A
hiccup is an involuntary spasm of the
diaphragm that typically repeats several times a minute. The sudden rush of air into the lungs that's created by each spasm causes the
glottis to close, creating the "hic" noise. A bout of hiccups generally resolves by itself, although many home remedies are in circulation to shorten the duration. The medical term for hiccuping is
singultus.
While many cases develop spontaneously, hiccups are known to develop often in specific situations, such as eating too quickly, taking a cold drink while eating a hot meal, eating very hot or spicy food, laughing vigorously or coughing, or drinking an excess of an alcoholic beverage. Hiccups may be caused by pressure to the
phrenic nerve (located in the neck region) by other anatomical structures. Interestingly, it is reported that 30% of chemotherapy patients suffer singultus as a side effect to treatment.
One possible beneficial effect of hiccups is to dislodge large chunks of food, which have become stuck in the esophagus, or which are traveling too slowly. When a large piece of food is swallowed, which the natural peristalsis of the esophagus is unable to move quickly into the stomach, it applies pressure on the
phrenic nerve, invoking the hiccup reflex. This causes the diaphragm to contract, creating a vacuum in the thoracic cavity, which creates a region of low pressure on the side of the lump of food nearest the stomach, and a region of high pressure on the side of the lump of food nearest the mouth. This pressure differential across the food creates a force, which assists peristalsis.
The hiccup mechanism likely evolved as an aid to peristalsis in our ancestors. It only now appears to offer little benefit, because humans are upright, so that gravity assists peristalsis, making it very unlikely for food to become lodged in the esophagus.
The
Guinness World Record for the longest continuous bout of hiccups (1922–1990) goes to Charles Osborne (1894–1991) from Anthon, Iowa. The hiccups started in 1922 at a rate of 40 times per minute, slowing to 20 and eventually stopping in February 1990 – a total of 68 years.
