Someone told me sleeping with a sports bra is bad over night. is this true?

Needs more research: Good question! a famous study claims women who wear a bra 24 hours a day have a much higher incidence of breast cancer, but it has received a lot of criticism because women who wear bras at nite tend to be overweight & that is more likely the cause of increased risk. See http://breastcancer.About.Com/od/riskfactorsindetail/a/bras-breast-cancer.Htm & (anti-bra): http://www.Brafree.Org/faq.Html.