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Menopause makes menstrual cycles longer and less predictable, study finds
The research analysed how cycle and period length, irregular cycles and menstrual-related symptoms change with age
Menopause can make menstrual cycles longer and less predictable, a large study by the women’s health app Flo has found.
The study, which used a dataset of 19 million women, found that from the age of 45, women experience a dramatic increase in cycle length and variability. Prior to 45, cycles progressively shorten, but as women approach menopause, their cycles become more erratic.
This phenomenon has rarely been documented, primarily due to the frequent exclusion of this age group from menstrual cycle research.
The research, according to Flo, has shown a “holistic picture” of the cycle changes that occur across the reproductive lifespan.
All women will experience menopause in their lifetime, and yet, the symptoms and cycle patterns of this life stage are often under-researched.
The study investigated cycle and period length, irregular cycles, the most frequent menstrual-related symptoms, and how all of these factors change with age. It showed:
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The proportion of individuals with irregular cycles was highest in participants aged 51-55 (44.7 per cent), and lowest in the 36-40 age group (28.3 per cent).
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Frequency of logging of cramps and acne was lower in older participants, while logs of headache, backache, stress and insomnia were higher.
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The length of the menstrual cycle and menstrual cycle related symptoms show clear age associated patterns.
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With increasing age, cycles get shorter and more variable until age 40-44. Periods are longest in women aged 18-25, with an average duration of 5.20 days. They then gradually get shorter and last, on average, only 5.06 days in women aged 41 to 45. After that, periods become longer again, but they also become much more variable in length than in any other age group, indicating transition toward menopause.
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Irregular cycles were most common among older women with nearly half of women aged 51-55 and nearly one in three aged 46-50 reporting cycle irregularity. This is in line with expectations as cycles become less regular during perimenopause.
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Across all ages users experienced similar common symptoms, with cramps being the most common symptom logged. Also in the top three were tender breasts and fatigue, but only up to the age of 45, when headache took the place of fatigue.
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With age, headache, backache, stress and insomnia were logged more often, as was happy mood, which peaked at age 50. Mood swings were highest among youngest and oldest women.
Dr Lubna Pal, professor of obstetrics and gynaecology at the Yale School of Medicine, said: “The importance of this study lies in the chronicling of menstrual cycle and symptom data for a large and diverse population of women spanning in age from early adulthood into perimenopausal years.
“Findings from this epidemiological approach based on real life data allow a more comprehensive perspective on the prevalence of menstruation related phenomenon, and if and how these may vary across stages of reproductive aging.
“The wide-ranging populations’ perspectives offered in this study can help enhance population awareness of what symptoms, if being experienced by a majority, could even be construed as ‘norm’, may even help lessen the trepidations and stigma attached to aging, and can enhance preparedness of healthcare givers in their approach to enquiry, assessment and efforts at optimising care of women across the lifespan.”
Adam Cunningham, senior research scientist on Flo’s science team and lead study author, added: “It was surprising how little research there is about women’s cycles and symptoms, with most research stopping at 40 or 45 years of age.
“At Flo, we are in a prime position to help address this knowledge gap given that we have the largest dataset when it comes to women’s menstrual cycle patterns and symptoms.
“Advancing our understanding of female reproductive health is a core part of our mission and with this research we are one step closer to closing this knowledge gap.”
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Scientists say they have ‘rejuvenated’ human eggs, in work that could improve IVF success rates for older women.
The team reports that an age-related defect causing genetic errors in embryos may be reversed by supplementing eggs with a key protein.
In eggs donated by fertility patients, microinjection of the protein cut the share showing the defect from 53 per cent to 29 per cent.
The findings were presented at the British Fertility Conference in Edinburgh by researchers from the Max Planck Institute for Multidisciplinary Sciences in Göttingen.
The technique is being commercialised by Ovo Labs, co-founded by professor Melina Schuh, who led the research.
The approach targets problems in meiosis, the process where eggs halve their genetic material before fertilisation.
In older eggs, chromosome pairs can loosen and separate too soon, leading to embryos with too many or too few chromosomes, known as aneuploidy.
The researchers found levels of a protein called Shugoshin 1, which helps hold chromosome pairs together, decline with age. Microinjections appeared to restore this “molecular glue” and reduce errors.
