Background: Modifiable lifestyle factors exert a substantial influence on the development of various diseases. The COVID-19 pandemic necessitated the implementation of containment measures to mitigate the viral spread, which affected the maintenance of healthy habits., Methods: Changes in lifestyle factors (e.g. physical activity, nutrition, smoking, drinking alcohol) within a cohort of German women at increased risk of breast cancer (BC) or ovarian cancer (OC) were evaluated through an anonymous web-based survey. The self-reported assessment of mental health was conducted using the PHQ-4 questionnaire. This tool combines two items from the Patient Health Questionnaire for Depression (PHQ-2) and two queries from the Generalized Anxiety Disorder Scale (GAD-2). Potential predictors of lifestyle changes were determined via multiple logistic regression analysis. A heuristic model was employed to project potential long-term consequences on BC incidence., Results: During the pandemic, 41.6 % of respondents reported reduced engagement in physical activity (PA), whereas 14.3 % reported increased engagement in PA. A score ≥5 on the PHQ-2 scale emerged as an independent risk factor for reduced PA (OR 12.719; 95 % CI 1.089-148.549; p = 0.043). By the heuristic approach, we projected an increase of BC by 3384 cases in Germany by 2030, which is attributable to the alterations in PA patterns during the pandemic., Discussion: Impaired mental health during the pandemic constituted a risk factor for unfavorable changes in PA. Consequently, a surge in BC may arise due to decreased engagement in PA. Healthcare professionals must remain aware of the potential risk factors that facilitate adverse alterations in modifiable risk factors caused by pandemic-related contingency measures or similar future events., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Roxana Schwab reports a relationship with 10.13039/100004337Roche Pharma Schweiz AG Reinach that includes: non-financial support, speaking and lecture fees, and travel reimbursement. Roxana Schwab reports a relationship with 10.13039/100004325AstraZeneca AB that includes: non-financial support, speaking and lecture fees, and travel reimbursement. Roxana Schwab reports a relationship with 10.13039/100009947Merck Sharp & Dohme Corp that includes: speaking and lecture fees. Roxana Schwab reports a relationship with 10.13039/100019944Sanofi-Aventis Deutschland GmbH that includes: non-financial support, speaking and lecture fees, and travel reimbursement. Kathrin Stewen reports a relationship with 10.13039/100019944Sanofi-Aventis Deutschland GmbH that includes: speaking and lecture fees and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/100004325AstraZeneca AB that includes: board membership, consulting or advisory, funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/501100022274Daiichi Sankyo Inc that includes: consulting or advisory, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/501100003769Eisai Inc that includes: board membership, consulting or advisory, funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/100004312Eli Lilly and Company that includes: board membership, consulting or advisory, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/100009947Merck Sharp & Dohme Corp that includes: board membership, consulting or advisory, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/100008792Novartis Pharma AG that includes: board membership, consulting or advisory, funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with Pantarhei Bioscience BV that includes: board membership, consulting or advisory, funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/100004319Pfizer Inc that includes: board membership, consulting or advisory, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/100004337Roche that includes: board membership, consulting or advisory, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/100020124Seagen Inc that includes: board membership, consulting or advisory, funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/100004328Genentech Inc that includes: funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with Palleos Healthcare that includes: funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt reports a relationship with 10.13039/100013226Pierre Fabre SA that includes: funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Annette Hasenburg reports a relationship with 10.13039/100004325AstraZeneca AB that includes: board membership, consulting or advisory, funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Annette Hasenburg reports a relationship with 10.13039/100006436Celgene GmbH that includes: consulting or advisory, funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Annette Hasenburg reports a relationship with GSK that includes: board membership, consulting or advisory, funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Annette Hasenburg reports a relationship with 10.13039/100004319Pfizer Pharma GmbH that includes: consulting or advisory, funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Annette Hasenburg reports a relationship with Tesaro Bio Germany GmbH that includes: board membership, consulting or advisory, non-financial support, speaking and lecture fees, and travel reimbursement. Katrin Almstedt reports a relationship with 10.13039/100004337Roche Pharma Schweiz AG Reinach that includes: funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Katrin Almstedt reports a relationship with 10.13039/100004319Pfizer Pharma GmbH that includes: funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Katrin Almstedt reports a relationship with 10.13039/100004325AstraZeneca 10.13039/100024877AB that includes: funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Anne-Sophie Heimes reports a relationship with 10.13039/100004319Pfizer Pharma GmbH that includes: funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Anne-Sophie Heimes reports a relationship with 10.13039/100004337Roche Pharma AG that includes: funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Anne-Sophie Heimes reports a relationship with 10.13039/501100022274Daiichi Sankyo Inc that includes: funding grants, non-financial support, speaking and lecture fees, and travel reimbursement. Marcus Schmidt has patent #EP 2390370 B1 licensed to Licensee. Marcus Schmidt has patent #EP 2951317 B1 licensed to Licensee. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)