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Girls are getting their periods earlier – Expert Reaction

A new study of over 70,000 American women born between 1950 and 2005 has shown that girls are getting their periods earlier and they’re taking longer to become regular.

While the average age reduced by a relatively small amount, the percentage of girls whose first period would be classified as ‘early’ or ‘very early’ has nearly doubled, finds the Apple-sponsored study published in JAMA Network Open.

The SMC asked local experts to comment.

Associate Professor Michelle Wise, Department of Obstetrics and Gynaecology, University of Auckland, comments:

“This is an interesting study evaluating age at time of onset of first menstrual period. Over 71,000 American women who have an iPhone were asked to remember the age at which they had their first period (menarche) and how long it took before their cycles regulated. The women were categorised by year of birth, self-reported ethnicity and self-reported level of deprivation. The authors found that from 1950s/1960s up to early 2000s, the age of first period decreased from on average 12.5 years old to 11.9 years old. This age reduction was more pronounced for Black women than White women, and for women in more deprived areas than better off women.

“The proportion of women who experienced early menarche  (< 11 years old) almost doubled. Most women had their cycles regulate within 1-2 years (which is considered the ‘norm’), but a higher proportion of the younger women in the study took > 2 years compared to the older women. In a subset of women who recalled their weight at the time of menarche, the researchers concluded that being overweight or obese explained half of this variation.

“In my practice as a Gynaecologist in a large public hospital, we see many women every day with irregular menstrual cycles, and our routine questioning includes age of menarche and how long it took for cycles to become regular. Having irregular cycles is associated with long-term health conditions such as mental health, cardiovascular disease and breast cancer. In the gynaecologist office, we see heavy menstrual bleeding resulting in anaemia and poor quality of life, new diagnoses of endometrial cancer in women in their 30s and 40s, and couples having difficulty conceiving. The epidemic of obesity is contributing to this and not enough is being done at the societal and policy level to address it.

“I suspect we would see similar results here in NZ as we, like the United States, are a high income country. However, we would have to do a similar survey using our ethnicity and socioeconomic mix, otherwise it is difficult to know if we too would see similar variations in age of menarche over time. Research in NZ to date is scant. Researchers at University of Otago have published some studies on this topic. A prospective cohort study of 415 girls born in Dunedin, published in 1994, found age of menarche to be 12.9 years old. A prospective longitudinal cohort of 497 girls born in Christchurch, published in 2011, finding the average age of menarche to be 12.1 years old. They found an association between earlier menarche and increased risks of sexually transmitted infection and teenage pregnancy. National data were analysed of women who participated in the NZ Health Survey of 2014/2015, finding the average age of menarche to be 13.2 years. The authors considered implications for age-appropriate health education and support in intermediate schools. These studies cannot be compared to each other to look for an age trend, rather the national study would need to be repeated.”

No conflict of interst declared.

Dr Ben Albert, Paediatric Endocrinologist, Starship Children’s Health, Te Whatu Ora, and Senior Research Fellow, Liggins Institute, University of Auckland, comments: 

“This study from the United States included 70,000 women who used a research app on their iphone to enter information about when they had their first period, which is called menarche.

“The study showed that over 50 years the age of menarche has decreased by around 6 months, and it has become more common for women to have menarche very young (before the age of 9). This reflects girls going into puberty earlier than they used to.

“The biggest reason for these changes seems to relate to increasing body mass index, which mostly reflects body fat, and fits with the rise in childhood obesity seen in the US and many countries. Other factors may also be contributing such as environmental chemicals, pollutants, stress and diet.

“The study doesn’t perfectly reflect the population of the United States (or New Zealand), but the effect they describe is probably relevant to women and girls in New Zealand. A decreasing age of menarche is important as it is associated with a higher risk of some health problems such as cancers and heart disease, and girls with very early puberty often need specific treatment.”

No conflict of interst declared.