Apple continues to share insights from its collection of health studies. Last week, the company shared insights from a hearing study based on iPhone and Apple Watch data. Today, the Apple Women’s Health Study team at Harvard T.H. Chan School of Public Health released a preliminary study update about women and their menstrual symptoms.

Medical research on menstruation has often been limited to studies of smaller sizes, which are not representative of the broader population. Through the Research app, the Apple Women’s Health Study invites women across the US to contribute to research simply by using their iPhone, and Apple Watch if they have one.

The landmark study allows for the collection of a comprehensive set of cycle tracking and other health data, strengthened through participant surveys, from individuals across various stages of their life, varying races, and throughout all US states and territories.

Harvard Chan School researchers’ preliminary analysis of data, from a cohort of the first 10,000 participants to enroll in the study and respond to a demographics survey, validates women’s experiences of a wide range of menstrual cycle symptoms including some that are less commonly known or discussed. The most frequently tracked symptoms were abdominal cramps, bloating, and tiredness, all of which were experienced by more than 60 percent of participants who logged symptoms. More than half of the participants who logged symptoms reported acne and headaches. Some less widely recognized symptoms, like diarrhea and sleep changes, were tracked by 37 percent of participants logging symptoms.

The study team will further investigate the preliminary data and submit a detailed analysis, including a breakdown of methods, for peer review and journal publication.

“Our study will help to achieve a more gender equal future, in which all people with menstrual cycles have access to the health services and menstrual products needed to feel safe and empowered,” said Dr. Michelle Williams, Dean of the Faculty at Harvard Chan School.

According to the company, the Apple Women’s Health Study is a first-of-its-kind research study that aims to advance the understanding of menstrual cycles and how they relate to various health conditions such as polycystic ovary syndrome, infertility, and menopause transition.

“These findings take us a step further in validating and destigmatizing period symptoms,” said Dr. Sumbul Desai, Apple’s vice president of Health. 

iPhone and Apple Watch users across the US can download the Research app to enroll in the study, conducted in partnership with Harvard T.H. Cha School of Public Health and the NIH’S National Institute of Environmental Health Sciences (NIEHS). Participants must be at least 18 years old and have menstruated at least once in their life.