possible that this reflex helps prevent fetuses from breathing in amniotic fluid while still in the womb; likewise, it could prevent newborns from choking on milk while breastfeeding. And still others have proposed that hiccuping in the womb trains a fetus’ respiratory muscles for all the breathing they will have to do after birth. But humans aren’t the only animals that hiccup; pretty much any species that breathes exclusively air — including all mammals — can suffer the same fate. (Birds and reptiles, on the other hand, get a free pass.) In fact, that’s the reasoning behind another theory, which posits that hiccups are merely an evolutionary “leftover” in mammals, dating all the way back to our fishy ancestors. When these species transitioned from gill-based breathing in the water to lung-based breathing on land, while still possessing both organs, a breathing system that allowed them to quickly close the glottis and direct water only to the gills was beneficial. We see a similar process play out on a smaller scale when tadpoles grow up and transition into frog-hood. And that may not be a coincidence; believe it or not, the neural patterning that generates a hiccup in humans is almost identical to the neural patterning involved in respiration in amphibians. Tips and Tricks for Hiccups So far, the world record for longest attack of hiccups still belongs to Charles Osborne, an American man who “started hiccoughing in 1922 while attempting to weigh a hog before slaughtering it.” Unable to find a cure for 68 years, he hiccuped an estimated 430 million times. A physician at the Mayo Clinic did successfully pause his hiccups, but only for as long as Osborne could breathe in a poisonous mixture of carbon monoxide and oxygen. (Spoiler alert: It wasn’t very long.) In the end, the hiccups went away of their own accord in early 1990 — around a year before Osborne’s death at age 97. Nowadays, a quick Google search will yield a plethora of “tried and tested” cures: give yourself a fright, drink ice-cold water, hold your breath, swallow sugar, bite into a lemon, hug your knees … the list goes on.  But the sad truth is, none of these remedies are backed by science. Some experts tentatively advise techniques that increase carbon dioxide levels in the lungs and relax the diaphragm (such as breathing into a paper bag). Others recommend exploring breathing techniques, aiming for a respiration rate that rebalances your nervous system and eases physiological stress. For persistent hiccups, doctors sometimes turn to prescriptions like gabapentin, baclofen and chlorpromazine. A truly tried and tested remedy, however, is likely dependent on us fully understanding what causes hiccups in the first place. In which case, don’t hold your breath!

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