"SLEEPING WITH BRA DOESN'T CAUSE BREAST CANCER" - RESEARCH

You've probably heard the unfortunate rumors that wearing a bra to sleep causes breast cancer, or that it causes breast sagging because it supposedly weakens breast tissue. But aside from the fact that it may not be all that comfortable, there's no evidence to suggest that there are negative health effects to wearing a bra to sleep.

As Amber Guth, M.D., an associate professor of surgery and director of the Breast Cancer Surgery Multidisciplinary Fellowship at NYU Langone Medical Center, previously told HuffPost Style, “there is certainly no evidence that sleeping with bras is helpful or harmful. 

The cancer rumor in particular began with the 1995 book Dressed to Kill, which included claims that daily wear of tight-fitting bras increased risk of breast cancer  by constricting the lymphatic system, thereby trapping "toxins" in the body, Shape magazine reported. But there is no actual science whatsoever to back up this claim.

And in general, wearing a bra doesn't seem to have any effect on breast cancer risk. A recent case-control study published in the journal Cancer Epidemiology, Biomarkers & Prevention could find no association between breast cancer risk and bra-wearing among postmenopausal women.

“The risk was similar no matter how many hours per day women wore a bra, whether they wore a bra with an underwire, or at what age they first began wearing a bra," study researcher Lu Chen, MPH, who is a researcher in the Public Health Sciences Division at Fred Hutchinson Cancer Research Center, said in a statement.

On the flip side, there don’t seem to be any real benefits to wearing a bra to sleep — it’s not like doing so will keep your breast perky  HuffPost Women reported. Instead, time, gravity, pregnancy and breastfeeding are the usual culprits when it comes to breast changes like sagging.

However, women with large breasts (say, a D cup or higher) might want to wear a bra at night for the support, HuffPost Style reported.

If you do choose to wear a bra to sleep, you might want to opt for a soft one without an underwire. As Nemours’ Teen Health website points out, wearing a too-tight bra (or wearing a bra that digs into your skin) can lead to breast irritation or make you have trouble sleeping.