Professor Schuh said: “Overall we can nearly halve the number of eggs with [abnormal] chromosomes. That’s a very prominent improvement.
“Most women in their early 40s do have eggs, but nearly all of the eggs have incorrect chromosome numbers. This was the motivation for wanting to address this problem.
“What is really beautiful is that we identified a single protein that, with age, goes down, returned it to young levels and it has a big effect.
We are just restoring the younger situation again with this approach.
Declining egg quality is a major reason IVF success rates fall steeply with age.
UK figures show an average birth rate of 35 per cent per embryo transferred for patients under 35, dropping to 5 per cent for women aged 43 to 44.
Dr Agata Zielinska, co-founder and co-chief executive of Ovo Labs, said: “Currently, when it comes to female factor infertility, the only solution that’s available to most patients is trying IVF multiple times so that, cumulatively, your likelihood of success increases.
“What we envision is that many more women would be able to conceive within a single IVF cycle.”
The approach would not extend fertility beyond menopause.
The team is in talks with regulators about a clinical trial.
Dr Güneş Taylor, of the University of Edinburgh, who was not involved, said: “This is really important work because we need approaches that work for older eggs because that’s the point at which most women appear.
“If there’s a one-shot injection that substantially increases the number of eggs with properly organised chromosomes, that gives you a better starting point.”
Women with two to three children live longest, while having more than four is linked to shorter lives, research on biological ageing suggests.
The study also found timing matters, with pregnancies roughly between ages 24 and 38 linked to more favourable ageing and longevity patterns.
Somewhat unexpectedly, childless women showed faster ageing than women with a few children, though this may be explained by other lifestyle or health factors.
Doctoral researcher Mikaela Hukkanen, who conducted the study, said: “From an evolutionary biology perspective, organisms have limited resources such as time and energy.
“When a large amount of energy is invested in reproduction, it is taken away from bodily maintenance and repair mechanisms, which could reduce lifespan.”
The research, conducted by the University of Helsinki and the Minerva Foundation Institute for Medical Research, followed nearly 15,000 female twins born between 1880 and 1957. Participants completed a questionnaire in 1975 and have been followed regularly since.
A novel aspect was measuring ageing biologically using epigenetic clocks, which detect ageing-related cellular changes by analysing chemical markers in blood samples. These can identify signs of biological ageing years before death.
The epigenetic analysis of more than 1,000 participants supported the mortality findings, showing women with many children or no children were biologically somewhat older than their chronological age.
Dr Miina Ollikainen, who led the study, said: “A person who is biologically older than their calendar age is at a higher risk of death. Our results show that life history choices leave a lasting biological imprint that can be measured long before old age.
“In some of our analyses, having a child at a young age was also associated with biological ageing.
“This too may relate to evolutionary theory, as natural selection may favour earlier reproduction that entails shorter overall generation times, even if it entails health-related costs associated with ageing.”
The researchers emphasised that the findings apply only at population level and do not demonstrate cause-effect relationships.
Dr Ollikainen added: “An individual woman should therefore not consider changing her own plans or wishes regarding children based on these findings.”
An NHS GP and menopause specialist has urged women to do three monthly health checks, examining their chest, vulva and moles.
Dr Carys Sonnenberg, an NHS women’s health GP and founder of the Rowena Health Menopause Clinic, shared the recommendation on TikTok, suggesting the first of each month as a good time to perform the checks.
She said: “It’s the first of the month, so it’s a really good day to do your chest check, to do your vulva check, and also to examine any moles that you have on your body, not forgetting your head.”
“When you are looking at your body, it’s really good to know what’s normal for you.
“So the CoppaFeel! website has got some brilliant information, with teaching you how to examine your chest properly, and knowing what problems you might be looking for, and anything that you need to report to your GP.”
CoppaFeel! is a breast cancer awareness charity that encourages monthly chest examinations.
The charity states: “Be aware of changes to your breasts and chest that might be signs of breast cancer.
“Getting into the habit of checking your chest every month is an easy way to stay on top of this.
“It’s also important to understand that some of these changes happen naturally, like during your monthly cycle.”
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