Why More Girls Are Experiencing Early Periods and Irregular Cycles Than Ever in the U.S.

two girls by the water
Image credits: Roberto Nickson/Unsplash

A common misconception is that menstrual cycles only affect reproductive health, but in reality, they are indicators of overall health. Menstruation influences mood, energy, immune response, and blood sugar levels. Ensuring normal menstrual cycles is crucial for women’s health. However, a new study reveals worrying trends in the US.

A study conducted on 71,341 female iPhone users in the US born between 1950 and 2005 reveals that girls are experiencing early onset of periods (early menarche) and irregularities in their menstrual cycle. 

These changes increase health risks later in life, including cardiovascular diseases, cancers, and premature death.

“Early menarche is associated with an increased risk of adverse health outcomes, such as cardiovascular diseases, cancers, spontaneous abortion, and premature death.” the study authors said.

The shocking changes in menstrual cycle patterns

During the study, the participants were asked questions like: ‘At what age did you have your first menstrual period?’ And ‘How long did it take for your cycle to become regular?’.

Results showed a rise in early menarche from 8.6% to over 15% between 1950 and 2005. The average age for the first period decreased from 12.5 years (1950-1960) to 11.9 years (2000-2005). Additionally, 11.2% reported irregular cycles even after two years, with 1,375 adults still experiencing irregular periods.

“From the 1950 to 1969 birth years to the 2000 to 2005 birth years, the number reaching regularity within 2 years decreased from 3,463 to 4,075, and the number not yet in regular cycles increased from 153 to 1375,” the study authors note.

The researchers also studied menstrual cycle trends in individuals from different racial and ethnic groups. They found that while the early onset of periods and irregular menstruation is rising among all sociodemographic groups, the trends are stronger among participants who are Black, Asian, or of low socioeconomic status.      

What’s causing this change? 

The researchers have yet to find the exact causes driving these menstrual cycle changes. However, they believe that there is not one but possibly many factors at play. These include stress, pollution, drugs, alcohol, unhealthy diet, exposure to different chemicals, and traumatic childhood experiences, which are also known to adversely affect period cycles.

In other words, these concerning trends may be the product of our modern lifestyles.

Additionally, obesity which is a known risk factor for the early onset of puberty may also have a major role in triggering early menarche.

“The prevalence of childhood obesity has increased in the US leading to hypotheses on the potential role of obesity in the trends toward earlier menarche. However, whether obesity is the primary factor underlying the trends in menarche remains debatable,” the study authors said. 

The researchers mention that early body mass index (BMI, the ratio of a person’s weight to the square of their height) is connected to menstrual cycle changes. 

“Within a subset of 9,865 participants with data on BMI at menarche, exploratory mediation analysis estimated that 46% of the temporal trend in age at menarche was explained by BMI,” the study authors added.

However, further research is required to confirm this connection.

The study is published in the journal JAMA Network Open.

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