Pre-diagnosis physical activity and mammographic density in breast cancer survivors.

PURPOSE: To investigate the association between physical activity (PA) and mammographic density in the year before diagnosis in a population-based sample of 474 women diagnosed with stage 0-IIIA breast cancer and enrolled in the Health, Eating, Activity, and Lifestyle Study.
METHODS: We collected information on PA during an interview administered at a baseline visit scheduled within the first year after diagnosis. Participants recalled the type, duration, and frequency of different PAs for the year prior to their diagnosis. Dense area and percent density were estimated, from mammograms imaged approximately 1 year before diagnosis, as a continuous measure using a computer-assisted software program. Analysis of covariance methods were used to obtain mean density across PA tertiles adjusted for confounders. We stratified analyses by menopausal status and body mass index (BMI) because these factors strongly influence density.
RESULTS: We observed a statistically significant decline in mammographic dense area (p for trend = 0.046) and percent density (p for trend = 0.026) with increasing level of sports/recreational PA in postmenopausal women with a BMI > or = 30 kg/m2. Conversely, in premenopausal women with a BMI < 30 kg/m2, we observed a statistically significant increase in percent density with increasing level of sports/recreational PA (p for trend = 0.037).
CONCLUSIONS: Both mammographic dense area and percent density are inversely related to level of sports/recreational PA in obese postmenopausal women. Increasing PA among obese postmenopausal women may be a reasonable intervention approach to reduce mammographic density.