How does air pollution impact menstrual cycles? Clue partners with MIT and University of Colorado Denver on largest women's health study of its kind
Analysis of 2.2 million menstrual cycles tracked in Clue shows connection between pollution exposure and reproductive health
A large international study examining over 2.2 menstrual cycles from 92,550 users of the cycle tracking app Clue, has found that long-term exposure to fine particulate air pollution is associated with an increased risk of menstrual irregularities.
The findings, published in The Lancet Planetary Health, offer new insights into the environmental influences on reproductive health and mark one of the most comprehensive investigations to date into the links between air quality and menstrual cycle patterns.
Clue partnered with researchers from MIT’s Senseable City Lab and the University of Colorado Denver to examine cycles logged by users in 230 cities across the United States, Mexico, and Brazil.
The analysis focused on ‘PM2.5’, which is fine particulate matter known to penetrate deep into the lungs and bloodstream, and its potential impact on menstrual health.
Longer cycles, greater irregularities
While air pollution is widely recognised as a risk factor for respiratory and cardiovascular conditions, its effects on women's health - particularly menstrual health - have received comparatively little attention.
In this study, the researchers found that higher long-term exposure to PM2.5 was linked to an increased likelihood of abnormal menstrual cycles, particularly cycles that are longer than usual - a potential indicator of disrupted endocrine or reproductive functioning. Short-term exposure did not appear to have immediate effects, but patterns emerged when looking at cumulative pollution exposure over several cycles.
"Menstrual cycle length and variability are a vital indicator of women's health," said Priyanka deSouza, PhD, of the University of Colorado Denver.
"Research has shown that highly variable menstrual cycles can be associated with an increased risk of premature mortality, cardiovascular disease, type 2 diabetes, cancer, and infertility."
Dr Shruthi Mahalingaiah, of the Harvard T. H. Chan School of Public Health and Massachusetts General Hospital, said the study offered a unique lens on how air pollution might influence menstrual patterns.
“PM2.5 is already known to harm human health, especially the heart and lungs. This study shows that it may also affect ovulation and menstrual health.”
New avenues for reproductive health research
A key aspect of the study was its use of digital health data. Rather than relying on retrospective self-reporting as previous studies have done, the research for this study made use of longitudinal cycle tracking data from Clue users, combined with satellite measurements of air pollution levels. By using this anonymised cycle data from Clue app users, researchers were able to track changes over time.
"Dealing with personal and sensitive data always poses ethical challenges," said Fábio Duarte of MIT's Senseable City Lab.
"In this study we were very careful in dealing with such data sets, but we were able to highlight how environmental stressors can have such deep and personal effects."
Amanda Shea, Fractional Chief Science Officer at Clue, said the findings demonstrate the potential of digital health tools to fill longstanding research gaps.
"Clue is helping close the gender health gap by making large-scale research into women’s health faster and more feasible than ever before.
“By analyzing millions of de-identified cycles tracked in the app alongside environmental data, we've taken a new approach to exploring how external factors like pollution might influence reproductive health. This kind of research offers people meaningful insights into their bodies, helping them recognize patterns earlier and make more informed decisions about their health."
Implications for policy and personal health
The study adds to a growing body of evidence suggesting that environmental conditions can influence reproductive health outcomes, including preterm birth and infertility. It also reinforces calls for more stringent air quality regulations and greater focus on environmental justice.
As the climate crisis continues and pollution levels remain high in many urban centres, the researchers stress the need for further study into the biological mechanisms behind these associations.
In the meantime, Clue’s science team recommends that individuals who are concerned about air quality and menstrual health consider the following:
Monitor local air quality and reduce outdoor activity on days when pollution levels are high. Many regions provide daily air quality updates through environmental agencies or mobile apps.
Track menstrual cycles using a reliable app. This can help individuals identify patterns and detect irregularities early.
Seek medical advice if you notice changes in your cycle or experience symptoms that affect your quality of life. Bringing detailed cycle data to appointments can support more informed conversations with healthcare professionals.
Study methodology
The study examined data from 92,550 Clue users, who collectively logged over 2.2 million cycles between 2016 and 2020. Researchers matched cycle-level data with city-level PM2.5 concentrations, based on satellite-derived air pollution estimates.