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Only one in 10 cancer deaths is caused by the primary tumor. The vast majority of cancer mortality is caused by cells breaking away from the main tumor and metastasizing to other parts of the body, such as the brain, bones, or liver.
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).
In 1844, Charles Goodyear obtained the first patent for a rubber condom.
Hyperthyroidism leads to an increased rate of metabolism and affects about 1% of women but only 0.1% of men. For most people, this increased metabolic rate causes the thyroid gland to become enlarged (known as a goiter).
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.