1. Sweaty 
There are some special bras designed specifically for sleep, usually made of nylon or cotton material that can make your skin ‘breathe’. But if you wear a regular bra to sleep, the sweat and moisture will stay inside the bra. This can cause itching and in extreme cases can cause injury.
2. Restlessness during sleep 
Regular bra (worn during the day) is specifically designed to support the breast and gives a beautiful shape. Bra like this are usually tight and toned so uncomfortable when worn while lying down or sleeping. Women who still wear a tight bra during sleep may have tickled and did not sleep soundly.

3. Insomnia 
In extreme cases, wear a bra while sleeping also can be one factor in insomnia because your body is not free to breathe.

4. Breast cancer risk 
Scientists from Sydney Singer and Soma Grismaijer his wife in 1991, once wrote in his book ‘Dressed To Kill: The Link Between Breast Cancer and Bras’, which contains about women who want to avoid breast cancer should wear a bra in the shortest time possible and preferably less than 12 hours per day. “The best time to rest his breast without a bra is during sleep. Do not sleep with a bra,” said Sydney Singer, as quoted by Chetday.

According to the Sydney Singer, use a bra for too long can increase the temperature of breast tissue and women who wear bras had higher levels of the hormone prolactin (hormone that functions to stimulate the milk glands) is higher. Both of these can affect the formation of breast cancer.

In addition, too often uses bra bra is too tight or use dangerous to health because it can also restrict the flow of lymph in the breast. Normally, lymph fluid wash waste material and other toxins, and also remove him from the breast.

Now now, do you think of wearing bra tonight when you sleep (:? Like what written above, there is this type of bra which specifically made for you to wear when you sleep. If you don't have that kind of bra, better off buying one, go naked (half, I mean), or simply wear another singlet/cloth inside (if you don't want others to see your tut tut tut). It's your call. Though, I always prefer girls take the last choice. *fingers crossed*!!