Menopause is, to put it politely, unpleasant. And while the average age at which most women experience the hot flashes, mood swings, night sweats, and sleep problems (seriously, what exactly did women ever do to be so lucky?) is 51, it's possible for changes to begin much sooner. "There's a very wide range for normal age of menopause, but it's considered 'early' when it occurs before 40," says Margery Gass, MD, executive director of the North American Menopause Society.
Most women affected by early menopause know it's coming: Chemotherapy, radiation therapy, and an oophorectomy (removal of the ovaries) are all common causes. But it can also be due to lifestyle, environmental, and genetic factors. And even though only 1% of women hit menopause before 40, the factors behind an early change also affect the risk for a handful of illnesses and diseases.