Thirty-Five Milliseconds to Make a Sound
A hiccup — scientific name singultus, from the Latin for "sob" — is an involuntary contraction of the diaphragm, the sheet of muscle beneath your lungs that drives breathing. Technically it is a myoclonic jerk, a sudden involuntary muscle twitch.
The famous noise is not the twitch itself. Once triggered, the reflex arc causes the diaphragm to contract, and then the glottis — the space between the vocal cords — slams shut in about 35 milliseconds. That abrupt closure of an incoming breath is what makes the "hic".
So a hiccup is really two events: a gulp of air pulled in, and a door shut on it a thirtieth of a second later. Two nerves run the show — the phrenic nerve, which controls the diaphragm, and the vagus nerve, which is part of the reflex pathway. Nerve damage from surgery can set hiccups off, which is a clue to how mechanical the whole thing is.
Sixty-Eight Years Without Stopping
Hiccups may come singly or in bouts, and the rhythm between them tends to stay relatively constant — your body picks a tempo and keeps it.
A bout normally resolves itself without intervention. Normally.
Charles Osborne holds the record that makes everyone wince. He hiccupped continuously from 1922 to 1990 — 68 years — for an estimated 430 million hiccups, and was entered in Guinness World Records for it. He lived an entire adult life, through two world wars and the moon landings, hiccupping. It is the clearest possible demonstration that this is a reflex and not a behaviour: nothing about it was under his control, and no remedy reached the circuit that was firing.
A Leftover From Breathing Underwater
Why do hiccups exist at all? There are two main hypotheses, and both suggest hiccups are less a malfunction than a relic.
The amphibian, or tadpole, hypothesis proposes that hiccups are an evolutionary remnant of primitive gill-breathing. The supporting detail is genuinely striking: the motor pathways that enable hiccuping develop in fetuses before the pathways for normal lung ventilation do. The old circuit is wired in first.
The suckling hypothesis is more recent and more practical. It suggests hiccups evolved to help nursing mammals burp air out of the stomach, clearing room for more milk. It fits the observation that hiccups are especially common in babies — and fetuses hiccup in the womb well before there is any air to hiccup on.
Peanut Butter and Standing on Your Head
Because a bout usually ends by itself, almost any remedy appears to work — which is exactly why there are so many of them and why they are all defended so passionately.
The folk catalogue includes headstanding, drinking water upside-down, breathing into a bag, peanut butter, and sugar on the tongue. Common triggers are less exotic: rapid eating, alcohol, carbonated drinks, spicy food, and swallowing too much air.
What unites the more plausible remedies is that they interfere with the reflex circuit rather than the stomach — holding breath and rebreathing into a bag raise carbon dioxide levels, while swallowing something awkward stimulates the throat and the vagus nerve along it. Where hiccups turn chronic, medical treatment is occasionally necessary. For everyone else, the honest advice is the least satisfying: wait.
