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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
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.
Increased intake of vitamin D has been shown to reduce fractures up to 25% in older people.
Alzheimer's disease affects only about 10% of people older than 65 years of age. Most forms of decreased mental function and dementia are caused by disuse (letting the mind get lazy).
The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.