The age you got your period may increase your risk for heart disease and stroke. Find out why, and what you can do about it

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How old were you when you got your first period? We know you know-that milestone is something no woman forgets. That number impacts more than just your memories, though. Women who get their first period before age 10 or after age 17 are more likely to develop heart disease, stroke, and issues related to high blood pressure, according to a new Oxford University study. (See if you're also at risk for The Little-Known Heart Condition Plaguing Working Women.)

Be most thankful if you had your first visit from Aunt Flo at 13 years old: The massive study, published in the journal Circulation, looked at more than one million women and found those who started at this age had the lowest risk of developing heart disease, strokes, and high blood pressure.

Meanwhile, those who "became a woman" before age 10 or after age 17 had a higher risk of hospitalization or death-specifically, a 27 percent higher risk from heart disease, 16 percent higher risk due to stroke, and 20 percent higher risk due to complications associated with high blood pressure. More bad news for young bloomers: Previous research has also found starting your period at a young age ups your risk of breast and ovarian cancer. (Could the Pill Increase Your Risk of Breast Cancer?)

So what's the deal?

It's not just that you got your period so early, it's why you got it: Childhood obesity is associated with girls starting their periods at younger ages, says study author Dexter Canoy, M.D., Ph.D., a cardiovascular epidemiologist at the University of Oxford. And overweight, early-blooming kids tend to remain at unhealthy weight levels into adulthood. "Obesity and its adverse health effects-including hypertension, diabetes, and high cholesterol-may predispose these women to develop heart disease, other vascular diseases, and some cancers as adults," Canoy explains.

Hormonal factors may also be at play, especially when it comes to the increased risk for cancers. "Women who start menstruating at an early age often have more ovulations than women who start after age 17," says Cheryl Robbins, Ph.D., an epidemiologist at the Center for Disease Control, who authored a study on how the age at which women start their periods may impact their survival after ovarian cancer. "Repeated ovulations and hormone surges may cause genetic mutations that could contribute to ovarian cancer."

However, Canoy cautions that hormonal and weight factors only partly explain the relationship between earlier periods and disease risk. Your environment, lifestyle, and endocrine disruptors (compounds that can mimic certain hormones and potentially impact your health) all factor in to what age you first ride the crimson wave-all of which can also affect your long-term health. Canoy admits that researchers are stumped by the association between starting your period after age 17 and increased vascular health risks, so more studies are needed to better understand that connection, too.

What can you do about it?

While you can't go back in time and change the day you started your period, you may already be at less of a risk: Women who follow a healthy lifestyle (like you!), including eating a heart-healthy diet, never smoking, clocking at least 40 minutes of movement per day, and maintaining a BMI below 25, are more than fifty percent less likely to suffer a stroke than unhealthier ladies, according to a study published in the journal Neurology.

And if you're still working on those healthy habits, now's a good time to start: Losing just five to 10 percent of your current weight over six months can help lower your risk for heart and other related diseases (including those impacted by your first period), according to the National Institute of Health.

Don't forget the other healthy habits, either: Eating a balanced diet, getting plenty of physical activity, and managing stress have all been shown to reduce your risk of obesity, heart disease, stroke, cancer, and more. (Don't know where to start? Try the 7 Single Health Moves with Serious Impact.)