Dear Christopher Cat: Does purring have any health benefits?

Christopher Responds: Yes. Many animal species purr, including almost all cats except lions.

The purring sound is made by air moving through the glottis, the vocal apparatus in the throat that consists of the vocal folds (cords) and the slit-like opening between them. The oscillations in sound are controlled by the brain, diaphragm, larynx and the nerves that connect these structures.

Mother cats purr to help their kittens locate them to nurse. Newborn kittens can’t see or hear until two weeks of age, but they can feel the vibrations of their mother’s purring.

Adult cats purr when they are content, but also when they’re anxious, just like humans who bite their fingernails. In addition, cats purr when they’re giving birth, injured or in pain.

Domestic cats usually purr at a frequency of 20 to 30 Hz, though the frequency varies from 18 to 150 Hz depending on the cat’s emotional state.

Purring at 18 to 35 Hz increases joint mobility. At 25 to 50 Hz, purring increases bone strength, stimulates bone fracture repair and promotes healing of injured muscles and tendons. At 100 Hz, purring decreases pain and improves chronic respiratory disease.

Research in humans demonstrates that vibrations at frequencies of 50 to 150 Hz decrease acute and chronic pain. Vibrations of 100 Hz on the chest ease breathing in human patients who are short of breath.

It’s tempting to wonder whether the built-in healing system called purring could be the magic that gives cats their nine lives.