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Asthma is the most common chronic childhood disease in the world. Most children who develop asthma have symptoms before they are 5 years old.
Of the estimated 2 million heroin users in the United States, 600,000–800,000 are considered hardcore addicts. Heroin addiction is considered to be one of the hardest addictions to recover from.
Not getting enough sleep can greatly weaken the immune system. Lack of sleep makes you more likely to catch a cold, or more difficult to fight off an infection.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
The Romans did not use numerals to indicate fractions but instead used words to indicate parts of a whole.