Sighing: A Life-Saving Reflex. Scientists Discovered How.


Sighing is not just a sigh anymore. Growing up, our parents used to tell us it’s rude to sigh. Now, the advice doesn’t seem valid anymore, because heaving an unconscious sigh is a life-sustaining reflex that helps preserve lung function, and researchers have just uncovered the switch in our brain that controls it.

The team of scientists identified two tiny clusters of neurons in the brain stem that automatically turn normal breaths into sighs when our lungs need some extra help – and they do this roughly every 5 minutes (or 12 times an hour), regardless of whether or not you’re thinking about something depressing.

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According to Mark Krasnow, a professor of biochemistry and Howard Hughes Medical Institute Investigator at Stanford University,

Unlike a pacemaker that regulates only how fast we breathe, the brain’s breathing centre also controls the type of breath we take,

It’s made up of small numbers of different kinds of neurons. Each functions like a button that turns on a different type of breath,

He further explains.

One button programs regular breaths, another sighs, and the others could be for yawns, sniffs, coughs and maybe even laughs and cries.

Pro. Krasnow and his colleagues carried out the research by screening mouse with more than 19,000 gene-expression patterns in the animals’ brain cells, where they discovered about 200 neurons in the brain stem that manufacture and release one of two neuropeptides,

They found that blocking one of the peptides cut the animals’ sighing rate in half. Silencing both peptides halted the mice’s ability to sigh completely.

Speaking about the discovery, he added,

These molecular pathways are critical regulators of sighing, and define the core of a sigh-control circuit. It may now be possible to find drugs that target these pathways to control sighing.

Sighing is vital to lung function, and thus to life, Feldman emphasized.

A sigh is a deep breath, but not a voluntary deep breath. It starts out as a normal breath, but before you exhale, you take a second breath on top of it.


On average, a person sighs every five minutes, which translates into 12 sighs per hour.

The purpose of sighing is to inflate the alveoli, the half-billion, tiny, delicate, balloon-like sacs in the lungs where oxygen enters and carbon dioxide leaves the bloodstream. Sometimes individual sacs collapse, though.

When alveoli collapse, they compromise the ability of the lung to exchange oxygen and carbon dioxide.

Feldman went on,

The only way to pop them open again is to sigh, which brings in twice the volume of a normal breath. If you don’t sigh, your lungs will fail over time.

The ability to limit the sighing reflex could prove useful in anxiety disorders and other psychiatric conditions where sighing grows debilitating.

The mechanism behind the emotional roots of conscious sighing remains a mystery.

Feldman said,

There is certainly a component of sighing that relates to an emotional state. When you are stressed, for example, you sigh more. It may be that neurons in the brain areas that process emotion are triggering the release of the sigh neuropeptides — but we don’t know that.

But while we wait for an answer, don’t feel bad about sighing to your heart’s content. Your alveoli will thank you for it.

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Sources: UCLA and  ScienceAlert