GoKawiilBMJ analysis warns cycle-tracking apps pose privacy and accuracy risks
A new peer-reviewed analysis in The BMJ examines digital cycle-tracking apps used by an estimated 50 million people worldwide to monitor menstruation, fertility and 'cycle syncing' habits. The authors, including Tulane's Katharine Lee, say these apps' predictions rely on self-reported bleeding dates rather than actual hormone measurements, making them unreliable for forecasting ovulation or fertile windows, and that they cannot diagnose menstrual disorders or the causes of painful periods.
GoKawiil's interpretation of the reporting above, not reported fact.
The findings suggest that popular wellness trends like 'cycle syncing'—tailoring diet and exercise to menstrual phases—are being marketed without solid scientific backing, according to the study authors. This could mislead users into making health or fitness decisions based on inaccurate app predictions rather than consulting medical professionals. The analysis may also renew scrutiny of the femtech industry's data practices and claims as it continues to grow in popularity.
- An estimated 50 million people globally use menstrual cycle-tracking apps.
- BMJ analysis finds no reliable scientific basis for 'cycle syncing' claims about diet, exercise or performance.
- Apps estimate fertility windows from self-reported data rather than actual hormone levels, limiting accuracy.
Source: cnet.com — Anna Gragert, 2026-09-29
Published there as: “Cycle-Tracking Apps Bring Substantial Risks to Users, Says New Analysis”
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