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An ongoing health study from Apple seeks to increase understanding of the menstrual cycle and how it is related to health conditions like infertility, heart health, and menopause. Miodrag Ignjatovic/Getty Images
  • The menstrual cycle is an important but understudied indicator of health.
  • The Apple Women’s Health Study is using an app to track people’s menstruation and how it relates to certain health conditions.
  • The study’s latest update has revealed several important insights into PCOS.
  • It also provides data about links between PCOS and heart health.
  • Experts say this study may help improve how these conditions are managed.

While it’s expected you’ll experience some variation in your menstrual cycle, there are certain signs that could indicate you need to see a doctor, including changes in the length, frequency, or heaviness of your period.

Although menstruation is a very important indicator of health, it’s often only checked during Pap smears or consults for birth control.

Dr. Shruthi Mahalingaiah, an assistant professor of environmental, reproductive, and women’s health in the department of environmental health at the Harvard T.H. Chan School of Public Health, said this is why the Apple Women’s Health Study, which she is a principal investigator on, is so important.

“Our study hopes to empower women to contribute longitudinal, scientific data as they go about their everyday lives, rather than only being able to gather fragmented data in a limited setting or during a doctor’s visit,” said Mahalingaiah.

The Apple Women’s Health Study is the first long-term, large-scale study of its type. It seeks to increase understanding of the menstrual cycle and how it’s related to health conditions like infertility, heart health, and menopause. The study is open to anyone who has menstruated at least once, regardless of gender.

Data for the study is being collected via the Apple Research App on study participants’ iPhones, Apple Watches, or both, giving researchers unprecedented access to users’ health data.

While the study is ongoing, the most recent update delved into findings related to polycystic ovarian syndrome (PCOS).

According to Dr. Erin Donnelly Michos, director of women’s cardiovascular health and associate professor of medicine at Johns Hopkins Medicine, who was not a part of the study, PCOS develops from an overproduction of male hormones, called androgens.

It can lead to symptoms like irregular periods, excess hair growth in a male-type pattern, acne, and difficulty with getting pregnant.

More than 37,000 people who were enrolled from the beginning of the study in November 2019 through December 2021 were included in the analysis.

Participants completed a medical history and answered questions about any gynecological conditions they had, their family medical history, and their heart health.

About 30,000 of them also completed a reproductive history survey answering questions about their past menstrual cycles.

Among participants, 12 percent reported having a PCOS diagnosis.

They reported they had received their diagnosis anywhere from 15 to 35 years of age, with the median age being 22.

Researchers also looked at family history of PCOS. They found that 23 percent of participants reported a family member, like a mother or sister, who had the condition. By comparison, only 5 percent of those without PCOS reported this.

Participants who had PCOS were also more likely to report that they had irregular or unpredictable periods after their first onset during puberty.

While 70 percent of participants without PCOS said their cycles became regular within 4 years of their first period, only 43 percent of those with PCOS reported this.

In addition, almost half of participants with PCOS (49 percent) reported they only achieved cycle regularity after using hormones. In contrast, 22 percent of those without PCOS required hormones to regulate their cycles.

While we often focus on PCOS as a condition that affects periods and fertility, it does have other effects throughout the body as well, including cardiovascular health, blood pressure, cholesterol, diabetes, and obesity.

Michos said people with PCOS are insulin resistant. This means insulin can build up in the body, she said, making it harder to regulate blood glucose levels.

Insulin resistance is a risk factor for diabetes, so those with PCOS are at greater risk of developing this condition, according to Michos.

It can also cause weight gain in the abdominal area, which in turn leads to higher levels of triglycerides and lower levels of HDL, the so-called “good” cholesterol.

These things are all linked to cardiovascular disease, Michos said.

“Studies suggest that women with PCOS have a twice as likely risk of a future cardiovascular event, like a heart attack or stroke,” she said.

However, the link between PCOS and heart conditions has historically not been studied in relation to the menstrual cycle, explained Mahalingaiah.

“The level of research being conducted by the Apple Women’s Health Study is important for having a better understanding of PCOS and its health impacts, including for people with PCOS and those that might have PCOS but do not know,” she said.

Thus far, Mahalingaiah and team has found that participants with PCOS have a higher prevalence of certain conditions that negatively impact heart health.

They found those with PCOS were nearly four times as likely to have prediabetes and three times as likely to have type 2 diabetes.

Chronically elevated blood glucose can harm blood vessels in the heart.

In addition, high blood pressure and high cholesterol were 1.7 times higher in those with PCOS.

High blood pressure can damage the blood vessels over time, while high cholesterol can clog and block blood vessels, also creating higher blood pressure and increasing the risk of heart attack and stroke.

The team also reported that a majority of participants with PCOS — 61 percent — were classified as having obesity, which is defined as having a body mass index (BMI) of 30.0 or greater.

Obesity can affect blood cholesterol and blood pressure, and increase the risk of developing diabetes.

Finally, irregular heartbeat was more common among those with PCOS, with 5.6 percent having this condition compared with 3.7 percent of those without PCOS.

“There are ways for people with PCOS or a heart condition to manage their symptoms,” said Mahalingaiah.

“Healthcare providers may recommend lifestyle changes to promote menstrual regularity and improve your heart health, including changing your exercise routine, eating more nutritious food, getting better sleep, staying hydrated, and taking care of your mental health,” she said.

She further noted that the insights her team is gathering could help reinforce the importance of preventive reproductive care in the treatment of PCOS.

Mahalingaiah added that by increasing access to clinics and encouraging lifestyle changes at the primary care level, healthcare professionals can provide better care to people with PCOS throughout their lifetime.