Apple Women’s Health Study: What we know so far.

The Apple Women’s Health Study is a research initiative conducted in collaboration with the Harvard T.H. Chan School of Public Health and the National Institute of Environmental Health Sciences (NIEHS). This study aims to advance our understanding of menstrual cycles and their connection to various health conditions, including polycystic ovary syndrome (PCOS), infertility, and menopausal transition. The study is unique in its scope and scale, as it invites individuals who menstruate to participate by using their iPhones or Apple watches if they possess one.

Here are the key findings and highlights from the update:

1. PCOS and Uterine Health: The preliminary findings suggest that 12 percent of study participants reported a PCOS diagnosis. Participants with PCOS had more than four times the risk of endometrial hyperplasia (a precancerous condition of the uterus) and more than 2.5 times the risk of uterine cancer.

2. Cycle Regularity: Approximately 5.7 percent of participants reported that their menstrual cycles took five or more years to become regular after their first period. Participants in this group had more than twice the risk of endometrial hyperplasia and more than 3.5 times the risk of uterine cancer compared to those whose cycles became regular in less than one year.

3. Importance of Awareness: The findings underscore the importance of understanding the relationship between menstrual cycles, PCOS, and uterine health. The study encourages individuals to consult with healthcare providers if they experience persistent changes in their menstrual cycle over several months.

4. Future Research: The study team plans to conduct further analyses on this preliminary data for scientific publication, indicating that more insights may be forthcoming.

5. Previous Interim Updates: The Apple Women’s Health Study has previously shared interim research updates, highlighting the prevalence of cycle deviations, common menstrual symptoms, and the impact of COVID-19 vaccinations on menstrual cycles.

6. Cycle Tracking: The Apple Women’s Health Study allows participants to contribute to scientific research by enrolling through the Apple Research app. Participants can share their cycle tracking data, health data from their iPhones, and, if applicable, data from their Apple Watch. The app also collects information about personal and family history and lifestyle through occasional surveys.

7. Cycle Tracking on iPhone and Apple Watch: Apple offers Cycle Tracking features in the Health app on iPhone and the Cycle Tracking app on Apple Watch. These features enable users to monitor their menstrual cycles, symptoms, and ovulation test results. Users can also receive notifications about their upcoming periods or fertile windows.

8. Temperature-sensing Capabilities: New sensors in the new Apple Watch Series and Apple Watch Ultra allow users to receive retrospective ovulation estimates based on overnight wrist temperature data. This information can be valuable for family planning.

Apple Women's Health Study Wrist temperature. Courtesy @Apple

9. Privacy: The update emphasizes Apple’s commitment to privacy, stating that health and fitness data in the Health app is encrypted when the iPhone is locked with a passcode, Touch ID, or Face ID. iCloud backups of health data are also encrypted, and end-to-end encryption is applied when syncing Health app data to iCloud.

Overall, this update highlights the importance of understanding menstrual health and its connection to broader aspects of women’s health. The Apple Women’s Health Study aims to provide valuable insights in this area and encourage individuals to take an active role in tracking and managing their health.


MBChB (MUK), Graduate Fellow, Department of Physiology, Makerere University Founder and Content Creator Peer reviewer, Associate Editor

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