Do you have an irregular period? It could be an early warning sign of heart disease

Women with irregular periods seem to have a significantly higher risk of cardiovascular disease, a new study suggests.

Up to one-fifth of American women of childbearing age — about 12 million of them — experience an abnormal period that occurs when the length of a person’s menstrual cycle unexpectedly falls outside the normal range, usually less than 21 days or longer than 35 days .

Irregular periods can be an inconvenience for millions of women at best, but at worst they increase women’s risk of heart disease by 19 percent and atrial fibrillation by as much as 40 percent, according to a team of researchers in China.

The study followed more than 58,000 women for 12 years, after which researchers found that about 3.4 percent of women with irregular cycles developed cardiovascular disease, compared to about 2.5 percent of those with normal periods.

Dr. Huijie Zhang, a professor at China’s Southern Medical University and lead author of the study, said“These findings have important public health implications for the prevention of atrial fibrillation and heart attacks in women and highlight the importance of monitoring menstrual cycle characteristics throughout a woman’s reproductive life.”

An analysis of data from more than 58,000 women found that both short (less than 21 days) and long (more than 35 days) menstrual cycles were associated with a higher risk of developing heart disease, atrial fibrillation and heart attack

The comprehensive study reflected health data from more than 58,000 healthy women in the UK who reported their cycle length at the start of a 12-year follow-up period.

The menstrual cycle is counted from the first day of one period to the first day of the next.

The study, published in the Journal of the American Heart Associationdrew on extensive health data in the UK BioBank, a large-scale population health research initiative with in-depth genetic and health information from half a million UK participants.

The average age of the participants, none of whom had cardiovascular disease at the start of the study, was 46 years.

After 11 years and eight months, researchers recorded 1,623 cardiovascular “events” among the participants, including 827 incident cases of coronary artery disease, 199 heart attacks, 271 strokes, 174 cases of heart failure, and 393 cases of atrial fibrillation, or irregular heartbeat that can lead to blood clots.

More than 1.7 percent of women with irregular cycles developed coronary artery disease (CHD), a result of plaque buildup on the walls of the arteries that then restricts the flow of oxygen-rich blood to the heart.

But only 1.3 percent of women with regular periods developed CHD.

And about 0.6 percent of those with regular cycles developed atrial fibrillation, compared to nearly one percent of those with irregular cycles.

The link between irregular menstrual cycles and heart disease isn’t entirely clear, though previous research has found them to be strongly linked to several risk factors for heart disease, including high cholesterol, hypertension, and polycystic ovary syndrome.

Hormone fluctuations fundamental to the menstrual cycle also affect cardiovascular function. Estrogen, which drops after ovulation but gradually rises afterward, has a protective effect on the heart.

Estrogen helps tissues and blood vessels remain smooth and flexible, aids in healthy blood flow, keeps blood pressure low, raises HD (good) cholesterol, and absorbs harmful free radicals.

While irregular cycles are common, they are not healthy and actually reflect a malfunctioning hypothalamic-pituitary-ovarian axis, the tightly regulated network of systems that control female reproduction.

Dr. Zhang said, “The association between menstrual cycle characteristics and adverse cardiovascular outcomes remains unclear.

“Given the increasing prevalence of heart disease – with 45 percent of women affected in Western countries – and associated mortality, there is a need to investigate these risk factors.”