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People who have myopia, or nearsightedness, are not able to see objects at a distance but only up close. It occurs when the cornea is either curved too steeply, the eye is too long, or both. This condition is progressive and worsens with time. More than 100 million people in the United States are nearsighted, but only 20% of those are born with the condition. Diet, eye exercise, drug therapy, and corrective lenses can all help manage nearsightedness.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Despite claims by manufacturers, the supplement known as Ginkgo biloba was shown in a study of more than 3,000 participants to be ineffective in reducing development of dementia and Alzheimer’s disease in older people.
Parkinson's disease is both chronic and progressive. This means that it persists over a long period of time and that its symptoms grow worse over time.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
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