Chinese essential tremor patient Chu Shuqin finished a full marathon within 2 hours and 33 minutes during the Medtronic Twin Cities Marathon held last month in Minnesota. [Photo provided to China Daily]

When someone says "ET", many people will perhaps instantly think of the alien in the 1982 American science fiction fantasy movie E.T. the Extra-Terrestrial. Very few know that "ET" also stands for essential tremor, a painful chronic disease.

As its name suggests, the disease is a nervous system disorder that causes uncontrollable and rhythmic shaking. It can affect any part of the body, especially the upper limbs. Sometimes it affects the head and the voice.

The disease can occur at any age, but is more common among those in their 40s, and those older than 60. It impairs daily functions. As it worsens, even drinking water from a cup without a straw becomes difficult.

Among the general population its incidence rate is between 0.3 and 1.7 percent, and among people older than 45 and people older than 65, the incidence rates are 5.5 and 10.2 percent, respectively, says Li Jianyu, a senior specialist in neurology and movement disorders at Xuanwu Hospital in Beijing.

Also, many patients, especially seniors, do not seek treatment when they first suffer the tremors because they think it is normal for older people to suffer the condition.

"Essential tremor may be novel for many, but it is not that uncommon," says Li.

"It is a pity that many people, including medical personnel, are not aware of the condition."

Chu Shuqin, a 49-year-old woman from Hebei province, knows well the cost of ignorance about the disease.