Vol. 16 | Does the menstrual cycle in PCOS change with age? Insights from 160,000 recorded cycles

This article discusses a study that analyzed the records of 160,206 total cycles from 15,586 participants in the Apple Women’s Health Study.

Based on the period start dates recorded by participants, the research team compared the following three groups:

• Individuals previously diagnosed with PCOS by a medical professional
• Individuals without a PCOS diagnosis, but who have had irregular cycles since menarche
• Individuals who have had relatively regular cycles since they were young

The group with PCOS included 1,842 individuals, providing records for 18,875 cycles. Periods involving hormone medication, pregnancy, or breastfeeding were excluded from the analysis, and differences across age groups—from under 20 to over 50—were examined.

In younger age groups, individuals with PCOS or a history of irregular cycles since menarche showed a tendency for longer cycles and greater variation in the number of days between periods compared to those whose cycles were regular from a young age.

However, an irregular cycle does not necessarily mean you have PCOS. Many factors influence the cycle, including stress, sleep, weight changes, exercise levels, thyroid conditions, and medications.

What is particularly interesting about this study is that for those with PCOS or those who originally had irregular cycles, the cycle tended to become shorter and less variable as they progressed from their 20s to their 30s.

The gap compared to those who had regular cycles from a young age gradually decreased with age. The experience of “It used to skip for two months, but now that I'm in my 30s, it comes every month” may not necessarily be unusual.

On the other hand, from the late 40s onwards, a tendency for increased cycle variability was observed in all groups again. It is thought that the menstrual cycle does not change in a straight line, but rather adjusts its rhythm in accordance with different life stages.

Even if your cycle has become more regular than before, it does not necessarily mean that your "PCOS is cured."

PCOS is evaluated based on more than just the menstrual cycle; it includes ovulatory status, symptoms related to androgens (male hormones), and ovarian findings. Furthermore, fertility and metabolic health, such as blood sugar and lipid levels, cannot be determined by whether or not your cycle is regular.

When talking about menstrual cycles, the number "28 days" is often used. However, not everyone’s cycle is 28 days, and even for the same person, it does not necessarily mean it will be exactly the same number of days every month.

The important thing is to know your own usual rhythm rather than trying to conform to someone else's average.

• It is extremely longer or shorter than usual
• It has suddenly become much more variable
• The amount of bleeding or the pain has changed
• Bleeding occurs at times other than during your period

To notice these changes, your own records are more useful than anyone else's "normal."

Menstrual tracking apps and smartphone health features are convenient tools for looking back at your own changes.

In addition to the start date, keeping records of the following information will be helpful when you see a doctor:

• Number of days bleeding continued and any bleeding outside of your period
• Bleeding volume and frequency of changing sanitary products
• Changes in pain or physical condition
• Changes in acne or body hair
• Significant changes in sleep, stress, or weight
• Whether or not you are trying to conceive

However, the predicted ovulation date or next period date displayed by an app is an estimate calculated from the records you input. Especially if your cycle is irregular, it may differ from your actual ovulation date. You cannot diagnose PCOS or the presence of ovulation based solely on app records.

If you experience any of the following changes, do not endure it thinking you "should wait and see"—please consult a gynecologist or other healthcare provider.

• Your period hasn't come for a long period of time
• Your cycle has suddenly become more irregular than before
• Bleeding volume has increased suddenly, or bleeding is prolonged
• Bleeding occurs at times other than during your period
• You have severe pain or symptoms that interfere with daily life
• You wish to conceive but your cycle is difficult to predict
• You want to discuss a PCOS diagnosis or examination

In this study, the PCOS diagnosis was self-reported by the participants, and the participants were primarily users of Apple products in the United States. Also, this is not a study that followed individuals over several decades, but one that compares records from different age groups.

Therefore, these trends do not necessarily apply to everyone or to the population in Japan exactly as they are. Even so, it is significant that these large-scale, real-life cycle records suggest that cycles for those with PCOS may not remain the same throughout their entire life.