Soma Grismaijer and Sydney Ross Singer, Authors of the book Dress to kill, evidence that bra-wearing may be a major risk factor associated with breast cancer: women who wear tight-fitting bras 24 hours a day are 125 times more likely to have breast cancer than women who do not wear bras at all. Their interpretation is that tight clothing inhibits the proper functioning of the lymphatic system (an internal network of vessels and nodes that flushes wastes from the body) and leads to a buildup of carcinogenic compounds in the constricted areas. Amazon.com