For some it is an instrument of torture, for millions of others around the world a glorious outlet for unrecognised musical genius.

But the world of karaoke has been stricken by a fearful epidemic that threatens to silence Japan’s bars and the caterwauling of millions of amateur vocalists.

Japanese doctors report a surge in the condition known as “karaoke polyp”, a growth on the vocal cords caused by excessive warbling in bars and parlours. Formerly an affliction of middle-aged businessmen, the malady has spread among housewives and young people because of the continuing popularity of karaoke.

Ear, nose and throat clinics report a doubling in cases of karaoke polyps and the operation necessary to remove them. A surge of popular songs of especially high pitch, which put excessive strain on the vocal cords, is being blamed for the polyp plague.

The condition is exacerbated by the cold, dry Japanese winter, also a time for traditional end-of-the-year parties that frequently end in enthusiastic karaoke.

“I believe that the recent increase of popular songs with many high notes is causing this,” Ryuichi Mochizuki, head of the otolaryngology department of Osaka Kaisei Hospital, told the Asahi newspaper.

“When you sing a high note, your vocal cord is pulled back and forth and vibrates more vigorously than when you sing at a lower pitch. When such a note is sustained, it adds to the burden on the vocal cords.”

Karaoke machines, which play a background musical track of songs and display their lyrics on a video screen, are found in bars, private karaoke rooms and homes all over Japan. The first machines appeared in the 1970s and karaoke polyp was identified by Hiroyuki Fukuda, of the International Medical Welfare College, Tokyo, ten years later.

Thre are 47 million Japanese who indulge their passion every year in 133,000 karaoke rooms, although the numbers are down from the peaks of the late 1990s. It was in those days that psychologists identified another disorder associated with the craze: karaokephobia, or trembling, sweating and stomach cramps induced by the prospect of being forced unwillingly to sing in public.

Polyps of the vocal cords can also afflict teachers, clergymen, actors, lawyers and other professionals who spend a lot of time speaking out loud.

Humans have two vocal cords, each 1.5cm (0.6in) long, that vibrate against each other to produce speech. In normal conversation they vibrate a few hundred times a second. A soprano hitting a high note, however, can produce 1,200 vibrations a second, and such a pitch can damage the untrained throat.

The vocal cords can rub each other raw, causing polyps on one or both sides. Tobacco smoke and alcohol, traditional elements of the karaoke experience, increase the chances of this happening. The symptoms are huskiness and, occasionally, breathing difficulties, although not usually pain. Polyps can clear up of their own accord but if they harden they may require surgery to remove them.

One Japanese clinic, the Osaka Voice Centre, receives 20 patients with karaoke polyp every month and has performed surgery on 170 amateur singers last year, double the number in 2004. Doctors say that the only way to avoid the polyp is to exercise moderation — three full-throated karaoke songs in one evening are enough for the untrained voice.

Karaokeists should also stay within their vocal range, they say. Lower-pitched, growlier songs by the likes of Leonard Cohen and Bob Dylan are kinder to the vocal cords than those of high-risk musicians such as the Bee Gees.

The good news is that karaoke polyps are not dangerous and a timely throat examination can reveal other, more serious health problems at an early stage. “If your voice becomes hoarse and it keeps cracking, you must visit your doctor,” says Kazuhiko Goto, of the Osaka Medical Association, which offers health advice for karaoke enthusiasts on its website.

“It can lead to the diagnosis of diseases such as cancer of the larynx at an early stage.”

High risk

Last week’s karaoke Top Ten. Song with asterisk is dangerously high-pitched

1 * Crescent Moon by Ayaka

2 * Love Song by Shonan Wind

3 * Lovers Again by Exile

4 * Beyond 1000 Nights by Aqua Timez

5 * Cherry Blossom by Small Bag

6 Sky Boat by Tokio

7 * Let’s Meet Again by Seamo

8 * Sign by Mr Children

9 Dogwood by Hito Toyo

10 Powder Snow by Remio Romen

After the music, time to face the check-up

Dr Thomas Stuttaford

It used to be known as the sergeant-major’s voice but now the hoarse, rasping, breathy voice associated with heavy drinkers and smokers is known as a karaoke throat.

Vocal cords that are abused by yelling and shouting — as on the parade ground or by singing too loudly, particularly singing high notes, in British pubs or in Japan — develop nodules and polyps.

Similarly, irritating the cords by inhaling tobacco smoke, or alcohol fumes that rise up through the airways from the stomach and oesophagus, may cause the same condition. Any patient who is hoarse for more than three weeks should consult a doctor so that an ear, nose and throat specialist can do a biopsy of any nodules and polyps to make certain that none is malignant.

Benign karaoke nodules can be removed either by standard microsurgical excision or, increasingly, by laser surgery.

Although a laryngeal nodule is not premalignant, exposure to smoke and alcohol, rather than boisterous singing or shouting, may cause laryngeal malignancies, one form of which may arise on the cords, and this possibility must always be excluded.

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