Women with a history of irregular menstrual periods may have a higher risk of developing heart disease than do other women, a new study suggests.

The study, which followed more than 23,000 Dutch women for a decade, found that those who said they'd typically had irregular periods in the past were 28 percent more likely than women who reported regular monthly periods to develop heart disease.

There was no increased risk seen among women who reported regularly long menstrual cycles (30 or more days between periods) or regularly short cycles (26 or fewer days between periods).

Despite their relatively higher risk, though, the large majority of women with irregular periods did not develop heart problems during the study period. Of the roughly 4,000 women who reported a history of irregular periods, 150 were diagnosed with coronary heart disease over the next 10 years.

Just over 17,000 study participants reported having either regular monthly periods (between 27 and 29 days) or regularly short cycles. Of those women, 530 developed coronary heart disease.

The women were 50 years old, on average, at the start of the study.

It's known that women with a condition called polycystic ovary syndrome (PCOS) have higher risks of heart disease and type 2 diabetes than other women their age. In that disorder, the ovaries produce higher-than-normal amounts of male hormones and menstrual periods are irregular or completely absent.

The new findings suggest that even in the absence of PCOS, less-extreme irregularities in the timing of menstrual periods may be related to heart disease risk, according to the researchers, led by Dr. Gerrie-Cor M. Gast of the University Medical Center Utrecht in the Netherlands.

The potential reasons, however, are unclear. Since estrogen is believed to have a generally protective effect on the heart and arteries — and PCOS is marked by hormone imbalance — Gast's team measured hormone levels in a subgroup of their study participants.

They found no evidence that altered hormone levels explained the association between irregular periods and heart disease risk. Nor did factors such as body weight, high blood pressure, or high cholesterol account for the link.

Both PCOS and very long menstrual cycles — at least 40 days between periods — have been linked to increased risks of type 2 diabetes, which is a heart disease risk factor.

In this study, women with irregular periods tended to have a higher risk of type 2 diabetes than those with monthly periods; however, the association was not statistically significant — meaning the finding may have occurred by chance.

More research, according to Gast's team, is needed to confirm the current findings, and to uncover the underlying reasons for the link. The authors, who could not be reached for comment, do not address what, if anything, might lower the risk of heart disease among women with irregular cycles, should these results hold up in future studies.