Pelvic floor disorders have been linked to low levels of vitamin D. Here is an article from Medscape: Higher Levels of Vitamin D Linked to Lower Risk of Pelvic Floor Disorders.
It seems that vitamin D can improve pelvic muscle strength and reduce pelvic floor disorders including incontinence.
I know my mother had this issue. It seems that women who have more children, mother had nine, and are obese are more likely to have pelvic floor disorders. She also did not spend much time in the sun when she was not completely covered up.