In recent years, researchers have investigated the impact of hormonal fluctuations on brain structure during the menstrual cycle, how the internal circadian rhythm affects menstruation, and how women experience increased mental agility during menstruation.
The representation of women in medical research studies and trials has increased over the years, with vital research now being conducted on the topic of menstruation and female puberty.
A recent US study published in the Journal of the American Medical Association (JAMA) identified that the average age of menarche – when menstruation begins – continues in a downward trend. This longitudinal study of menstrual cycles, gynaecological conditions and women’s health was conducted by Harvard Chan School, the National Institute of Environmental Health Sciences, and Apple. More than 71,000 women were enrolled through an app and were asked to recall when they began menstruation.
The study found that the average age of menarche and breast development is becoming progressively younger. The timing of menstruation is ordinarily determined by genetics and the environment; however, the pace at which the change in onset of early puberty has occurred has led researchers to consider other factors.
Research indicates that the earlier the age of first menstruation, the greater the risk of adverse health outcomes – including several cancers such as endometrial, ovarian, and breast. A 2020 research study identified the “potential effects of younger age at menarche on lower lung function, higher heel bone-mineral density, greater burden of psychosocial/mental health problems, younger age at first birth, higher risk of childhood sexual abuse, poorer cardiometabolic health, and lower physical activity”.
According to the HSE, most girls get their first period around the age of 12, though they can start between 10 and 16.
Dr Geraldine Connolly, a consultant gynaecologist with 25 years of experience in the field, believes there are several potential causes of early puberty. Dr Connolly says the “skin” in the vulva and vagina is mucous membrane, “like what we have in our mouths, nose and ears. We don’t use perfumes in these areas and so should avoid them on our vulvas and vaginas. Also, many of the products used contain multiple chemicals such as chlorine bleach and plastics which also should be avoided”.
A recent study in Endocrinology aimed to identify chemicals that could potentially activate or affect reproductive functions. Many of these chemicals and compounds are found in daily life, resulting in a potential trigger for early menstruation and puberty.
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In her workshops with gynaecological resource My Girls Gynae, Dr Connolly discusses the importance of avoiding perfumed sanitary products, advising the use of eco-friendly products – particularly if using tampons as these are in direct contact with vaginal mucosa.
“We advise on vulval hygiene, avoiding all soap and washes in the vulva,” she says. “Also avoiding things like bubble bath and bath bombs, which are stuffed with chemicals. Like the nose and mouth, the vulva should not be exposed to chemicals and feminine hygiene products which remove the vulval microbiome and make the area more prone to soreness and infection.”
Researchers continue to investigate additional environmental impacts that are more commonplace than in previous decades such as microplastics and ultra-processed foods.
A report in Animal Reproduction studied the impact of microplastics on female reproduction and early life, noting that further research is needed.
“Microplastics are everywhere in our environment,” says Dr Connolly. “In food wrappings, in skincare products, washes and cosmetics, and in the clothes we wear. Microplastics have been found in atheromatous plaques removed from blood vessels (the carotid artery) in people who are at risk of or have had strokes. Our children are increasingly exposed to these environmental toxins, and these may play a role in early puberty.”
Additionally, diet is known to be a factor in menstruation. A 2022 report in Nutrients identified that a “high intake of yogurt, longer duration of breastfeeding, and food insecurity, decreased the possibility of earlier menarche, while high intake of protein increased that risk. As a modifiable factor, diet and nutrients in infancy and childhood provide new insights into the future prevention of early puberty”.
Dr Connolly says ultra-processed foods, usually wrapped in plastic, are another environmental exposure.
“These are so common now in most people’s diet, leading to childhood obesity, which in turn leads to early puberty,” she explains. “Our children have never not been exposed to the chemicals in our food stuffs. Reading the label on many products is like a chemistry lesson – and is not real food, but put there to make food addictive to increase sales. Many of the multinational food companies were previously run by cigarette companies, so the bottom line is shareholder profits and not providing healthy food.”
On another note, Dr Connolly says the increase in polycystic ovarian syndrome (PCOS) and obesity in young people are “likely to be due to increased empty calories and chemical content which form a large part of the adolescent diet”.
The recent study in JAMA identifying the earlier age of menarche also noted that more girls are taking longer to reach a regular menstrual cycle, with irregular cycles being associated with health conditions such as PCOS.
Dr Connolly emphasises that the fact that further scientific research is needed should not be used as a counter argument to these environmental changes.
“There are studies showing microplastics in blood vessels, which is just the start of the story,” she says. “Big money, and political will, are needed to develop and run observational population studies with the power to give meaningful answers. Such studies are not designed to increase profits for big multinationals and will be very difficult to get off the ground.”
She says further investigation into early menarche and its drivers is vital to the health of younger populations, and increased investment in menstrual health research is required.
