The menstrual cycle is already known to impact women’s physical and mental health, but a new scientific study reveals that its duration may also affect the risk of cardiovascular disease.
A new analysis of more than 58,000 women shows that a cycle that is too long or too short – i.e. not between 21 and 35 days – is associated with a higher risk of developing certain heart diseases.
A regular menstrual cycle is often considered to last 28 days – an average that can range to over 30 days for some women, or around 20 days for others.
For the purposes of this study, researchers in China estimated the length of a so-called regular menstrual cycle to be between 22 and 34 days, reflecting “normal functioning of the connected hormone systems among the hypothalamus, pituitary gland and ovaries”.
Based on this, they analysed health data of 58,056 women, with an average age of 46 at the start of the study and no cardiovascular disease.
All data, including menstrual cycle length and regularity, were collected during four follow-up visits in 2006-2010, 2012-2013, 2014 and 2019, over a median follow-up period of 12 years.
Higher risk of cardiovascular disease
Published in the Journal of the American Heart Association, this research first revealed that 39,582 women had regular menstrual cycles, while 18,474 participants had irregular or absent cycles.
This is a higher rate than the latest data published by the US National Institutes of Health in 2017, which estimated the proportion of women with irregular menstrual cycles at between 14% and 25%.
But the main finding of this research is that irregular menstrual cycles, in this case considered too long or too short, are associated with a higher risk of cardiovascular disease, and more specifically heart attack or atrial fibrillation – a heart-rhythm disorder.
“The association between menstrual cycle characteristics and adverse cardiovascular outcomes remains unclear,” said senior author Huijie Zhang from Nanfang Hospital of Southern Medical University in China.
“Considering the increasing prevalence of heart disease – with 45% of women in western countries affected – and related mortality, there is a need to explore these risk factors.”
In detail, women with menstrual cycles shorter than 21 days or longer than 35 days were more likely to develop heart disease (19%) than those with cycles between 22 and 34 days, and also had an increased risk of atrial fibrillation (40%).
The researchers suggest that shorter menstrual cycles are more strongly associated with an increased risk of cardiovascular events (29%) than cycles lasting more than 35 days (11%).
The same applies to the increased risk of atrial fibrillation, at 38% for shorter menstrual cycles and 30% for longer ones, again compared with a cycle considered regular in length.
Importance of prevention
“Our analysis indicates that women with menstrual cycle dysfunction may experience adverse cardiovascular health consequences. Therefore, we need to raise awareness that individuals with irregular menstrual cycle patterns may be more likely to develop heart disease,” Zhang said.
“These findings have important public health implications for the prevention of atrial fibrillation and heart attack among women, and highlight the importance of monitoring menstrual cycle characteristics throughout a woman’s reproductive life.”
It should be noted, however, that the study has certain limitations, such as the fact that the regularity or otherwise of the menstrual cycle relies solely on the interpretation of the participants themselves.
Also, the researchers did not exclude the potential influence of the menopausal phase on said irregular menstrual cycles, or that the age of the women studied was relatively advanced (40-69 years).