Women who have their uterus removed for reasons other than cancer may be at a greater risk of suffering a heart attack or stroke, suggests a large new study.

The risk appears to rise even higher for women who also have both ovaries removed. However, the Swedish researchers stop short of saying that taking out either the uterus or the ovaries can actually cause cardiovascular disease.

"Hysterectomy itself is a really safe procedure," senior researcher Dr. Daniel Altman of the Karolinska Institute told Reuters Health. "But some surgeries can be associated with risks that don't immediately show up, rather raising risks in the long term."

"That's something to at least consider before doing something irreversible," he added.

One in three women in the U.S. will undergo a hysterectomy, or the permanent removal of the uterus, at some point in their lives, for reasons ranging from fibroids or endometriosis to chronic pelvic pain. Cancer is rarely what prompts the surgery, although removal of the ovaries is commonly used for ovarian cancer prevention.

Meanwhile, cardiovascular disease — including heart attack, coronary heart disease and stroke — remains the number one killer of women.

To determine if there might be a link, Altman and his colleagues studied more than 800,000 women with and without hysterectomies over the course of three decades. On average, women were followed for about 10 years.

After accounting for several factors that might explain differences in risk — such as a woman's financial situation and the age at which her hysterectomy was performed — the researchers found that a woman who underwent a hysterectomy before age 50 had a nearly 20 percent higher risk of developing cardiovascular disease compared to a similar woman who still had both her uterus and her ovaries.

In women who had hysterectomy and also had their ovaries removed, cardiovascular risk was more varied - it could equal that of a women without any surgeries or rise to more than double that of a woman with only a hysterectomy.

The timing of the two surgeries appeared to play a significant role, report the researchers in the European Heart Journal.

For example, of 100 women under the age of 50 who had their ovaries removed before or at the same time as a hysterectomy, about four went on to develop heart disease, a stroke or a heart attack over the course of 10 years. On the other hand, about two of every 100 women with hysterectomy who had their ovaries removed at a later time developed cardiovascular disease. This was a similar rate to women who had neither procedure.

Given the large size of the study, the team was also able to tease apart the effects of the surgeries on specific types of cardiovascular disease. "We found that the risk was there whether you looked at stroke or heart attack or heart failure," noted Altman.

The researchers did not find the same relationships among women aged 50 or older when they had their hysterectomies, however.

Altman suggested that the hormonal changes that take place after the organs are removed might be to blame for the increased risks seen in the younger group. Prior research has shown that removal of the uterus can disrupt blood flow to the ovaries, which generate estrogen. Removal of the ovaries is known to trigger early menopause, which itself has been linked with an increased risk of cardiovascular disease.

"We're adding risks here," said Altman, noting that his team previously tied hysterectomy to other health problems including incontinence and kidney cancer.

"If we add all of these together," he suggested, "I think we're talking about a procedure that causes a great deal of morbidity, and even mortality."