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Lifestyle choices cause cancer: tobacco, diet, exercise, alcohol, tanning choices, and certain sexually transmitted diseases are the major risks. "Most cancers are related to known lifestyle factors."[10]
There is also a growing body of research that correlates cancer incidence with the lower levels of melatonin produced in the body when people spend more time in bright-light conditions[citation needed], as happens typically in the well-lit nighttime environments of the more developed countries. This effect is compounded in people who sleep fewer hours and in people who work at night, two groups that are known[citation needed] to have higher cancer rates.
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