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Hiccups: A Scientific Mystery

Hiccups: A Scientific Mystery

     Although hiccups are extremely common, the medical sciences have yet to figure out what causes them. They remain one of the unsolved mysteries of the human body. Maybe that’s not totally surprising. After all, they don’t usually indicate that something is seriously wrong and they normally stop on their own—usually within a few minutes.

     So, it’s not seen as a pressing problem that needs a lot of scientific research and medical investigation. So what are hiccups?

     A hiccup involves two very distinct actions:

  1. The diaphragm, the main muscle that powers the lungs, goes into spasm or contraction.
  2. The epiglottis, a flap of tissue behind the tongue, slams shut over the top of the windpipe leading to the lungs. This is known as “glottis closure”: and the sudden reflexive motion produces the typical “hic” sound. But there is no consensus about whether this sequence begins in the chest or the throat. In other words, does the spasm in the diaphragm trigger the epiglottis to shut, or vice-versa?

Hiccups actually illustrate a much larger story about the complex reflexes that keep us alive. The mouth is used to take in solids, liquids and air and they all must end up in the right place. If food or liquid goes down the wrong way and enters the lungs, it can lead to a potentially deadly infection known as aspiration pneumonia. To prevent this from happening, a reflex triggers the epiglottis to cover the opening to the lungs when you swallow, thereby funnelling food or drink down the esophagus into the stomach. I find it amazing that we can breathe air into our lungs and ingest food and drink into our stomachs and keep these two paths separate and yet we all take this activity for granted.

     It’s possible that this reflex could be hyperactive in young people and that extra responsiveness might explain why hiccups are fairly common in babies and young children.

     As we age, the muscles that cause the epiglottis to spring into action might become less twitchy. As a result, older adults seem to have fewer bouts of hiccups than the young.

     However, in people with certain neurological conditions—such as Parkinson’s disease, amyotrophic lateral sclerosis (ALS) and stroke—this reflex can stop functioning normally. In this case liquids and solids may end up in the lungs and aspiration pneumonia is a common cause of death among people with these conditions.

     Keeping annoying hiccups in perspective, it seems to be a protective response. Although the timing is a bit off. The epiglottis seals the windpipe at the wrong moment when it doesn’t really need to. In very rare cases, tumours, nerve damage or other medical ailments can cause persistent hiccups lasting hours, days or even longer and the patient needs to see a doctor or go to emergency.

     According to the Guinness World Records, an Iowa farmer, Charles Osborne, had a case of continuous hiccups lasting for 68 years, from 1922 to 1990. They apparently started when he was attempting to weigh a hog before slaughter and the animal fell on top of him.

     The unfortunate farmer had several unsuccessful operations to correct the problem. The hiccups finally stopped on their own, but he died a year later from a bleeding ulcer which the surgeons said was unrelated.

     Of course the Iowa farmer represents an extreme case and most of the time hiccups only last a few minutes.

     On the internet, you’ll find much speculation about the things that might trigger a hiccup attack, ranging from an overly full stomach to excessive alcohol consumption. You’ll also come across scores of home remedies, including holding your breath, swallowing granulated sugar and pulling hard on your tongue. When I practised pharmacy there was a drug for people whose attack would not subside. It was called Largactil (chlorpromazine) and only used for people with severe psychosis but one pill seemed to work for a patient whose hiccups would not stop.

     Yet, it’s difficult to prove any of these approaches will work because most hiccups start and stop automatically—for no apparent reason. So far I have not found one controlled randomized study showing than anything will stop hiccups. Until that happens, hiccups will remain a mystery for some time to come. [print_link]