An irregular or abnormally long menstrual cycle may be linked to an early death, research suggests.
Periods make up part of the menstrual cycle, occurring when a non-pregnant woman sheds her uterus’ lining by bleeding from the vagina.
Most women have their period around every 28 days, however, a healthy cycle can range from 21 to 40 days.
An irregular or long menstrual cycle has been linked to everything from ovarian cancer and heart disease to type 2 diabetes and even mental health problems.
To better understand how it may impact mortality, a team of Harvard scientists looked at more than 79,000 women over 24 years.
The women who reported “always” having “irregular” cycles were more likely to die prematurely, defined as under 70.
The same risk applied to those who claimed their cycle usually lasted 40 days or longer.
Regular periods are considered an indicator of good health.
Nevertheless, irregular or long menstrual cycles are common among women of a reproductive age, the Harvard scientists wrote in The BMJ.
This has been linked to a host of diseases, which is thought to come down to a “disrupted hormonal environment, chronic inflammation and metabolic disturbances”.
With little being known on whether this impacts mortality, the scientists analysed thousands of women – with an average age of 38 – who took part in the Nurses’ Health Study II.
The women – who had no history of heart disease, cancer or diabetes – reported the usual length and regularity of their menstrual cycle at 14 to 17, 18 to 22 and 29 to 46 years old.
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Over the next 24 years, 1,975 of the women died before 70, of whom 894 lost their life to cancer and 172 to heart disease.
Among the women who reported always having an irregular cycle between 29 and 46 years old, 1.68 died “per 1,000 person years”.
This is compared to one death per 1,000 person years for those who had “very regular” cycles.
Similar results occurred for the other two age groups.
“Person years” take into account the number of people in a study and the amount of time each participant spends in the trial. For example, a study that followed 1,000 people for one year would have 1,000 person years of data.
The results further revealed the women who reported their usual cycle length was 40 days or more when 18 to 22 or 29 to 46 years old were more likely to die prematurely than those who claimed to have a cycle length of 26 to 31 days.
This remained true after the scientists took into account other factors that can affect mortality, like weight, lifestyle and family medical history.
The smokers with irregular or long menstrual cycles were slightly more likely to die prematurely, the results found.
A stronger link was found between dying from heart disease than cancer or another cause.
Despite the women having to recall their previous periods, which may have been inaccurate, the scientists maintained their results “emphasise the need for primary care providers to include menstrual cycle characteristics throughout the reproductive life span as additional vital signs in assessing women’s general health status”.
Other experts generally welcomed the study, but pointed out it does not prove cause and effect.
Socioeconomic factors, which do not appear to have been accounted for, may also influence a woman’s menstrual cycle.
“All of the participants in this study were nurses, some of whom will have worked very irregular hours,” said Dr Jacqueline Maybin from the University of Edinburgh.
“Shift work, particularly nightshifts, has been shown to have a significant impact on long-term health.
“Disruption of the circadian rhythm [body clock] has also been shown to affect menstrual regularity, with shift workers more likely to have irregular and long menstrual cycles.”
Another expert stressed women with an irregular or long cycle should not panic.
“This is an interesting paper, but it is perhaps not that surprising to see an association between irregular and long menstrual cycles and earlier death given the known link between oestradiol (the main oestrogen hormone in women) levels, menopause and cardiovascular disease,” said Dr Kim Jonas from King's College London.
“What this study will hopefully achieve is to raise awareness about menstrual irregularity, increase education, and encourage women and doctors to consider the menstrual cycle when assessing health.
“However, this study does not mean that all women who have experienced irregular menstrual cycles should be concerned.
“There is a lot more research to be done in this area and many factors are likely to be at play.”
Watch: Five period facts a woman should know