Women who have their last period before age 42 are two times more likely to have a stroke down the road than those who experience menopause later in life, according to a University of Michigan School of Public Health study. 

Most women go through menopause, which is marked by completing one year without periods, at an average age of 51.  Some, however, enter this transition years earlier. They may undergo surgery or a medical treatment that removes their ovaries or stops production of reproductive hormones including estrogen and progesterone. Some have other medical diagnoses that shut down hormone production early. When menopause happens before age 40, it's called premature menopause. The study, published in the February 2009 issue of Stroke, identified women who went through menopause before age 42 as the ones with increased risk.

According to Dr. Linda Lisabeth, PhD, author of the study, early menopause doubles the risk for ischemic stroke (the most common type--characterized by clogged blood vessels). The American Stroke Association states that about 144,000 people die annually from stroke.  Hundreds of thousands more are seriously disabled. 

Lisabeth followed 1430 women throughout a long-term study.  All were stroke-free until age 60, had gone through natural menopause, and none had used estrogen before menopause.  Out of that group, 56 went through menopause before age 42; 1299 experienced it between ages 42 and 54, and 75 completed menopause after age 55. 

The researchers followed the women until they had their first ischemic stroke, died, or had completed the 22-year follow-up. During that time, eight of the 75 late-menopause women had a stroke, 213 in the much larger middle group (age 42 to 54) did, and 13 of 56 of the early-menopause women did.

They adjusted for individual factors including age, blood pressure, diabetes, smoking history, and heart disease--and still discovered that those who went through early menopause were twice as likely to have a stroke than the other women.  While this small group only represents 4 to 5 percent of all women, it may present significant information about the link between hormones and cardiac health.

Researchers don't feel they have enough information yet to make a concrete connection.  Lisabeth said during an interview with US News and World Report, "Exactly how to explain the link remains unclear. The lower estrogen levels associated with menopause might play a role, but evidence on whether this is so is conflicting."

How can women reduce their risk for stroke?  By controlling other factors that may contribute to heart disease and stroke.  Those include maintaining a healthy weight and diet (including lots of fresh fruits and vegetables and less red meat), exercising, and most importantly, not smoking.  Women who smoke are at much greater risk for heart disease and stroke than non-smokers.  Getting screened for diabetes and heart disease are also key in preventing serious cardiac events.

The bottom line?  Living a healthy lifestyle and protecting your cardiac health are the best ways to offset any increased risks for heart disease regardless of when you enter menopause.