For the vast majority of us, a hiccup is no more than a slight nuisance that goes away quite quickly on its own, or with a little coaxing from one of the huge number of folk remedies available. Hiccups, however, can be a serious affliction - they have even killed some long-term sufferers.
But what exactly is a hiccup? Is your breath going out or in? If you think about it, you realise that there is a feeling of inhaling. This is, in fact, exactly what is going on: your diaphragm pulls down as if you were taking a big breath, and your so-called 'inspiratory' muscles hastily work to make room for the incoming air in your chest. Next, however, instead of air rushing in to fill the space being created in your chest, something else happens. Within thirty-five milliseconds, a signal reaches your glottis - the little flap that covers your airway (or 'trachea') when you swallow so that food doesn't go down it - telling the glottis to slam shut. This keeps any air from actually getting into your lungs - and causes the "hic" associated with a hiccup.
The force with which your diaphragm and other muscles move is a bit like what happens in hyperventilation when you breathe in and out very rapidly. In fact, experiments on a person with a tracheotomy showed that when hiccups occur without closure of the glottis, air rushed in and out so violently that it led to hyperventilation.
But why do we hiccup? The short answer is that no one knows. Thousands of years of speculation have brought us no closer to a conclusive answer. Nonetheless, one theory has hovered in the background for many years: the idea that hiccups have a function during fetal development and that the adult version is just a residual reflex left over from that time.
Fetal hiccups were reported in 1899, and then confirmed once ultrasound became available. Premature infants are thought to spend a phenomenal 2.5% of their time hiccuping. Thus some people propose that hiccups allow a fetus - which can't actually take a breath in the womb as there is no air available - to exercise the inspiratory muscles that it will need immediately after birth in order to breathe air. In other words, hiccups may allow the fetus to practise vital 'breathing' motions while protecting it from inhaling amniotic fluid.
Whether or not this is, in fact, the physiological origin of hiccuping, most people find that certain activities - such as eating too much, or drinking carbonated beverages - precipitate them. The theory behind this is that distension of the stomach may irritate the diaphragm and cause it to go into a spasm. However, no one factor has been shown to stimulate hiccups in everyone. A few years ago, researchers reported that they could reliably cause hiccups in four out of ten subjects by stretching part of the oesophagus, but obviously this technique is not a universal hiccup stimulator.
Folk remedies abound for curing hiccups. Some people have even gone so far as to copyright their hiccup cure (see the website www.mastersweep.com/curehiccups.htm). The favourite but dubious advice seems to be to drink water from the wrong side of a glass; other classics recommend holding your breath or breathing into a paper bag, which may have a more scientific basis as researchers have found that an increased level of carbon dioxide (the gas that collects in the paper bag) does help to control or stop hiccups.
A more sinister side of hiccuping appears when they refuse to stop, even after a few days. One poor man, Charles Osborne, lived with continuous hiccups for more than 63 years. He got little sleep, suffered from nosebleeds and vomiting, and was forced to live on a diet of blended foods.
But not everyone can weather the consequences of intractable hiccups. There is a medical case report entitled "A fatal case of hiccups". And even famous folk are not immune to the problem: Pope Pius XII, for example, is reported to have suffered days of hiccuping associated with gastritis.
On a less anecdotal level, causes and treatments of chronic hiccups (officially called 'singultus') do appear in the medical literature. Doctors have reported brain tumours, infections and gastric ulcers, among others, as causes of prolonged hiccuping. Although not everyone agrees that drugs can be a direct cause of hiccups, there are many reports that chronic hiccups can be a rare side effect of medications such as corticosteroids (immune-system suppressants) and benzodiazepines (very strong tranquillisers).
In cases of severe hiccups, physicians have attempted some drastic remedies, including blocking the phrenic nerve, which controls the contractions of the diaphragm, in the hope of halting its spasms. Two clinicians have also published a report in The Lancet on the use of marijuana to treat a patient with chronic hiccups. One drug, though, seems to have a beneficial effect for many sufferers: it is called Baclofen and is used to treat a number of diseases involving muscle tightness and spasms.
However, the treatment of chronic hiccups is generally by trial and error. Indeed, despite hundreds of articles published on the topic, hiccups still seem to make doctors scratch their heads. A satisfactory explanation for either the start or the end of a bout of the hiccups is usually elusive; each person seems to constitute a unique case. How fortunate, then, that for most of us all that we need to do to combat this mysterious and uncontrollable bodily function is to contort ourselves into bizarre shapes while water dribbles from the wrong side of a glass into our mouths and down our shirts.
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Wunsch, H. Don't hold your breath. Nature (1999). https://doi.org/10.1038/news990819-12