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This condition causes pain all over the body and someone suffering with it may also experience extreme tiredness, muscle stiffness, trouble concentrating and problems sleeping. According to the NHS, it tends to affect women seven times more than men. There is no cure but symptoms can be relieved through medication, therapy and lifestyle changes.
The singer has opened up about her experience with the illness for the first time in her upcoming documentary. She was also forced to cancel a concert in Brazil because she was taken to hospital with "severe pain".