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What Causes Hiccups?

Did you ever have a case of synchronous diaphragmatic flutter? Sounds pretty serious, right? Well, it’s not. Synchronous diaphragmatic flutter, also known as SDF, is the medical term for a simple case of the hiccups.

Most people will experience them at one time or another, but what causes hiccups? That’s what we’ve come here to find out.

Triggers for Hiccups

There isn’t just one thing that causes hiccups. There are many triggers.

What Causes Hiccups?There seems to be a link between digestive upset and hiccups, but this is not always the case. There are some things, however, that have been found to increase the likelihood of getting a case of the hiccups.

  • Overeating
  • Eating too quickly
  • Drinking carbonated drinks
  • Eating very dry bread
  • A sudden increase or decrease in the temperature
  • Eating spicy food
  • Drinking alcohol
  • Taking certain medication


Scientists know what happens physically during a hiccup – an involuntary contraction of the diaphragm coupled with a contraction of the larynx – but they don’t know exactly why. However, there are a few current theories.

Why Do We Hiccup?

Now that we know what causes hiccups, we must answer the question: why?

The weird truth is that hiccups don’t really accomplish anything.  Burping helps us reduce gas in the digestive system.  Coughing is an effective way to clear out the airways.  But hiccups don’t really do anything helpful.   So, evolutionarily, why do we do it?

We Once Had Gills

One theory is that hiccups are an evolutionary hold-over from one of our oldest ancestors, the fish.

From an article in the Guardian profiling Neil Shubin’s book Your Inner Fish:

Hiccups are triggered by electric signals generated in the brain stem. Amphibian brain stems emit similar signals, which control the regular motion of their gills. Our brain stems, inherited from amphibian ancestors, still spurt out odd signals producing hiccups that are, according to Shubin, essentially the same phenomenon as gill breathing.

A hiccup is the sudden contraction of the “breathing in” muscle, combined with an almost immediate closure of the glottis.  While this doesn’t do much for us, an almost identical mechanism is what allows fish to breathe.

A Lung FishA Lung Fish

For early breathers such as the Lung Fish, and the Gar, a “hiccup” is the only way to pass water through the gills without swallowing it into their lungs.

A Mammalian Phenomenon

Though fish may explain why hiccups were “invented”, they don’t explain why we still hiccup, and more interestingly, why it’s primarily a mammalian phenomenon.

Though nothing definitive has been proven, evidence suggests that hiccuping has persisted as a way to help young mammals when breast-feeding from their mothers. Some evidence that points us in this direction:

  • Only mammals seem to hiccup.
  • Hiccuping occurs more frequently in infants (even in-utero).

Daniel Howes suggests in the journal BioEssays that hiccuping is basically a form of burping that is helpful for suckling infants:

Young mammals depend on milk consumption for their nutrition. The continuous nature of suckling means that it has to be coordinated with respiration and the result can be swallowed air. A reflex that helps remove swallowed air would significantly increase the stomach’s capacity for milk. This also explains why the hiccup is so much more frequent in infancy.

So, if I had to cobble together an evolutionary hypothesis, it seems that hiccuping was first needed by our early-breathing aquatic ancestors, and it has been adapted as a useful burping mechanism for suckling infants.

As for adult hiccups, well, some habits are just hard to break.

As Myth Busters would say, this theory is: PLAUSIBLE. Further research needs to be completed before we can be sure.

Bonus: What Causes Long-Term Hiccups?

A man named Charles Osborne suffered with a case of hiccups that lasted 68 years.

From 1922 until 1990 it is estimated that Osborne hiccupped about 430 million times. This is the world record for longest case of the hiccups, and it’s unlikely that you will ever experience anything even close to that. Still, there is a chance you could develop a long-term case of the hiccups.

Here are some of the possible causes of long-term hiccups:

  • Damage to the nerves that serve the diaphragm muscle: Such damage could be cause by a tumor, reflux or a sore throat.
  • A disorder in the central nervous system: This could be caused by a stroke, tumor or brain injury.
  • Metabolic issues: This includes kidney failure or diabetes.
  • Drug use: Certain drugs such as steroids, barbiturates or opiates could trigger a long-term case of the hiccups.

We’re going to keep our ear to the ground on this whole hiccup thing.  Want to be notified when new research comes to light? Join us below!

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