There are two intriguing cases studies in the latest edition of the journal Sleep and Breathing of people with persistent yawning.
Normally, recurrent yawning might be put down to tiredness, but in these cases, both women slept well. They could, however, reduce their yawning by cooling themselves – suggesting that yawning and heat regulation may be linked.
Both of their symptoms are very similar. Each complains of unpredictable and uncontrolled yawning attacks lasting from 5 to 45 min. During these excessive yawning episodes, they experience deep, recurrent, overwhelming yawns that cause their eyes to water and nose to run. Occurring one to 15 times a day, these attacks are very aversive and debilitating, and both patients report feeling ill and exhausted following an attack. The most common diagnosis is a sleep disorder, although neither patient reports sleep problems.
These cases include features consistent with a diagnosis of thermoregulatory dysfunction. Both patients report that nasal breathing and/or applying cool cloths to the forehead can provide temporary relief and/or postpone the onset of an attack…
Taking a cold shower or swimming in cold water after the onset of an attack produces complete remission of symptoms for the South African woman. Both patients report feeling cold during or after an attack and experience goose bumps and shivering which may be a consequence of overcompensation by cooling mechanisms activated during thermoregulatory dysfunction.
Although it is still not well understood why we yawn, this gels with some growing evidence that heat regulation may be at least part of the story.
In one intriguing study [pdf], nasal breathing and forehead cooling reduced ‘contagious yawning’ where yawns are more likely to be triggered when we see other people doing the same.
Link to PubMed entry for yawning case studies.