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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
On average, someone in the United States has a stroke about every 40 seconds. This is about 795,000 people per year.
Vaccines prevent between 2.5 and 4 million deaths every year.
The senior population grows every year. Seniors older than 65 years of age now comprise more than 13% of the total population. However, women outlive men. In the 85-and-over age group, there are only 45 men to every 100 women.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.